FAQs

Firearms

XM-15

Our AK Muzzle Brake will thread right onto your barrel and is quite effective in cutting down muzzle rise.

Sound suppressor / silencers are available that will attach to the barrels with 1/2" X 28 tpi threaded muzzles which thread directly onto the muzzle, that will attach to the A2 bird cage flash suppressors or to other flash suppressor/silencer couplings. 

If your barrel is 16" long it has a removable flash suppressor. If it is 14.5" long it will have a permanently attached suppressor the silencers will not fit. 

Bushmaster has the pre ban type threaded barrels. Please review firearm specifications carefully for each application.

Instructions on scope installation

Procedure

The procedure to sight in the rifles with A3 handles is basically the same as the A2 sight system listed in the owner’s manual. The A3 sight base has a shorter throw as the elevation stem of the base is not as long as the A2 sight base and can not be raised as high. Since the A3 sight has 1/2 MOA elevation instead of 1 MOA elevation you must click up twice on the elevation knob from the 6/3 mark to the "Z" for zero mark instead of one click used on the A2 elevation knob with the 8/3 mark.

To battle sight zero at 25 meters click up twice to the "Z" mark using the smaller aperture. Make elevation adjustments with the front sight post. Make the windage adjustment with the windage knob. The index marks are also twice the distance as the marks on the A2. Going past the 6/3 to the 4 mark again would be for 700 meters. It will not go high enough for 800 meters. The small aperture is still used for 300 and longer meter ranges while the larger aperture is used for the 0 to 200 meter range.

Removing and installing the A2 Rear Sight can be done by following these simple directions:

To Remove the A2 Rear Sight

Remove the lower receiver, bolt carrier and charging handle. Drive out the roll pin under the elevation knob with a 3/32 drift punch that retains the elevation spring. Catch the elevation spring when removing the drift punch. The A2 sight base can then be removed by turning the elevation knob clockwise. There will be a ball detent and a detent spring in the left side of the sight base that will also come out when removed so do not lose them. The two piece elevation knob will now slip out the side of the receiver. Here again is another ball detent and detent spring for the elevation knob that should be set aside. The index screw may be removed from the top index knob with a 1/16" allen wrench.

To Install the Rear Sight Assembly

Place the index knob on top of the windage elevation knob. Place the elevation spring and ball detent in the hole in the receiver then slip the elevation knob assembly into the slot in the receiver for it. The ball detent and spring may be compressed with a small flat bladed screwdriver until the elevation knob captures them.

Insert the detent spring and ball detent into the rear sight base and hold them in place with your finger. Insert the sight base into the receiver and turn the elevation knob counter clockwise until the sight base bottoms out. 

 

Start the 3/32" roll pin into the receiver just below the elevation knob. Turn the receiver upside down. Place the elevation spring into the sight base. The elevation spring must be compressed when installed. To make this easier the rear sight base elevation can be turned out about 22 clicks from the bottom but not so far that the slots in the threaded base do not line up with the retaining pin hole in the receiver. Compress the elevation spring with a small flat bladed screwdriver and tap in the retaining roll pin until the spring is captured. The roll pin must be on top of the spring and not pass through it. Tap the roll pin in with the drift punch until it is flush with the receiver. 

 

Turn the elevation knob so the sight base is all the way down to its last full click. Then turn it up one click and hold the lower elevation knob in that position while slipping the upper index knob around until the 8/3 index lines up on the left side of the receiver. Place the sight index screw on the 1/16" allen wrench. Then insert the screw into the hole in the sight base just ahead of the rear sight aperture. Turn the screw into the elevation knob until it bottoms out and locks the index knob to the elevation knob. Remove the allen wrench and check the elevation knob to see that moves without binding.

Procedures to remove or install an A2 stock.

To Remove the A2 Stock

  • To remove the A2 standard buttstock you need to remove the top screw in the buttplate. This is sometimes difficult as the screw has a dab of Nylock thread locker on it. 
  • Remove the screw with a large screwdriver with a square shank that fits the screw slot tightly. 
  • Use a wrench on the shank of the screwdriver to get extra leverage and the screw will come out. 
  • Slide the buttstock off the receiver extension tube. 
  • The take down detent spring will be sticking out of the receiver. 
  • Remove the spring and set aside until reinstalling a stock so it does not get damaged. 
  • Remove the buffer and action spring by pushing down on the buffer retainer. 
  • Remove the receiver extension tube with a 5/8" open end wrench being careful to keep the buffer retaining pin from flying out as it is under spring tension. 
  • Reverse the procedure to reinstall the stock assembly. 
  • When installing the receiver extension be sure that it captures the buffer retainer. 
  • When installing the take down detent spring compress it with the stock so that it does not get kinked. Install the top screw to hold the buttstock in place. 

To Install the A2 Stock

  • To install an A2 buttstock you need a minimum of a 5/8" open end wrench and a large flat bladed screwdriver. 
  • It is recommended to have a Lower Receiver Vise Block a 1/2" drive torque wrench and an Armorer's Wrench for the extension tube installation.
  • Install the buffer retaining spring and buffer retainer in the lower receiver. 
  • Thread the buffer extension tube into the receiver while pushing down on the buffer retainer until the extension tube rides over the buffer retainer to hold it in place. 
  • Torque the extension tube to 35-39 foot pounds. Install the take down pin, take down pin detent and take down detent spring into the lower receiver. 
  • Install the stock spacer onto the rear of the extension then slide the stock onto the buffer extension tube and carefully depress the takedown pin detent spring into the lower so it is not kinked. 
  • Install the A2 buttstock screw into the upper hole in the buttplate and tighten until the stock is tight on the receiver. 
  • The screw has a dab of Nylock thread locker on it so use a large screwdriver that fits the slot in the screw to keep it from getting damaged. 
  • Cock the hammer in the lower and slide the buffer and buffer spring into the stock extension.

The A2 upper receiver has 1 MOA, MOA = 1" at 100 yards, elevation adjustments and 1/2 MOA windage adjustments. The Military battle Sight Zero is done at 25 meters, 27.3 yards, by clicking up one click on the elevation knob and using the small aperture sighting the rifle in by adjusting the front sight post for elevation and the windage knob for windage.

 

When you click back down to the 8/3 mark the large aperture is used for targets from 0 to 200 meters. The small aperture will be zeroed in at 300 meters. By turning the elevation wheel up to the 4, 5, 6, 7 and 8 marks the rifle is zeroed for 400, 500, 600, 700 and 800 meters. These are approximations for those ranges and can vary with the ammunition and weight in grains of the ammunition as well being used. 

 

Many people will sight in at 25 yards with the small aperture then refine the zero at 100 yards. Using the small aperture will give you a better sight picture for accuracy at any range. With the ammunition being used count the clicks it takes to shoot zero at longer known ranges. Note the information in a log book until you can memorize them for quick compensation at different distances. Then use that information for your range adjustments.

 

Procedures for sighting in an A3 sight.

The procedure to sight in the rifles with A3 handles is basically the same as the A2 sight system listed in the owner’s manual. The A3 sight base has a shorter throw as the elevation stem of the base is not as long as the A2 sight base and can not be raised as high. Since the A3 sight has 1/2 MOA elevation instead of 1 MOA elevation you must click up twice on the elevation knob from the 6/3 mark to the "Z" for zero mark instead of one click used on the A2 elevation knob with the 8/3 mark.

To battle sight zero at 25 meters click up twice to the "Z" mark using the smaller aperture. Make elevation adjustments with the front sight post. Make the windage adjustment with the windage knob. The index marks are also twice the distance as the marks on the A2. Going past the 6/3 to the 4 mark again would be for 700 meters. It will not go high enough for 800 meters. The small aperture is still used for 300 and longer meter ranges while the larger aperture is used for the 0 to 200 meter range.

An A2 front sight post is square and has 4 detent notches around the base of the post. An A1 is round and has 5 detent notches around the base

Carbon build up can cause the gas tube to be difficult to remove. Turn the barreled upper receiver upside down and lightly clamp the gas tube in a 4" vise with the handguard cap against one side of the vise. Then you can lightly tap on the rear of the receiver with a plastic mallet which will drive the tube out of the sight base.

If anyone has applied Loctite to "seal" the gas system a propane torch should be used to warm that area to soften the Loctite.

If you have the standard round CAR handguards you would not remove the heat shield held in place with pegs to install the rail. Press the mounting screws through the vent holes until they engage the rail then tighten them. The screws will pull themselves through the holes when that is done. 

The M-4 handguards with double shields have notches cut into the sides which hold the shields in place. The shields should be pulled out of the notches on one side till they clear so they can be pulled out. Be careful not to bend the shields.

We have a 3 rail gas block with detachable front flip up sight or a gas block with integral flip up sight available that can be installed. 

 

The three rail gas block can only be installed on barrels that do not have a permanently attached flash hider or muzzle brake. To install the gas block the front sight base must be removed first. Remove the upper receiver from the lower. Remove the bolt carrier assembly, charging handle and handguards. Free float handguards are left in place.

 

Remove the gas tube by drifting out the roll pin in the front sight base with a 1/16" drift punch. Pull the gas tube back into the receiver until it clears the front sight base. Then remove it by pulling it forward by the front sight base and out of the receiver.

 

Install the gas tube into the three rail gas block with the gas hole in the end down towards where the gas port will be in the barrel. To install the pin it is best to make a slave pin holder. Drill a hole in the end of a piece of round steel stock with a number 48 (.076") drill bit just deep enough to hold the roll pin. Use the slave punch to start the pin and seat it with a 1/6" drift punch. It is easier if the gas block is supported on a piece of wood so that it is stable. 

 

Place the front sight base on a piece of wood to support it with the ejection side down to remove taper pins which come out left to right. Start the pins with a 1/4" drift punch to break the pins free then drift them out with a 1/8" drift punch. Tap the sight base off the barrel with a plastic mallet.

 

Install the three rail gas block with gas tube onto the barrel. With receiver upside-down place a level on the bottom of the receiver and the bottom of the gas block. With the parts leveled tighten the set screws for the gas block with a 3/32" Allen wrench.

 

Install the flip up front sight onto the gas block with a 7/64" Allen wrench. Reassemble the rifle. Sight in the rifle with the rear windage set in the middle. Adjust windage if necessary by loosening the set screws and moving the front sight. After the rifle is sighted in remove one set screw at a time and reinstall them with a drop of # 242 Loctite Thread Locker.

It would be an M4 profile barrel which is standard weight under the handguards but heavy weight from the front sight to muzzle with a notch for mounting an M203 grenade launcher. It uses the heavy barrel .750" diameter sight base.

Heavy barrels are heavy at the chamber end and taper to the muzzle using the .750" diameter sight base.

A standard barrel tapers sharply at the chamber to a lightweight diameter to the muzzle using a .625" diameter sight base.

The Dissipater barrels have removable flash suppressors so they can be changed. 

It is recommended that you use barrel vise jaw blocks for removing or installing compensators. 

A replacement crush washer is needed as they should not be reused.

The front sight base is held on by taper pins that have to be driven out. The front sight tower is also the gas block which is necessary to the operation of the rifle. We do offer what is called a "V-Match" barrel in which the sight tower is shaved off for use with optics. We also offer that service here if you want to have us mill off the front sight tower. Our charge for milling and refinishing sight bases is around $50.00. There are also other options such as gas blocks with front flip sights that allow you to still have an iron front sight. You can find those in our online store.

The differences between the A2 and A3 sights are that the A2 sight is installed directly into the receiver while the A3 sights are a part of a detachable handle. The sight base in the detachable A3 handle is shorter. The A2 sight is adjustable for 1 MOA elevation and 1/2 MOA windage. MOA ( minute of angle ) is 1" at 100 yards. The A2 elevation adjustment is good for out to 800 meters with an 8/3 index. The A3 sight is adjustable for 1/2 MOA elevation and windage with the elevation adjustment out to 600 meters with the 6/3 index.

Since the A3 handle is 1/2 MOA elevation adjustment you need to click up 2 clicks instead of 1 to the "Z" mark to set for 25 meter battlefield zero.

The differences between the A2 and A3 sights are that the A2 sight is installed directly into the receiver while the A3 sights are a part of a detachable handle. The sight base in the detachable A3 handle is shorter. The A2 sight is adjustable for 1 MOA elevation and 1/2 MOA windage. MOA (minute of angle) is 1" at 100 yards. The A2 elevation adjustment is good for out to 800 meters with an 8/3 index. The A3 sight is adjustable for 1/2 MOA elevation and windage with the elevation adjustment out to 600 meters with the 6/3 index.

 

Since the A3 handle is 1/2 MOA elevation adjustment you need to click up 2 clicks instead of 1 to the "Z" mark to set for 25 meter battlefield zero.

This porting - unique to our 16" barreled Dissipator model - utilizes a special gas block which we locate under the full size handguards. The Dissipator's gas system functions like our 16" barreled "" but offers the benefits of the (cooler) standard handguards and the correct "full-length" positioning of the sight base. The Dissipator's barrel is not a "cut-down" 20", as a length of barrel after the gas port is critical for correct gas system functioning.

PROBLEM:
CHECK FOR:
WHAT TO DO:

RIFLE WON’T FIRE

SELECTOR LEVER ON SAFE

IMPROPER ASSEMBLY OF FIRING PIN

 

 

 

 

 

 

 

 

 

TOO MUCH OIL IN FIRING PIN RECESS

 

 

 

 

 

 

 

 

DEFECTIVE AMMUNITION

 

TOO MUCH CARBON ON FIRING PIN OR IN FIRING PIN RECESS

 

 

 

 

 

 

 

PUT IT ON FIRE

ASSEMBLE CORRECTLY
RETAINING PIN GOES IN BACK OF LARGE SHOULDER ON FIRING PIN

 

WIPE OUT WITH PIPE CLEANER

 

REMOVE AND DISCARD

 

CLEAN

BOLT WON’T UNLOCK
DIRTY OR BURRED BOLT
CLEAN, OR SEE YOUR GUNSMITH

WON’T EXTRACT

BROKEN EXTRACTOR SPRING

DIRTY OR CORRODED AMMO

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CARBON IN CHAMBER

FOULING OR CARBON IN EXTRACTOR RECESS OR LIP

 

 

 

 

SEE YOUR GUNSMITH

REMOVE STUCK ROUND

PUSH OUT WITH CLEANING ROD

CLEAN CHAMBER

CLEAN EXTRACTOR

WON’T FEED

DIRTY OR CORRODED AMMO

DIRTY MAGAZINE

DEFECTIVE MAGAZINE

TOO MANY ROUNDS IN MAGAZINE

ACTION OF BUFFER ASSEMBLY IS RESTRICTED

MAGAZINE NOT FULLY SEATED

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CLEAN

CLEAN

REPLACE

TAKE OUT EXCESS

TAKE OUT BUFFER AND SPRING - CLEAN THEM

ADJUST MAGAZINE CATCH: PRESS MAGAZINE
CATCH BUTTON ON RIGHT SIDE

TURN CATCH CLOCKWISE TO TIGHTEN AND
COUNTERCLOCKWISE TO LOOSEN

TURN CATCH ON LEFT SIDE

DOUBLE FEED
DEFECTIVE MAGAZINE
REPLACE

WON’T CHAMBER

DIRTY OR CORRODED AMMO

DAMAGED AMMO

CARBON IN CHAMBER OR ON GAS TUBE

 

 

 

 

 

 

 

CLEAN

REPLACE

CLEAN

WON’T LOCK
DIRT, CORROSION, OR CARBON BUILDUP IN BARREL LOCKING LUGS

CLEAN LUGS

WON’T EXTRACT

FROZEN EXTRACTOR

RESTRICTED BUFFER ASSEMBLY

 

 

 

 

 

 

 

 

 

 

 

 

RESTRICTED MOVEMENT OF BOLT CARRIER GROUP

 

 

REMOVE AND CLEAN

REMOVE AND CLEAN

REMOVE, CLEAN, AND LUBE (BEFORE PUTTING BOLT BACK IN, MAKE SURE GAS TUBE FITS INTO CARRIER KEY AND THAT THE CARRIER MOVES FREELY)

SHORT RECOIL

CORRECT ALIGNMENT OF GAPS IN BOLT GAS RINGS

TIP: Gas Rings should be replaced every 3,000 Rounds

 

 

 

 

 

 

 

 

CARBON OR DIRT IN CARRIER KEY OR ON
OUTSIDE OF GAS TUBE

 

 

 

 

 

Q-TIP, PIPE CLEANER PIECES, OR OTHER DEBRIS STUCK INSIDE CARRIER KEY

 

 

 

 

 

 

 

 

 

“GAPS” IN THE 3 GAS RINGS SHOULD BE STAGGERED 120° AROUND THE BOLT BODY FOR MAXIMUM EFFECTIVENESS

Note: Third Gap not visible in this picture - position
on back side of bolt

CLEAN CARRIER KEY OR AROUND THE GAS TUBE

CLEAN OUT IF POSSIBLE OR HAVE RIFLE
CHECKED BY YOUR GUNSMITH

BOLT FAILS TO LOCK AFTER LAST ROUND

DIRTY OR CORRODED BOLT LATCH

 

 

FAULTY MAGAZINE

CLEAN - OR REPLACE - BOLT CATCH CHECK FOR BUFFER ENDCAP BACKOUT OR OBSTRUCTION
CHECK FOR FULL TRAVEL OF BOLT CARRIER

REPLACE

SELECTOR LEVER BINDS

NEEDS OIL

DIRT OR SAND UNDER TRIGGER

LUBRICATE WITH CLP

CLEAN

BOLT CARRIER “HUNG UP”

ROUND JAMMED BETWEEN BOLT AND CHARGING HANDLE AND/OR DOUBLE FEED

  1. REMOVE MAGAZINE.
  2. PUSH IN ON THE BOTTOM OF THE BOLT LATCH.
  3. WHILE PULLING DOWN ON CHARGING HANDLE, TAP THE RIFLE BUTT ON THE GROUND. BOLT SHOULD LOCK TO THE REAR.
  4. WHILE BOLT IS HELD TO THE REAR, ROUND SHOULD FALL THROUGH THE MAGAZINE WELL.

NOTE: IF THIS PROCEDURE FAILS, USE A SECTION OF CLEANING ROD TO PUSH THE BOLT FULLY TO REAR THROUGH THE EJECTION PORT.

COLD WEATHER SHOOTING…

If cold weather requires it, your Bushmaster can be shot with gloved or mittened hands. The Trigger Guard is designed to open and swing down allowing better access to Trigger when the shooter is wearing gloves or mittens.

  1. Push in Forward Trigger Guard Pin with Bullet tip to release Trigger Guard.
  2. Swing Trigger Guard down for shooting with gloves or mittens.

CAUTION: Be careful of accidental discharges when inserting gloved fingers into Trigger Guard area.

MAINTENANCE IN EXTREME WEATHER…

EXTREME COLD: Clean and lubricate Rifle in a warm room with Rifle at room temperature. Do not lay a warm Rifle directly on snow or ice. Moving Rifle from cold into warmth will cause condensation which could keep Rifle from functioning.

HOT, WET CLIMATES: Clean and lube Rifle more frequently in moist climates. Inspect hidden surfaces of Bolt and Carrier Assembly, Upper Receiver, and Chamber / Barrel Extension (Locking Lugs), and Lower Receiver and Receiver Extension Assembly (Buffer Tube) for rust or corrosion. Also pay close attention to the Spring Loaded Detents on the rifle. Wipe off any hand / finger prints on the Rifle as they can accelerate the onset of rust or corrosion.

HOT, DRY CLIMATES: Take extra care with cleaning and lubrication as rifle will be exposed to blowing sand and fine dust, and extreme temperature shifts (hot in the daytime, freezing at night). Corrosion is less likely to form on metal parts in a dry climate. Lightly lube functional parts only - too much lubrication can attract and hold dust and sand.

RAINS: DO NOT FIRE THE RIFLE IF WATER IS PRESENT IN THE BARREL. Excess pressure can cause the Rifle to explode. ALWAYS drain any water from Barrel prior to firing. Dry the Bore with a Swab and Cleaning Rod if wet.

308

Our Bushmaster O.R.C. (Optics Ready Carbine) has a 16M4 profile barrel and the flash hider is NOT permanently attached. It will come off with a proper fitting wrench.

Mil Std for the trigger pull is 5.5 to 9.5 pounds but they usually run about 6 to 7 pounds.

 

For use with the ARMS # 40 rear sight a taller sight post should be installed in the YHM-9360K front sight. If you use any of the BMAS rear sights the taller sight post is not needed.

 

You can install our BMAS folding front sight for V-matches with a simple Allen wrench. It's part number F1002416 can be ordered by calling our sales line at 1-800-998-7928.

The carry handle can easily be mounted once the riser blocks have been removed. 

 

A Williams Fire Sight replaces the front sight post in a forged front sight base and clamps to the front of the sight base. Sight bases and or gas blocks that are attached with taper pins are not interchangeable. 

 

A gas block with flip up sight or a # ARMS 41-B can be installed. Here are pictures of the ARMS flip up sight.

 

In order to mount those flip up sights the flash suppressor and gas block need to be removed. The gas block has taper pins that come out left to right or towards the ejection port side. The flash suppressor crush washer will need to be replaced as they should not be reused once they have been crushed. 

 

Another front sight option is a V-Match flip up sight that clamps around the existing gas block so no gunsmithing is required. 

 

The Trijicon sights can be installed in those front sights.

The A1 sights are adjustable for windage only. The windage knob requires a sight tool or the tip of a bullet to depress a detent to rotate the windage knob. The A1 flip sight has two small apertures at different planes. The unmarked aperture is used for 0 to 200 meters and the "L" marked aperture is used for longer ranges.

If it is preban style with a bayonet lug it will not fit over the factory gas block. A post ban style will without the bayonet lug. 

The trigger pull on the standard trigger should be somewhere between 5-7 pounds.

Immediate action in case of trouble…

IF YOUR RIFLE STOPS FIRING: Perform the following immediate actions…

  1. SLAP upward on magazine to make sure it's seated properly.
  2. PULL charging handle all the way back observe ejection of case or cartridge. Check Chamber for any obstruction.
    WARNING: DO NOT LOAD WITH A HOT CHAMBER. A ROUND MAY “COOK OFF” (meaning it may fire from the heat of the chamber).
  3. If cartridge or case is ejected or chamber is clear, RELEASE Charging Handle to feed a new round.
  4. TAP Forward Assist.
  5. Now FIRE..

If the Rifle won't fire, look for trouble and apply remedial action.

Remedial action…

WARNING: If your rifle stops firing with a live round in the chamber of a hot barrel, remove the round fast. However, if you cannot  remove it 10 seconds, remove the magazine and wait 15 minutes with the rifle pointing in a safe direction (always check that the “SAFE” direction remains safe during that time) This way you won't get hurt by a round cooking off.

Regardless, keep your face away from the ejection port while clearing the hot chamber.

If your rifle still fails to fire after performing steps 1 through 5 above, check again for a jammed cartridge case.

If your rifle still fails to fire, check the troubleshooting section in this manual, or take the rifle to a qualified gunsmith.

Bullet stuck in bore…

WARNING: If an audible “POP” or reduced RECOIL is experienced during firing, IMMEDIATELY CEASE FIRE! Then…

  1. Remove the magazine.
  2. Lock the bolt to the rear.
  3. Put selector lever on the SAFE position.
  4. Check for a bullet in the bore with a cleaning rod.

Do not apply the IMMEDIATE ACTIONS described previously. If a bullet is stuck in the barrel of the weapon, do not try
to remove it! Take the rifle to a qualified gunsmith.

Troubleshooting (continued)…

Problem...
Check For...
What To Do...

Won't Fire

Selector lever on SAFE.

Improper assembly of firing pin.

Too much oil in firing pin recess.

Defective ammunition.

Too much carbon on firing pin
or in firing pin recess.

 

Put it on FIRE.

Assemble correctly.
Retaining pin goes in back of
large shoulder on firing pin.


Wipe out with pipe cleaner.


Remove and discard.

Clean.

 

Bolt Won’t Unlock
Dirty or burred bolt
Clean or see a qualified gunsmith.

Won’t Extract
Broken extractor spring.

Carbon in chamber.

Fouling or carbon in extractor recess or lip.

 

See a qualified gunsmith.

Clean chamber.
 

Clean extractor

Won’t Feed

Dirty or corroded ammo.

Dirty magazine.

Defective magazine.

Too many rounds in magazine.

Action of buffer assembly is restricted.

Magazine not fully seated.

 

PRESS MAGAZINE CATCH BUTTON ON RIGHT OR LEFT SIDE

 

Clean.

Clean.

Replace.

Take out excess.

Take out buffer and spring; clean them.

Adjust magazine catch.

Double Feed
Defective magazine.
Replace.

Won't Chamber

Dirty or corroded ammo.

Damaged ammo.

Carbon in chamber or on gas tube.

 

Clean.

Replace.

Clean.

Won’t Lock

Dirt, corrosion, or carbon buildup in barrel locking lugs.

Clean lugs.

Won't Extract
Frozen extractor. 
Restricted buffer assembly.

Restricted movement of bolt carrier group.

Remove and clean.

Remove and clean.
Remove, clean, and lube. (Make sure gas tube fits into carrier key and that the carrier moves freely before replacing).

 

Short Recoil

Correct alignment of gaps in bolt rings.

 

Carbon or dirt in carrier key, or on outside of gas tube.

 

Q-tip or pipe cleaner pieces
stuck inside carrier key.

 

“Gaps” in the gas rings should be staggered 120 around the bolt body for maximum effectiveness.

Clean carrier key, or around area of gas tube.

Clean out if possible or have rifle checked
by a qualified gunsmith.

Bolt Fails to
Lock After
Last Round

Dirty or corroded bolt latch.

 

Faulty magazine.

Clean out if possible or have rifle checked by a qualified gunsmith.

Replace.

Selector
Lever Binds
Needs oil.
Dirt or sand under trigger.
Lubricate with CLP.
Clean.

Bolt Carrier
“Hung Up”
Round jammed between bolt and charging handle and/or double feed.

  1. Remove magazine.
  2. Point muzzle in safe direction. Engage safety if possible by pushing out takedown pin and manually cocking hammer. Close receivers.
  3. While pulling down on the charging handle, bang the rifle butt on the ground. Round should eject.

WARNING:

Keep clear of muzzle!

CAUTION:

After round is removed, bolt is under tension! 

ACR

Problem:
Check For:
What To Do:

Firearm won't fire

Selector Lever on SAFE.

Improper Assembly Firing Pin

 

Correct Barrel Installation

Bolt Not Locked In Chamber

Too Much Oil In Firing Pin Recess

Defective Ammunition

Too Much Carbon On Firing Pin Or In Firing Pin Recess

Put it on FIRE

Assemble Correctly - Retaining Pin Goes In Back Of Large Shoulder On Firing Pin

Remove and Re-Attach

Tap Forward Assist

Wipe Out With Pipe Cleaner

Remove and Discard

Clean

 

Bolt won’t unlock

Dirty or Burred Bolt

Barrel not properly installed

Cam Pin Not Installed

Clean, or See Qualified Gunsmith

Remove and re-attach

Install Cam Pin

Won’t extract

Broken Extractor Spring

Dirty Or Corroded Ammo

Carbon In Chamber

Fouling Or Carbon In Extractor Clean Extractor Recess Or Lip

Frozen Extractor

Restricted Movement of Bolt Carrier Group

See Qualified Gunsmith

Remove Stuck Round Push Out With Cleaning Rod

Clean Chamber

Clean Extractor

 

Remove and Clean

Remove, Clean and Lube

Won’t feed

Dirty or Corroded Ammo

Dirty Magazine

Defective Magazine

Too Many Rounds in Magazine

Magazine Not Fully Seated

Barrel not properly installed

Clean

Clean

Replace

Take Out Excess

Remove Magazine and Clean Magazine Well

Remove and re-attach

Double feed
Defective Magazine
Replace

Won’t chamber
Dirty or Corroded Ammo
Clean

Won’t unlock

Damaged Ammo

Carbon In Chamber

Dirt, Corrosion or Carbon Build Up in Barrel Locking Lugs

Barrel not properly installed

Replace

Clean

Clean Lugs

 

Remove and re-attach

Short recoil

Piston Binding in Gas Block

Alignment of Guide Block

Broken Gas Piston Spring

Properly inserted Action Assembly Spring

Proper Setting of Gas Regulator

Bent Gas Piston

Clean Gas Block

Re-align and tighten

Replace part

Realign Action Assembly Spring

Set Correctly for Unsuppressed or Suppressed fire

Replace part

Bolt fails to lock after last round
 

Faulty Magazine

Proper Setting of Gas Regulator

Replace

Set Correctly for Unsuppressed or Suppressed fire

Selector level binds
Dirt or Sand Under Trigger
Proper Assembly

Clean

Remove and Re-Assemble

Selector lever spins freely

Selector Lever Detent Plate

Engagement to Hammer Spring

See Qualified Gunsmith

Bolt carrier “hung up”
Double Feed
Bound Gas Piston

Remedial Action

Clean, Check for Guide Block Alignment

MAINTENANCE IN EXTREME WEATHER…

EXTREME COLD: Clean and lubricate Firearm in a warm room with Firearm at room temperature. Do not lay a warm Firearm directly on snow or ice. Moving Firearm from cold into warmth will cause condensation which could keep Firearm from functioning.

HOT WET CLIMATES: Clean and lube Firearm more frequently in moist climates. Inspect hidden surfaces of Bolt and Carrier Assembly, Upper Receiver, and Chamber/Barrel Extension (Locking Lugs), and Lower Receiver for rust or corrosion. Also pay close attention to the Spring Loaded Detents on the Firearm. Wipe off any hand/finger prints on the Firearm as they can accelerate the onset of rust or corrosion.

HOT, DRY CLIMATES: Take extra care with cleaning and lubrication as rifle will be exposed to blowing sand and fine dust, and extreme temperature shifts (hot in the daytime, freezing at night). Corrosion is less likely to form on metal parts in a dry climate. Firearm should not require any lubrication.

HEAVY RAIN: DO NOT FIRE THE FIREARM IF WATER IS PRESENT IN THE BARREL: Excess pressure can cause the Firearm to explode.

ALWAYS drain any water from Barrel prior to firing. Dry the Bore with a Swab and Cleaning Rod if wet.

Minimalist

BA50

300 BLK

Carbon Series

Problem:
Check For:
What To Do:

Won’t Fire

Selector lever on Safe

Improper assembly of firing pin retaining pin

 

Too much oil in firing pin recess

Defective ammunition

Too much carbon on firing pin or in firing pin recess

Put it on FIRE

Assemble correctly; goes in back of large shoulder on firing pin

Wipe out with pipe cleaner

Remove and discard

Clean

Bolt won’t unlock
Dirty or burred bolt
Clean or see a qualified gunsmith

Won’t Extract

Broken extractor spring

Dirty or corroded ammo

Carbon in chamber

Fouling or carbon in extractor recess or lip

See a qualified gunsmith

Remove stuck round - push out with cleaning rod

Clean chamber

Clean extractor

Won't feed

Dirty or corroded ammo

Dirty magazine

Defective magazine

Too many rounds in magazine

Action of buffer assembly is restricted

Magazine not fully seated

 

Clean

Clean

Replace

Take out excess

Take out buffer and spring. Clean them

Adjust magazine catch: turn catch clockwise to tighten and counter clockwise to loosen

Double Feed
Defective magazine
Replace

Won't Chamber

Dirty or corroded ammo

Damaged ammo

Carbon in chamber or on gas tube

Clean

Replace

Clean

Won’t Lock
Dirt, corrosion, or carbon buildup in barrel locking lugs

Clean lugs

 

Won’t Extract

Frozen extractor

Restricted buffer assembly

Restricted movement of bolt carrier group

 

Remove & clean

Remove & clean

Remove, clean, & lube. (before putting bolt back in, make sure gas tube fits into carrier key and that the carrier moves freely).

Short Recoil

Q-tip or pipe cleaner Pieces stuck inside carrier key

 

Alignment of gaps in bolt gas rings

 

Carbon or dirt in carrier key or on outside of gas tube

Clean out if possible or have rifle checked by a qualified gunsmith

Gaps in gas rings should be staggered 120° around the bolt body for maximum effectiveness

Clean carrier key or around area of the gas tube

 

Bolt Fails to Lock
After Last Round

Dirty or corroded bolt latch

Faulty magazine

Clean - or replace bolt catch. Check for buffer end cap backout or obstruction. Check for full travel of bolt carrier
Replace

Selector Lever
Binds

Needs oil

Dirt or sand under trigger

Lubricate with CLP

Clean

Bolt Carrier
“Hung up”

Round jammed between bolt & charging handle or is double feeding
Remove magazine. Push in on the bottom of the bolt latch.
While pulling down on the charging handle, tap the rifle butt on the ground. Bolt should lock to the rear.

Warning:
Keep clear of muzzle.

Caution:
After round is removed, bolt is under tension.

Note:
If this procedure fails, use a section of cleaning rod to push the bolt fully to the rear through the ejection port.

Problem:
Check For:
What To Do:

Won’t Fire
Selector lever on SAFE
Too much oil in firing pin recess
Defective ammunition
Too much carbon on firing pin or in firing pin recess
Put it on FIRE
Wipe out with pipe cleaner
Remove and discard
Clean

Won’t Extract

Dirty or corroded ammo

Carbon in chamber

Fouling or carbon in extractor recess or lip

Remove stuck round - push out with cleaning rod

Clean chamber

Clean extractor

Won't feed

Dirty or corroded ammo

Dirty magazine

Defective magazine

Too many rounds in magazine

Action of buffer assembly is restricted

Magazine not fully seated

Clean

Clean

Replace

Take out excess

Take out buffer and spring. Clean them.

Adjust magazine catch: turn catch clockwise to tighten and counter clockwise to loosen.

Double Feed
Defective magazine
Replace

Won’t Chamber

Dirty or corroded ammo

Damaged ammo

Carbon in chamber

Dirt, corrosion, or carbon buildup in barrel or bolt face.

Clean

Clean

Clean

Clean

Won’t Lock

Frozen extractor

Restricted buffer assembly

Remove & clean

Remove & clean

Won’t Extract
Restricted movement of bolt carrier group
Remove, clean, & lube.

Selector Lever Binds

Needs oil

Dirt or sand under trigger

Lubricate with CLP

Clean

Bolt Carrier
“Hung up”
Round jammed between bolt & charging handle or is double feeding

 
Remove magazine. Push in on the bottom of the bolt latch. While pulling down on the charging handle, tap the rifle butt on the ground. Bolt should lock to the rear.

Warning:
Keep clear of muzzle.

Caution:
After round is removed, bolt is under tension.

Note:
If this procedure fails, use a section of cleaning rod to push the bolt
fully to the rear through the ejection port.

Pistols

PROBLEM:
CHECK FOR:
WHAT TO DO:

BOLT WON’T UNLOCK
DIRTY OR BURRED BOLT
CLEAN, OR SEE YOUR GUNSMITH

WON’T EXTRACT

BROKEN EXTRACTOR

DIRTY OR CORRODED AMMO
 

CARBON IN CHAMBER

FOULING OR CARBON IN EXTRACTOR LIP

SEE YOUR GUNSMITH

REMOVE STUCK ROUND:
PUSH OUT WITH CLEANING ROD

CLEAN CHAMBER

CLEAN EXTRACTOR LIP / BOLT FACE

WON’T FEED

DIRTY OR CORRODED AMMO

DIRTY MAGAZINE

DEFECTIVE MAGAZINE

TOO MANY ROUNDS IN MAGAZINE

ACTION OF BUFFER ASSEMBLY IS RESTRICTED
MAGAZINE NOT FULLY SEATED

 

CLEAN

CLEAN

REPLACE

TAKE OUT EXCESS AMMUNITION

REMOVE BUFFER AND SPRING:
CLEAN THEM

ADJUST MAGAZINE CATCH:
PRESS MAGAZINE CATCH BUTTON IN FROM RIGHT
SIDE OF RECEIVER. TURN CATCH CLOCKWISE
FROM LEFT SIDE OF RECEIVER TO TIGHTEN AND
COUNTERCLOCKWISE TO LOOSEN.

DOUBLE FEED
DEFECTIVE MAGAZINE
REPLACE

WON’T CHAMBER

DIRTY / CORRODED AMMO

DAMAGED AMMO

CARBON IN CHAMBER

CLEAN

REPLACE

CLEAN

BOLT FAILS TO LOCK
AFTER LAST ROUND

DIRTY OR CORRODED BOLT CATCH

FAULTY MAGAZINE

CLEAN - OR REPLACE - BOLT CATCH. CHECK FOR BUFFER ENDCAP BACKOUT OR OBSTRUCTION CHECK FOR FULL TRAVEL OF BOLT

REPLACE

SELECTOR LEVER
BINDS

NEEDS OIL

DIRT OR SAND UNDER TRIGGER

LUBRICATE WITH CLP

CLEAN

General

The surface finish of the Bushmaster rifle - all mil-spec hard anodize on the aluminum or manganese phosphate on the steel parts - is slightly textured or "matte finished" so that it won't reflect light - a military necessity. Here are a few tips on maintaining this matte finish. 

 

FIRST: USE ONLY BLACK RAGS on the outside of your rifle. Black t-shirts are great for this. A white or red rag or shop towel will rub into the matte textured surface and leave blotches. If this happens, use a Teflon based oil to remove blotches. There is a clear nickel acetate sealant applied over the anodizing and the steel parts in the rifle are also final finished in nickel acetate. Some solvents in gun cleaning solutions will attack nickel finishes, so read the label on your solvent to be sure you won't damage that surface finish. 

 

SECOND: Get a non-drying motor oil. Any non-drying motor oil will do, as long as it doesn't have additives that might attack the nickel acetate sealant that we apply as a final protective coating. Believe it or not, non-drying motor oil leaves a great looking finish.

The new flash hider or muzzle brake would have to be welded on again.

The NATO Spec 5.56mm chambers have a longer "leade" or throat than the SAAMI Spec .223 caliber chambers. While it is safe to fire .223 caliber ammunition in 5.56mm rifles, ammunition designated as 5.56mm should not be fired in rifles chambered in .223.  Please refer to the caliber marking on your barrel to confirm your rifle’s caliber.

Lower receivers are same for the following calibers: 5.56,.204 Ruger, 6.8SPC, 7.62x39 and .450 Bushmaster. The 7.62 NATO is a larger receiver.

Yes, AR15 type receivers in different calibers are interchangeable with the .223 lower receiver like the .450 Bushmaster, 6.8 SPC etc., as long as the action is the same length. In addition to a 9mm upper a 9mm mag well block must be used.

A 7.62 X 39 Russian conversion will fit the .223 lower receiver but a 7.62 X 51 Winchester .308 action is too long to fit a .223 lower receiver. 

Yes, heavy barrels are better in that they take more heat without distortion and do not have barrel "whip" of the early G.I. barrels. There are now variety of barrel contours, fluting, etc. to suit the need of the shooter.

 

Many times we see "parts guns" made on our stripped lower receivers using less expensive inferior aftermarket parts from unknown sources, barrels are not marked for instance, and people sell them as complete Bushmaster rifles so the value is not there. We have seen parts such as plastic buffers full of lead shot, plastic delta rings, plastic mag catch buttons, A3 handles with unmarked one piece elevation wheels etc. 

 

If someone uses all Bushmaster parts to build a rifle the value is usually the same as factory rifles. 

 

Sometimes values are increased when quality parts are used to customize the rifles such as Picatinny handguards, pistol grips, buttstocks, back up iron sights, optics, competition triggers etc. 

 

The cost of saving is not as much as it used to be to build your own.

The semi automatic is the only military models that can be purchased by civilians. 

The only full automatic rifles that are transferable to civilians must have been manufactured before the 1986 National Firearms Act went into effect. Any full automatic rifles manufactured after the 1986 NFA Law went into effect can not be transferred to civilians and any semi automatic rifles can not be converted to full automatic for civilian use.

Yes, the Varminter upper can be installed on the M4 lower receiver assemblies.

Some basic tips for assembling lower receivers on your AR rifle. Assembling a lower receiver is not really that big a deal, it will, however, go much smoother if you make a few tools to help you along. 

Receiver Block:

vise block.PNG

The first thing that makes assembly easier is some way of holding the receiver while you are working on it. We sell an excellent tool for this, called a lower receiver vise block, but an old junk magazine with some wood stuffed inside it will work if you clamp it in something (a vise). The military manual has blueprints for some extra tools in the back, these can come in handy. Some of those tools we use here. 

Slave Punch:

Some other tools we use here are called slave punches. A slave punch is just a punch with a hole in the end to hold a roll pin and get it started in the hole it's supposed to go into. Brownell's (515-623-4000) sells these, or they are easy to make. We use a different slave punch for every roll pin in the rifle. Some pins are the same size, but as they go in different places, we use a different punch for each one, one with an end specially shaped so as not to leave a mark on the finish in that area. We make the ones we use here out of stainless round stock, but they can be made out of just about anything. These are what let us assemble without leaving marks all over the place. 

Manual:

The military manual shows all the assembly and disassembly necessary to work on these rifles in detail with illustrations. It is important to update your manual every few years, as the new changes keep coming. The new A-2 manual, for instance, has the complete section for the M-4 carbine, covering the tele-stock assembly and specific parts list. They keep changing things too, like the setting of the elevation dial on the A-2 rear sight. 

 

Common Problems:

Some common problems with assembly are forgetting to insert the disconnector spring, placing the tails of the hammer spring under instead of over the trigger pin, losing the takedown pin detents, and putting the bolt catch spring in the disconnector spring pocket. These are all very simple mistakes, but they will cause major malfunctions down the road. 

 

Fortunately, they are easy to fix, if you are looking for them. Installing the hammer spring backwards is another popular mistake. Not a problem, as it's easily corrected. Again, the manual or the assembly video will show you the mistake. Losing the buffer retainer and spring is another popular one. If you are installing or removing the stock assembly (or receiver extension), you have to hold on to that little sucker, or it will fly! Always support the ears of the trigger guard when installing Roll Pin with a piece of wood to prevent breaking off the ear.

 

Installing a barrel is really pretty simple. Solving some of the problems you can run into isn't. 

 

Probably the most common problem is excessive windage present after the installation. The rear sight will be cranked all the way to one side. This is one time the manual doesn't help much, most military armorers learn this trick early. 

Here's how to fix it:

  • Clamp the barrel in a vise, using barrel blocks. 

         

  • Line up the front sight carefully on a vertical line, just like the book says. 
  • First tighten up the barrel nut - hand tight, not torque to prevent damage to receiver. 
  • Now, look at your receiver. Chances are it's leaning off to one side -when compared to the front sight. 
  • Using a non-marring hammer, hit the side of the carrying handle, as near to the front as you can. This will rotate the receiver slightly to one side or the other. 
    • Here's the trick, hit on the side that the rear aperture is furthest away from. In other words, try to move the receiver towards the rear sight. Be careful, you don't have to slam it, just a firm tap will usually do the trick. 

 

If the barrel is straight, aligning the receiver forging with the front sight forging will usually put the windage adjustment right in the middle, and it takes about a minute to do it. Simple! 

 

One other trick we should mention is for when you are torquing on a barrel nut and everything locks up. A squeaking noise, then it's like it's welded right there. 

The surest way to break something is to keep trying to loosen it. This trick is incredibly simple.

  • Put the whole assembly in the freezer, and leave it overnight. This gets some differential expansion working for you. 
  • Pull it out the next day, and it will almost always come loose. 
  • We recommend using an action block, like the one we sell, and clamping on the receiver to prevent breaking the index pin when doing this.

         

  • A really good wrench, like the heavy duty one we sell, will prevent ruining the barrel nut.

       

If you shoot enough cheap ammo, it'll happen to you. The rifle is just ticking along, then BAM! The bolt is stuck forward and the magazine blows down out of the rifle. Looking up into the mag. well, you see a crack in the bottom of the bolt carrier. You've just had a case head separation. If you are shooting reloads or surplus ammo, you're out of luck. If you have factory ammo, and the box the shells came in, you can write a letter or call the factory, and they will tell you what to do. We have seen case head failures from overloaded ammo, and from bad brass. There is almost no difference in the result, though. When the case head fails in an AR, the gases flow back into the action. They usually bend or break the extractor, flow along the extractor slot, and crack or break the bottom pad of the bolt carrier. The gases vent out mostly through the mag well, usually wrecking the magazine on the way out. Sometimes the bolt cracks, sometimes it doesn't. In extreme cases, it can crack or break the barrel extension. Many times the bolt catch will break off and the upper receiver will crack by the ejection port. Usually the lower will survive, but sometimes they crack somewhere at the top of the mag well, usually in the front. The front half of the case will remain stuck in the chamber. This is a sure sign of an ammunition failure. If the rifle had failed, the bolt lugs would all be sheared off, the stock would be blown off, the gun would probably be blown in half. We've never seen it happen, and we hope we never do.

 

Cleaning and maintaining your rifle is an essential part of owning a firearm.  If you notice any blotches on the receiver after cleaning, here are some helpful tips:

 

The receivers on our XM-15 are bead blasted before anodizing, and that means they have a textured surface. Think of it like sandpaper, about 800 grit. If you rub a white cloth on a black piece of sandpaper, the cloth rubs off, leaving streaks or blotches. For a nice black sheen, use only black rags and non-drying oil like motor oil. For a matte finish, use black rags and Rem-Oil or "Break Free" with CLP. Either way, black rags will give you the look you want.

California Law does not allow the sale of Assault Weapons with a pistol grip and detachable magazine. Bushmaster is on the California Banned list.

The following links to California's Department of Justice may provide more specific details regarding California firearm laws.

Bushmaster does not permanently attach bird cage flash suppressors to the 14.5" barrels as the bird cage flash suppressors are not long enough to bring the barrel up to the 16" legal length.

The 14.5" barrels are available with permanently attached Izzy, Phantom or Phantom 2 flash suppressors for 16" legal length. They can be ordered as a V-Match barrel with milled gas block at no additional charge.

You can install the 6.8 SPC upper on the 5.56 lower receiver. The lower receivers marked 5.56, 6.8 SPC and .450 Bushmaster are all the same except for the caliber markings. When complete 5.56, 6.8 SPC or .450 rifles are manufactured the lower shipped with it is marked with that caliber. 

You should use the 6.8 SPC magazine that comes with the 6.8 SPC upper assemblies.

 

Subject: 6.8 SPC in .223/5.56 magazine

The two magazines use different followers as the rounds are different diameter even though they are the same overall length. If you load more than about 6 rounds of 6.8 SPC into a .223/5.56 aluminum magazine the body of the magazine swells so it is very difficult to insert into the receiver if you can and the rounds will not feed properly.

      

The 6.8 SPC magazines have stainless steel bodies that do not swell and the proper followers for reliable feeding.

The front sight base can be removed on 16" and longer barrels that do not have a permanently attached compensator. You must install a gas block or cut the front sight base down for a gas block.

There is no first stage adjustment to make it lighter. If it was made lighter by replacing the trigger competition spring with a standard trigger spring the trigger would never reset itself.

Our .308 is a scaled up version of the .223 therefore the uppers and lowers are not interchangeable.

 

The chrome lined barrel only comes with the barrel nut, handguard cap, front sight base with sight post and sling swivel installed. 

The complete barrel kits also include the Delta ring kit, gas tube & pin, handguards as well as the flash suppressor and washer for 16" and longer pre ban type barrels.

A chrome lined barrel will have about twice the life of a non chrome lined barrel of about 15,000 to 20,000 rounds. Chroming is done after a barrel is rifled and the process strips some metal from the barrel before being chromed to bring it back up to tolerances. The lands and grooves of the rifling are not as sharp as on a non chrome lined barrel and tolerances can vary depending on how much material was stripped and how much chrome was applied. 

The non chrome lined barrels are usually more accurate since bore tolerances can be machined to tighter specs. Most all competition barrels are non chrome lined. 

The trade off is that the non chrome lined barrels will have a life of 8,000 to 10,000 rounds.

All Bushmaster receivers have always been manufactured from forgings. Bushmaster does not manufacture cast lower receivers.

Our 6 position tele stock buffer tubes are the larger 1.14" diameter buffer tubes which are commercial spec.

Fluting (machining lengthwise grooves into the outer surface of the barrel) increases the surface area of the barrel - thereby allowing increased radiational cooling of the barrel mass. This process also adds to the "stiffness" of the barrel which enhances its accuracy. A third benefit of fluting is that the barrel is lighter after machining removes the steel in those lengthwise grooves. A fluted barrel will last longer, shoot straighter, and is considerably lighter than a standard heavy barrel. The accuracy gains would be most noticeable at longer distances or to the competition shooter, but for only $50 additional for most Bushmaster barrels, many feel that the benefits of fluting are well worth the cost.

The lower receiver assembly with pistol grip comes with the standard trigger assembly. It can be ordered with a two stage trigger installed as an option for an additional charge.

In our experience, the most accurate muzzle is the post-ban crowned muzzle. Many competition and target shooters we have talked with confirm this. As the bullet leaves the muzzle, you want - for greatest accuracy - to have no alteration of, or influence on, the bullet's flight. With an 11 degree competition crown, the gases behind the bullet flow out in an even pattern of dispersal at the instant that bullet exits the barrel. This affords the least chance of disrupting that bullet path.

The fluted Varminter models do not have a chrome lined bore. The bore and chamber are competition grade and the steel is 4150 Chrome Moly Vanadium.

 

Yes the bore and chambers of the 6.8 are chrome lined.

The block in Colt lowers prevents the use of M16 bolt carriers, but they will function with correctly machined AR carriers. It is illegal to use M16 carriers in AR15's. Bushmaster lower receivers do not have this block.

The V-Match flat top uppers come with come with the deeper feed ramps.

Front sight removal to install a V-Match floating hand guard is necessary, but it is not strictly a gunsmith's job. It does take special tools and a gentle touch. Call our customer service line and they'll talk you through the process. You can then determine whether you want to attempt it or not. The front sight is held in place with solid taper pins and, if they are not damaged in removal, they can be reused.

Yes, we include a set of modified M4 oval handguards with the kits. More room is needed for the offset spigot so the gas piston and operating rod are in-line with the receiver.

 

Gas piston conversion handguard

The gas piston system will not fit under most handguards. Extra clearance is needed as the gas spigot is offset so the gas piston and operating rod are in line with the receiver. 

The ARMS SIR # 50C and # 51C handguards fit with no modifications. 

The ARMS # 50M-CV does not fit. 

The LWRC handguard needs a very slight modification for barrel clamp clearance. 

 

The Daniel Defense specific gas piston handguard with removable top rail our part # DD-Omega7, not listed online yet, will fit with the conversion # GP-GSR for standard and M4 barrels. The Daniel Defense gas piston handguard will not fit the conversion # GP-GSR-HB for heavy barrels.

      

The gas piston conversion kit can be ordered less the modified M4 handguards by calling us at 1-800-998-7928.

 

Our 6.8 barrels used to have SAAMI chambers and 1/10 twist. They now all have Spec II with a 1/11 twist.

If you see 1/11 on the barrel it has a Spec II chamber.

 

We are often asked this question at Trade Shows and on our phone lines. And not to sound patronizing but we usually counter by asking "How well can you shoot?, because as most shooters agree, the gun is only a tool and the skill / experience of the operator is a crucial factor in the quest for accuracy.

We think we make a great "tool" The quality materials, quality control and craftsmanship we build into every Bushmaster rifle gives it the potential for exceptional accuracy. To back up that belief, we thought we'd show you some targets that were sent in recently by a gun writer friend of ours - Steve Malloy. Steve writes for SWAT Magazine among others, and he had asked to test a Bushmaster in "V Match DCM" configuration. By way of description, this would be a rifle with a flat-top upper receiver, our tubular aluminum free-floating handguard and our extra heavy DCM Competition barrel (20", 1 in 8" twist). This rifle also featured our 2 stage competition trigger, and for accessories, Steve requested a Harris Bi-Pod setup and our Bushmaster Modular Accessories System Mini Risers to get his scope comfortably up off the flat-top upper.

This combination - in Steve's capable hands - yielded some impressive results. See for yourself, and remember that these were shot at 300 yards...(the scale of the scans varies as you'll see by the differing bullet hole sizes.)

Replacing the gas rings is recommended approximately every 3,000 rounds.

How to:

  • To replace the gas rings use a prick punch or knife point to lift one end of the gas ring and pull them off the bolt and discard them. 
  • To install the new ones place the gas ring over the back of the bolt on top of the flange for the rings. 
  • Start the gas ring by placing one end into the groove then work it around until the other end will pop into the groove. 
    • Do not spread the gas ring any more than necessary to slip it into the groove. 
  • Alternating the center gas ring when installing them will help them not to have a gap line up. 
  • The new style gas rings have the gap at an angle so even if they line up with the center ring reversed there will be no continuous gap. 
  • The gaps should be staggered 120 degrees apart at 12:00, 4:00 & 8:00 o'clock for example. 

 

NOTE: When installing the bolt into the bolt carrier with new rings installed, push it in until some resistance is felt where the gas rings need to be compressed to fit the smaller diameter inside the carrier. When that resistance is felt wiggle the bolt up and down as well as sideways to compress the rings as the bolt is being pushed all the way in.

 

The upper receiver may be stamped with an "L", "O" or "Y" on the rear of the takedown lug. Some uppers are not stamped with that code. The "A" is a forging house mark that may be used by many manufactures.  

 

If the second stage of the trigger is lost or the trigger does not return an adjustment of the 2nd stage spring plunger is required.

A trigger that will not return has a point to point engagement that does not allow the sear surfaces to slide by each other.

Each rifle, lower receiver assembly or trigger kit is supplied with a specialty .035" allen wrench in a Zip lock bag with trigger instructions.

Remove the lower receiver from the upper receiver. Cock the hammer back and put the safety selector on "SAFE". Use the .035" allen wrench to loosen the locking set screw for the tall threaded spring plunger in the left hand side of the safety selector. Put the safety selector on "FIRE". With a pair of needle nose pliers turn the spring plunger in clockwise until the second stage is felt and the trigger will reset itself. If the trigger does not return recock the hammer before readjusting spring plunger in some more until the second stage is felt and the trigger will reset itself when released. Put the safety selector back on "SAFE" and tighten the locking set screw.

ONLY Molybdenum grease or paste should be used to lube the sear surfaces. Any petroleum based oil or grease will cause the trigger to feel sticky and grabbing when the first stage is taken up. To clean and lube the sear surfaces remove the lower receiver from the upper receiver. With the hammer in the forward or fired position drift the hammer pivot pin out with a 1/8" drift punch. The hammer can be lifted out of the receiver and the sear surface cleaned. Use a cotton swab to clean the nose of the trigger in place in the lower receiver. Apply molybdenum paste to the sear surface of the hammer and just below it. Reinstall the hammer and pivot pin into the receiver. Be sure that the long doglegs of the hammer spring are on top of the trigger pivot pin and against the inside of the receiver to keep the trigger pivot pin from walking out.

How to change a welded muzzle brake to a flash hider.

 

Details:

Bushmaster muzzle brakes and flash hiders that are permanently attached are done so in the following manner: The unit is threaded onto the barrel, blind hole drilled in two places into the threads, holes are pinned, pins are welded over, welds are ground flush and the complete barrel assembly is then sent to finish.

      

Free float handguards that replace the barrel nut can not be installed on these barrels.

      

In order to remove the unit without damaging the muzzle the pins must be drilled or ground to below the threads before removal of the unit. This will usually damage the flash hider or brake so that it can not be reused. The threads of the muzzle may still have some damage that would require chasing with a die before replacing the flash hider or brake. 

      

In order to bring the barrel back to legal length the replacement flash hider or brake must be long enough to bring the total length to 16" or longer overall length. It must also be permanently attached according to BATF standards by high temperature silver soldering or pinning and welding. An A2 bird cage is not long enough to do that. The Phantoms and Izzy flash suppressors are long enough.

      

Bushmaster is not set up to do individual piecework on barrels so it would need to be done by a gunsmithing shop or a machine shop. 

      

If you want to interchange muzzle brakes and suppressors you will need to get a pre ban type 16" barrel.

Bushmaster does not have a .22LR conversion kit available. If you type Ceiner .22LR conversion into your search engine you will find sources for them. They come with a bolt carrier assembly that replaces the .223 bolt carrier and a .22LR magazine.

With the right tools, installing the A1 sight should be a fairly straightforward process.

To install the sight you should have a 1/16" drift punch, ballpeen hammer and a flat bladed screwdriver to fit the windage screw. It is recommended that you make a roll pin slave punch to start the 1/16" roll pin. We use a piece of round steel rod and drill a 1/16" hole in the end just deep enough to hold the end of the 1/16" roll pin near the edge.

Place the leaf spring into the corresponding rectangular slot of the upper receiver. Place the flip sight aperture on top of the leaf spring so that you can see the "L" mark of the long range aperture. Insert the windage screw into the left side of the receiver and start it into the flip aperture. Use the flat bladed screwdriver to turn the screw so that the aperture is centered in the receiver. The left side of the windage screw should be all the way in against the receiver. Place the windage drum spring in the hole on the right side and place the detent on top of it. Push the windage drum onto the windage screw and compress the detent and spring. Align the hole in the windage drum with the hole in the windage screw. Insert the 1/16" punch as a slave pin to hold then together. Use the slave punch to start the 1/16" roll pin into the windage drum. The roll pin is then set even with the windage drum.

Instructions for installing an Ambi Safety.

Procedure

To install the Ambi safety you need to first remove the old safety by removing the pistol grip with a 3/16" allen wrench. The grip has the safety detent spring in the right side. If the safety detent does not drop out of the receiver move the safety back and forth a few times until it drops to clear the safety. The safety can then be removed from the receiver with the hammer cocked.

Install the new Ambi safety into the receiver. Install the safety detent and the pistol grip with the safety detent spring. Be sure that the detent spring is not binding by moving the safety to the on and off positions and check for positive locking in those positions. 

If the roll pin has not been started in the right side lever, then install the roll pin so that it is just protruding to the inside of the lever. Use the roll pin to locate the lever's position and install the 4-40 screw with a 1/16" allen wrench. Then use a drift punch to seat the roll pin.

Follow the steps below to install a 1 piece Aluminum Handguard on your AR rifle.

 

To install an aluminum one piece handguard you need a vice, Armorer's action block, Armorer's wrench and a strap wrench. 

 

Remove the handguards. The front sight base/gas block with gas tube must be removed by drifting out the two taper pins from left to right. Place the sight base/gas block on a piece of wood for support with the ejection side of the receiver down. Start the pins with a large drift punch to loosen them then drift them out with an 1/8" punch. Tap the base off with a plastic mallet. Place the upper in the action block in a vice and remove barrel nut with Armorer's wrench on a breaker bar. Remove the barrel nut and handguard cap. 

 

Lube the threads of the aluminum handguard with Tetra grease and turn on the handguard as tight as you can by hand. Tighten the tube with the strap wrench until the next one of the holes for the gas tube lines up with the hole in the receiver. Install the sight base/gas block with gas tube onto barrel. Install the taper pins right to left as far as they will go by hand with the ejection side up and then tap them home.

 

To remove the aluminum handguard you need to remove the gas block with gas tube by drifting out the taper pins. The taper pins drift out left to right. Place the gas block on a piece of wood for support with the ejection side of the receiver down. Start the pins with a 1/4" drift punch then drift them out with a 1/8" drift punch. Tap the gas block with gas tube off the barrel with a plastic mallet. 

 

Place the upper receiver in an Armorer's action block and then the block in a vise. Remove the handguard with a strap wrench by unscrewing the handguard counter clockwise.

Installing and removing a barrel will take some specialty tools and following these directions.

Install a Barrel

Specialty tools required are an Armorer's wrench, 1/2" drive torque wrench ( installing bbl nut ), 1/2" drive breaker bar ( removing bbl nut ), Armorer's Action block or Barrel Vise Jaw Blocks, 4" vise minimum and a 1/16" drift punch.

  • To install a barrel you need to place the barrel in vise jaw blocks or the receiver in an Armorer's Action Block in a 4" vise. 
  • The threads on the upper receiver should be lubed with molybdenum disulfide grease. 
  • Install the barrel with delta ring kit installed into the upper receiver with the index pin of the barrel extension in the index slot of the upper receiver. 
  • The barrel nut should be torqued on to 32 to 45 ft lbs using an Armorer's barrel wrench. 
  • If needed back off and reinstall until a notch in barrel nut lines up with gas tube hole in receiver for the installation of the gas tube. 
  • Never back off the barrel nut for this alignment. 
  • Install the gas tube into the receiver through the front of the receiver until it clears the front sight base. 
  • Then align the tube and insert it into the front sight base. 
  • Install the gas tube roll pin and handguards. 
  • Check the gas tube alignment with the bolt carrier without the bolt installed. 
  • If the alignment is correct the bolt carrier key will not bind on the gas tube.

Remove a Barrel

Specialty tools required are an Armorer's wrench, 1/2" drive torque wrench ( installing bbl nut ), 1/2" drive breaker bar ( removing bbl nut ), Armorer's Action block or Barrel Vise Jaw Blocks, 4" vise minimum and a 1/16" drift punch. 

  • Remove the barreled upper receiver assembly from the lower receiver assembly. 
  • Remove the charging handle and bolt carrier assembly. 
  • Remove the handguards. 
  • Use the 1/16" drift punch to drift out the gas tube roll pin in the sight base. 
  • Pull the gas tube back into the receiver until it clears the handguard cap then pull it out of the receiver past the front sight base. 
  • To remove the barrel nut place the barrel in Barrel Vise Jaw blocks or the receiver in an Armorer's Action block in the vise. 
  • Remove the barrel nut with the Armorer's wrench on the 1/2" drive breaker bar. 
  • The barrel will now pull out of the upper receiver.

Follow the steps below to install or remove the B.M.A.S. handguard.

 

To install an aluminum handguard you need a vise ( 4" minimum ), Armorer's action block, Armorer's wrench and a strap wrench. Remove the handguards. The front sight base/gas block with gas tube must be removed by drifting out the two taper pins from left to right. Place the sight base/gas block on a piece of wood for support with the ejection side of the receiver down. Start the pins with a large drift punch then drift them out with an 1/8" punch. Tap the base off with a plastic mallet. Remove the handguard cap. Place the upper in the action block in a vice and remove barrel nut with Armorer's wrench on a breaker bar.

 

The B.M.A.S. three piece handguard is installed by placing the upper receiver in an Armorer's Action Clamp in a vise. The barrel nut threads are lubed with Tetra Grease and the nut installed with an Armorer's Wrench to 32 to 45 ft lbs until one of the holes in the nut lines up with one of the holes in it and the upper receiver for the gas tube. The locking ring is turned on all the way on to the rear of the barrel nut and the forward tube is threaded onto the barrel nut. To index the tube it is backed off to about 45 degrees from the rails lining up. The locking ring is turned until it contacts the tube. A strap wrench is then used to tighten and align the tube onto the locking ring. The gas block or front sight base with gas tube is then installed. Taper pins should be installed right to left as far as possible by hand then set with a drift punch while the sight base is supported on a block of wood with the ejection side of the receiver up.

 

To remove the forward tube the upper receiver is placed in an Armorer's Action Clamp in a vise. A strap wrench is used to loosen the forward tube. After it is loose it can be unscrewed from the barrel nut. To reinstall the locking ring is turned on all the way on and the forward tube is threaded onto the barrel nut. To index the tube it is backed off to about 45 degrees from the rails lining up. The locking ring is turned until it contacts the tube. A strap wrench is then used to tighten and align the tube onto the locking ring.

 

It is not recommended to remove the handguard for cleaning unless absolutely necessary and definitely not without the proper equipment so that it can be reinstalled correctly.

The Harris Bipod Adaptor has a rectangular piece with a female threaded nut that fits inside the handguard on top of the heat shield. After the bottom handguard is removed it is placed in the second vent hole back from the front on carbine handguards and the third hole for standard handguards. A smaller rectangular washer fits on the outside of the handguard and the stud is installed until it is tight. Reinstall handguard to upper receiver assembly.

 

The stud comes with a Quick Detach swivel attached. Turn the knurled section counter clockwise then push on it to release the leg on the other side so that is turns down allowing the swivel to be detached. Install the bipod onto the stud. There is a place on the bipod to install the QD swivel. After installing the swivel turn the knurled section clockwise to lock it in place.

 

The A1 and A2 birdcage flash suppressors are not long enough to bring a 14.5" barrel up to 16" legal length so the barrels that have them installed are 16" or longer so they are removable. 

 

The 14.5" barrels do have Izzy, Phantom and Phantom 2 suppressors permanently installed as they are long enough to bring the barrel up to 16" legal length. 

 

If the barrel measures 7" from the front of the front sight base to the end of the suppressor it is permanently attached. 

 

If the barrel measures 8-1/4" from the front of the front sight base to the end of the suppressor it is removable. 

 

For a list of some of our flash suppressors, please check out our online store here.

The sight base pins are tapered pins that only drive out one way. There is a small end that you need to hit to drive them out. They come out left to right (when the barrel is pointed away from you). They are very tight and need to be hit pretty hard with a large flat punch to start them. Then you use a 1/8th inch punch to drive them the rest of the way out.

Then with a wooden or plastic mallet the front sight base can be knocked free of the barrel.

Replacing the front sight with a gas block will not void your warranty but we would not warranty any issues with the new gas block unless you purchased it from us.

 

In order to remove a front sight base that is installed with taper pins you need to support the sight base on a piece of hardwood with the ejection side down. The taper pins come out left to right and are installed right to left. Break the pins free using a 1/4" diameter drift punch with a good sharp blow. A series of light hits may peen the ends over like a rivet. An 1/8" drift punch tends to skitter off the pins so you cannot get a solid hit with it. After the pins are broken free they can be drifted out with the 1/8" drift punch. Tap the sight base off the barrel with a plastic mallet.

 

Front sight bases and barrels that have the sight bases installed with taper pins are not interchangeable. Once the sight base has been installed with taper pins it is unique to that barrel. 

 

To reinstall the sight base install it onto the barrel and line up the holes as close as you can by eye. Insert the taper pins from the right side as far as you can by hand so the sight base will mount to the same position on the barrel. The pins are then set with a hammer.

 

Follow the steps below to remove the handguard from the Varminter or Predator rifle.

Note:

With all free floating handguards it is not recommended to remove the handguard for cleaning unless absolutely necessary and definitely not without the proper equipment so that it can be reinstalled correctly.  

 

If you feel it is necessary to remove the handguard for cleaning, follow the steps below to remove the handguard from the Varminter or Predator rifle.

Handguard Removal:

To remove the forward tube the upper receiver is placed in an Armorer's Action Clamp in a vise. A strap wrench is used to loosen the forward tube. It is a right hand thread so it comes off counter clockwise. After it is loose it can be unscrewed from the barrel nut. 

 

Handguard Installation:

The Varminter/Predator three piece handguard is installed by placing the upper receiver in an Armorer's Action Clamp in a vise. The barrel nut threads are lubed with Tetra Grease and the nut installed with an Armorer's Wrench to 32 to 45 ft lbs until the nut lines up with one of the holes in it and the upper receiver for the gas tube. The locking ring is turned on all the way on and the forward tube is threaded onto the barrel nut. To index the tube it is backed off to about 45 degrees from the slots and the bipod stud lining up. The locking ring is turned until it contacts the tube. A strap wrench is then used to tighten and align the tube onto the locking ring. The gas block or front sight base with gas tube is then installed.

 

Gas Block Removal and Installation:

The older Varminter/Predator gas block is held on with # 680 High Strength Sleeve and Bearing Loctite. To remove it the gas block needs to be heated with a propane torch until the Loctite softens then it can be tapped off with a plastic mallet. To reinstall the gas block all traces of the old Loctite must be removed or the new Loctite will "freeze" instantly before it can be indexed with the witness mark on the bottom of the barrel. The barrel and gas block should be cleaned with denatured alcohol before installing. Slip the gas block with gas tube installed onto the barrel. With the gas block on the barrel about 1/2" before the final position apply the Loctite around the barrel in the two places where the bands of the gas block fit. With the receiver upside down slip it in position and line up the witness mark on the bottom of the barrel to the hole in the bottom of the gas block. Wipe off excess Loctite with a patch dipped in the alcohol. Let it sit overnight to cure.

 

New Varminter/Predator barrels use a gas block held on with two set screws and no Loctite so they are easier to remove or install with a 7/64" allen wrench. To remove the forward tube the upper receiver is placed in an Armorer's Action Clamp in a vise. A strap wrench is used to loosen the forward tube. It is a right hand thread so it comes off counter clockwise. After it is loose it can be unscrewed from the barrel nut. To reinstall the forward tube the locking ring is turned on all the way to the rear of the barrel nut and the forward tube is threaded onto the barrel nut as far as it will go. To index the tube it is backed off to about 45 degrees from the slots and the bipod stud lining up. The locking ring is turned out until it contacts the tube. A strap wrench is then used to tighten and align the tube onto the locking ring.

 

Like all free floating handguards it is not recommended to remove the handguard for cleaning unless absolutely necessary and definitely not without the proper equipment so that it can be reinstalled correctly.

In order to remove the rail covers on the quad rail handguard, you want to make sure that the tabs underneath line up with the matching slots in the rail. Slide one side under the edge of the rail and apply pressure with the heel of your hand to hold the lower edge in place while pulling up the other side with your fingers to open it up starting at one end until you can press the top side onto the rail then working it on like that every 1/2" to 3/4" until you get to the other end. Start at one corner to pull back the cover working it off to the other end to remove it.

 

The Armorer's Action Block Kit wraps around the upper receiver and protects it from being crushed in the vise while you work on, or remove the barrel. The barrel vise jaw blocks are used to hold the barrel in the vise while working on the upper receiver. Only one would be used at any given time. Other necessities for this barrel removal job would be our Universal Armorers Wrench - for loosening and tightening the barrel nut and the U. S. Marine Corp. Tech. Manual.

In the simplest terms, the Bushmaster Gas Piston System cycles the rifle’s action by using gas pressure to move a Piston and an Actuating Rod. This differs from the standard AR15/M16 Type rifle (with Gas Impingement System) wherein gas pressure is routed all the way back into the Upper Receiver to act directly upon the Gas Key, Carrier and Bolt. 

 

The Bushmaster Gas Piston System Rifles and Uppers solve the common AR15/M16 Type rifle problems of excess heat buildup in the Receivers/Bolt Carrier, carbon build up, and gas leaks, by eliminating the need for Gas Tube and Gas Key of the standard system. Much like the operating systems found on AK-47 and FAL rifles, the Gas Piston System functions by tapping gas pressure off through a port in the barrel as the rifle is fired. Gas pressure pushes a Hard Chrome Plated tubular Piston (located within the Gas Block, just forward of the handguards), which drives a solid steel Operating Rod to the rear - into the Upper Receiver. There, the Operating Rod pushes a Striker Key on top of the Bolt Carrier to move the Carrier to the rear, and thereby cycles the rifle’s action. After initiating movement of the Operating Rod, excess gas pressure bleeds off through ports in the piston’s housing (the Gas Block) and exits within the Handguards to keep carbon build up and powder residue from reaching - and fouling - the interior of the Upper Receiver and Bolt Carrier. 

 

This Bushmaster Gas Piston System operates at a lower cyclic rate, functions with a wider range of ammunition, and works with less gas pressure than the standard gas impingement system rifles to improve reliability and control, as well as reduce recoil, and heat in the receivers. The detented Gas Plug at the front of the Gas Block allows easy removal for maintenance and cleaning of the system’s Hard Chrome Plated Piston. 

 

Both Complete Rifles and Barreled Upper Receiver Assemblies are available from Bushmaster. The Upper Receiver Assemblies will fit on, and work with, any military pattern 5.56mm/.223 caliber Lower Receiver. Gas Piston Uppers will function with all standard 5.56mm/.223 caliber magazines.

 

With factory ammo, the difference between a 20" barrel and a 24" barrel boils down to about 100 fps (feet per second - velocity). If you handload, you have a greater diversity of loads/powders that will function reliably. The 24" bbl. really does not give you anything extra over a 20" bbl. until you get out to about 400 yards where the extra velocity starts to make a difference. And, the longer barrels do very well with the heavier bullets (69 - 72 grain) at those ranges. If your specific interest is varmint hunting or long range target shooting, you may well benefit from a longer barrel. "DCM" Competition gets very specialized (and very long distance - up to 600 yards) - and when you get to that level, you'll probably want an extra heavy competition barrel - however, "DCM" Competition rules require the use of a 20" barrel. To accurize your DCM use rifle, we also offer 1/4 Minute of Angle Rear Sights with Micro-peeps; DCM legal trigger jobs; "free-floater" type handguard and buttstock counterbalance weights. We have all of these competition parts, so give us a call (1-800-998-7928) or see the Competition Parts Section of the Internet Catalog.

Follow these steps carefully when installing a Bushmaster two stage trigger.

Disassembly:

  1. To install the two stage trigger first remove the upper receiver from the lower receiver by pushing out the two takedown pins at the front and rear of the lower receiver. 
  2. With the lower receiver off the upper receiver the takedown pins can be pushed back in so it is easier to work on.

Hammer and Safety Selector Removal:

  1. The next step is to remove the hammer. 
  2. With the hammer in the forward position, so that it is not cocked, the hammer pivot pin is drifted out with a 1/8" drift punch and the hammer removed. 
  3. Next the trigger and disconnector are removed by drifting out the trigger pivot pin with the 1/8" drift punch and removed from the lower. 
  4. The last thing to remove is the safety selector. 
  5. This is done by unscrewing the pistol grip screw with a 3/16" allen wrench. 
  6. With the screw removed pull the pistol grip off the lower receiver being careful not to lose the safety detent spring in the pistol grip and the safety detent in the lower receiver. 
  7. If the safety detent does not come right out move the safety back and forth until the detent drops and the safety can be pulled from the receiver.

Trigger Installation:

You are now ready to install the two stage trigger components. 

  1. Install the trigger and disconnector first by placing the trigger into the lower with the trigger spring pointed forward. 
  2. Compress the trigger down until you can line up the pivot pin hole in the trigger with the hole in the receiver. 
  3. Start the trigger pivot pin into the lower and start it into one end of the trigger to hold it in place. 
  4. Insert the disconnector into the groove in the trigger and press down while inserting the 1/8" drift punch in the opposite side the pivot pin is in. 
  5. Use the 1/8" punch as a slave pin to line up the holes in the trigger and the disconnector which will hold the disconnector in place. 
  6. Tap the pivot pin in with a ball peen hammer until it captures the disconnector and remove the 1/8" slave punch. 
  7. Tap the pivot pin all the way into the receiver with the holes aligned until it is flush on both sides. 
  8. The trigger should rock back and forth freely when pulled and let go. 
  9. The disconnector should also rock back and be pushed up by its spring. 
  10. To check the disconnector push down on the rear of it with the 1/8" punch.

Safety Selector Installation:

Next the safety selector is installed. 

  1. Unscrew the tall spring plunger and set it aside. 
  2. Put the selector into the receiver and turn the receiver upside down. Install the safety detent. 
  3. Slide the pistol grip with the safety detent spring onto the receiver making sure that the spring lines up with the hole for the detent. 
  4. Reinstall the pistol grip screw. 
  5. Check that the safety moves back and forth and detents positively on safe and fire positions.

Hammer Installation:

The hammer is now installed. 

  1. Put some Neco Moly Slide lubricant into the sear notch of the hammer and just below it. 
  2. Put the hammer into the receiver so that the legs of the hammer spring are on top of the trigger pivot pin. 
  3. You can use the 1/8" punch again as a slave punch while the hammer pivot pin is installed. 
  4. Tap the pivot pin into the receiver until it is flush.

Function Check:

Do a function check of the lower receiver fire control components with the safety in the "FIRE" position. 

  1. While pulling back on the trigger, cock the hammer back with your thumb. It should click onto the disconnector. 
  2. When the trigger is released the hammer should click off the disconnector to the ready to be fired position. 
  3. Another pull of the trigger should release the hammer to the fired position. You can use your thumb to ease the hammer up so that it does not slam against the receiver. 
  4. Recock the hammer and put the safety to the "SAFE" position. 
  5. Pull on the trigger and the hammer should not fall.

Over Travel Screw Adjustment:

  1. Put the safety into the "FIRE" position and adjust the over travel screw that is still in the safety. 
  2. With the hammer cocked turn the overtravel screw in clockwise with a 1/16" allen wrench a little at a time checking to see if the hamer will fall and recocking the hammer until you get to the point where the hammer will not fall. 
  3. When you get to that point back the overtravel screw out counter clockwise until the hammer will fall. 
  4. Then back the travel screw out 1/8 turn more. 
  5. Put the safety into the "SAFE" position and tighten the locking set screw with the .035" specialty allen wrench provided with the instructions.

Spring Plunger Installation:

  1. Put the safety in the "FIRE" position to install and adjust the spring plunger that was set aside. 
  2. The spring plunger can be installed by putting the .035" allen wrench into the screw in the top and threading it into the safety or using small needle nose pliers. 
  3. Turn the spring plunger in clockwise until you can pull on the trigger and feel the trigger stop on the plunger. 
  4. You should be able to take up the slack of the first stage until that resistance is felt. 
  5. When it is felt you should be able to release the trigger and it will reset itself. If it does not reset itself turn the plunger in until it does. 
  6. Put the safety into the "SAFE" position and tighten the locking set screw with the .035" wrench.

The lower should be all set and can be reassembled to the upper receiver.
Feel free to call us at 800-883-6229 if you have any questions.

On the top and the bottom of the muzzle brake you will see little spots where the pins are welded into place that holds the brake on "permanently". With a hard drill bit and a drill press you will need to drill down through the center of these areas. Go very slowly so you don't go too far into the threads on the barrel. Then keep working the brake back and forth until the pins loosen up. Try to get the pieces of pin to fall out so they don't damage the threads while you turn it off the barrel. It's not easy but it can be done with care and patience.  If you have any concerns at all, we recommend consulting with a competent gunsmith.

To remove the pistol grip you will need a 3/16" allen wrench with a long shank. After the screw is removed the pistol grip can be pulled off of the receiver. The pistol grip has the safety detent spring in the right side that holds the safety detent in the receiver. Do not lose the safety detent or the safety will not operate properly.

      

To install a pistol grip place the safety detent spring in the hole in the right side of the grip. Be sure that the safety detent is in place. Slip the grip onto the receiver making sure the safety detent spring lines up with the hole in the receiver. Install the pistol grip screw and washer. Check the function of the safety.

Features and benefits of both stainless steel barrel and a chrome lined barrel

Stainless steel barrel:

Stainless steel is better at preventing erosion than regular 4140 steel, but we use mil. spec. 4150 ordnance steel. Then, our barrels are chrome lined and a chrome lined barrel will easily out-last a stainless barrel. A very good article on barrel manufacturing can be found in the '96 Shooter's Bible (Pg. 33). A typical stainless barrel is made from 416 stainless steel and then broach rifled. This process has been around for about 100 years. 

Chrome lined barrel:

Our chrome lined barrels are made from 4150 ordnance steel and then button rifled - a process that's been around for about 50 years. This same process has set virtually every record for the National Bench Rest Association (NBRA). Shilen, McMillan and Browning barrels all use the same process but not the same steel. Mil. spec. calls for 4150 steel - same as used in aircraft machinegun barrels and all military small arms barrels. It costs more but we think it’s well worth the price. The button rifling process work hardens the bore - making tough steel even tougher. Then, after the barrel is fully machined, it is chrome lined, making it even tougher yet - and virtually impervious to rust or erosion. This chroming process isn't like car bumper chroming. It actually welds each chromium molecule to the steel bore. This chrome lining is far more resistant to wear than a bare steel bore and it gives slightly increased velocity due to the lubricity ("slipperiness") of the chrome. And, you'll see less fouling and easier cleaning with a chrome lined barrel - all in all, a superior product.

Many people use the steel cased ammunition in our rifles with chrome lined chambers with no problems. The mild steel casings have not shown to produce any significant premature wear. For better results and reliability we recommend American factory .223 or NATO 5.56mm ammunition.

All of our barrels with chrome lining are marked B MP 5.56 NATO 1/9 or it may have HBAR for heavy barrel or 1/7 for twist. 

We do not mark our non chrome lined barrels.

The V-Match flip up sight or the folding front sight/gas block can be installed.  They can be ordered through our online store at the attached links or by calling us at 1-800-883-6229.

Yes, the flash suppressor is removable. The crush washer needs to be replaced if removed as they should not be reused.  The threads are 1/2" X 28 tpi.

Our 6 position telestock buffer tubes are commercial spec.  You can order these and other parts for your rifle on our online store at www.bushmaster.com.

 

If you install the blue follower in a 30 round .223 magazine it will hold 9 rounds of .450 ammo.

The gas piston conversion will not fit with those handguards. The ARMS SIR 50c, Daniel Defense Omega, LWRC and Troy handguards can be used.

The post ban Bullpup rifle barrel mounting system uses a barrel sleeve, split washer, locking nut and a jam nut. BATF approved the design on the threaded muzzle during the Ban as there are not enough threads to support a flash hider. If a flash hider were installed it would come off under fire.

      

The jam nut and the locking nut are the same part but have different functions. When the barrel is mounted in the receiver the barrel sleeve slides over the barrel so there is pressure between the locking nut and the receiver end cap. The sleeve is slid over the barrel then the split washer is placed on the muzzle and the locking nut is turned on until it collapses the split washer and is snug against it. A drop of # 271 Loctite is used on the locking nut. If the locking nut is tightened too much it can bend the barrel. The jam nut is then installed to keep the locking nut in the proper position. When the rifle is fired the barrel heats up so it will expand and the split washer will open up. When it cools the split washer collapses again.

      

On the pre ban rifles the barrel had longer threads on the muzzle so the flash hider was used as the jam nut against the locking nut & washer. If the locking nut is not used the flash hider could become loose. An A1 flash hider was used because it did not need to be indexed.

      

To install a flash hider on the post ban rifles the barrel sleeve must be shortened to expose more threads to support the flash hider. The barrel sleeve must be shortened from 3.6" to 3.445". A new shortened barrel sleeve is available. It is part number 30-202L-3. The locking nuts have # 271 Loctite on them so they should be heated with a propane torch to soften the Loctite for easier removal with a spanner wrench. We use the FN gas regulator tool part number MMT-0003 for. With the sleeve removed you can place it on the outside of the barrel against the end cap of the receiver. Mark and cut the sleeve so that it is just ahead of the shoulder of the barrel threads.

      

The barrel sleeve split washer and locking nut should be installed as noted above. A flash suppressor can then be installed as a jam nut. It is best to remove or install the locking nut with a spanner wrench. Use the spanner wrench to hold the locking nut in place when tightening the flash suppressor against it so that it does not move. The Loctite can be used when installing the flash suppressor as well. An A1 flash suppressor, Izzy brake or a Phantom flash suppressor is recommended as they do not need to be indexed. Adding a peel washer or crush washer to index a flash suppressor takes up threads that are needed to support the flash suppressor. If there are not enough threads to support the flash suppressor it can come off under fire.

The handle is removed by loosening the two knurled knobs on the side. Sometime you need to "help" them along with a screwdriver.

We have post ban muzzle brakes that slipover the muzzle that we pin in place with a front sight base taper pin using a high strength sleeve and bearing Loctite.

We have the Izzy, AK and Mini-Y-Comp muzzle brakes available. The Izzy muzzle brake is the most popular.

Muzzle brakes work by redirecting muzzle gases which increases noise to the shooter.

If you send us your barreled upper assembly we will install a post ban muzzle brake at no additional charge. It is the cost of the muzzle brake and return shipping. Bushmaster will only warranty factory installation of post ban muzzle brakes.

The one with the exposed firing pin is the original style semi automatic bolt carrier. The one with a shrouded firing pin is a demilled M16 bolt carrier for use in semi automatic rifles. 

Both will function equally well in semi automatic rifles.

Both springs are a little different from the mil spec springs. They have slightly different bends in them. 

We would also recommend Moly Slide paste for the sear surface of the hammer if you don't already have some. These trigger groups must be lubricated with Moly Slide to work properly. One little jar will last 3 lifetimes. You can order springs, triggers and other parts by calling us at 1-800-883-6229 and order what you need.

First check to see if the bolt carrier key screws are loose by trying to tighten them with a 9/64 allen wrench. If the key screws were loose they need to be removed so the key can be properly reinstalled.

 

To check to see if you have a leak at the bolt carrier key causing short stroking pull the bolt carrier assembly from the upper receiver. Push the bolt into the carrier and hold it there while performing this test. Spray a light oil into the key. Blow a couple of pounds of compressed air into the key. If you do not have compressed air place a rubber tube onto the key and blow into it. If there is bubbling between the key and the carrier it has a gas leak. 

 

To correct the gas leak remove one of the screws and put it back in. Remove the second screw then go back and remove the first screw. This gets the screws past the staking so that they will not be stuck in the key. Clean the key and the carrier with brake cleaner to remove any carbon build up. Put a drop of oil on the bottom of the key and wipe it off so that there is just a thin film left on it. Install the key by torquing the screws at 45 INCH pounds. The key can be restaked with a dull prick punch or cold chisel so that some of the metal of the key is pushed against the screw heads to keep them from getting loose.

You can use the bolt from your rifle with the new barrel. The barrels are pre headspaced along with the bolts that have a min/max tolerance for interchangeably while maintaining proper headspace. The bolt does not need to be "matched" to the NATO Spec chamber. The G.I. Tech Manuals warn against interchanging bolts as a rifles returned to the Armory Depot as they may have many tens of thousands of rounds fired through them and a worn bolt or barrel extension may be out of the min/max tolerances. If there is any doubt they can be checked with a NATO Spec "NO-GO" headspace gauge. If the bolt does not close on that gauge headspace is alright. Signs of excess headspace would be flattening of primers, split necks or separated cased of fired rounds.

 

We recommend replacing gas rings and extractor spring if 3,000 rounds or more have been fired with the bolt to be used to break in a new barrel.

Some States such as California, Connecticut, Massachusetts, New Jersey, New York and Puerto Rico have Laws that prohibit them from being installed. You can check with a firearms dealer in your state to see if there are any Laws that would affect you.

The compensators are blind hole drilled through the compensator into the barrel threads, the holes are pinned, the pins welded over, welds are ground flush and barrel is then sent to finish. 

 

A custom shop like this one http://www.adcofirearms.com/shopservices/ could remove it and install a new one in a different position. It would require drilling or grinding the pins out so it can be removed. 

If you notice that the primers on cases are slightly marked by the firing pin, this is a normal condition for ARl5/ M16 type weapon systems due to the lack of a firing pin spring in the design. This is part of the reason that mil. spec. parts are necessary to ensure safe operation - and we urge you to have that muzzle pointed in a safe direction when checking your rifle in this manner. MIL-R-63997B (AR) states in part (section 3.4.2) "Firing pin indent - when in a vertical (muzzle down) position, the bolt carrier assembly is released from the full recoil position and the firing mechanism is not activated, the firing pin indent shall not be more than 0.008 inch". Also, we sell a firing pin protrusion gauge that will tell you if your pin is within specifications.

Instructional information for the Red Dot Sight 1X30ST

Caution:

Before mounting your red dot sight, be sure to read carefully the operating instructions of the sight.  Be sure that your gun is not loaded and the gun's safety switch is in the "Safe" position before you attempt to install your red dot sight.  Always follow safe gun handling procedures.

  • Always keep muzzle pointed in a safe direction.
  • Gun should be unloaded when not in use.
  • Be sure of your target and what is beyond it.
  • Always wear eye and ear protection when shooting.
  • Familiarize yourself with the gun you are using.

Installing battery:

The sight uses one 3V CR2032 (or equivalent) Lithium button cell. Unscrew the battery cover, insert new battery with + side up, replace and tighten the cover. Always remember to carry a spare battery with the sight.

Mounting the sight:

1X30ST has standard 30mm main tube and can be mounted using 30mm scope rings of appropriate height and rail type depending on the desired application. The sight comes with a pair of Weaver style rings mounted. Loosen ring screws at the top and take off the bottom clamping screws. Slide the scope rings onto the mounting rail on the gun and move the sight and the rings back and forth to adjust for desired placement. Be sure to leave sufficient clearance (min. 4 inches) between your eye and the end of the sight. Rotate the sight to position the windage screw horizontally and elevation screw vertically. Tighten the ring screws, upper ones first and then the bottom ones, to securely hold the sight in place.

Zeroing, Windage and Elevation Adjustments

Caution: Since Zeroing involves actual shooting of live rounds, it should be done at an approved shooting range or equally safe area. Be sure to use eye and ear protection when shooting.

Unscrew and take off the covers of Windage/Elevation screws. Use a screw driver or coin to adjust point of impact by turning the screws in the directions as needed. Each click of the adjustment screw moves the dot by 1" at 100 yards (by 1/2" at 50 yards).

Dot Intensity Adjustment

The sight is built with a CQB reticle dot which is more visible than the conventional small dot. The brightness of the reticle dot can be adjusted by turning the battery tower which is also th ON/OFF switch. The battery tower is marked with numbers that correspond to various light intensity settings. The sight is OFF when the battery tower is set at "0" position. ALWAYS MAKE SURE THE SIGHT IS TURNED OFF WHEN FINISHED USING THE SIGHT.

Storage

When not in use, use included lens cover to protect the lens. Always keep the sight in clean and dry place. When the sight is not going to be used for a long period of time, take out the battery from battery tower. Should the lens get dusty or dirty, use soft lens cloth to wipe clean.

 

Bushmaster does not recommend installing muzzle brakes or flash hiders to our DCM/CMP or Varminter barrels with the 11 degree competition crown. There is a gap left between the muzzle and the flash hider that allows carbon build up on the crown. These carbon deposits can trap moisture causing pitting to the crown which will affect accuracy in the long run.

You may not need to worry about cleaning out the gas tube and ports unless you've been using one of the .22 rimfire adaptor kits extensively. After several thousand rounds of .22's, the gas port might have lead shavings in it, but a few .223 rounds should clean this out in good shape. Otherwise, don't worry about cleaning the gas port or tube.

If the lock nut on the buttstock will not budge at all, there may be "loctite" on the "Castle" nut. A small amount of heat may need to be carefully applied to the nut to loosen it.

THE BASIC DRILL

  1. Unload the weapon. Remove the magazine and check the chamber, and then check the chamber again. With the bolt closed, pull the charging handle to the rear and release. Place safety selector on SAFE. Pull trigger. No matter what, that hammer should not fall. If it does, that weapon is not "mission capable". Furthermore, it is just as unsafe as possible, and by no means should it be loaded until it has been serviced by a qualified professional.
  2. Place selector lever on FIRE. Pull trigger and hold to rear. The hammer should fall. While still holding trigger back, pull charging handle to the rear and release. Now release the trigger - you should hear a click as it moves forward. If no click is heard, the hammer is sticking on the disconnector and needs servicing. The hammer should not fall at this time. If it does, this is another very unsafe condition and should be checked by a qualified professional. Do not fire the weapon until it has been serviced. If you heard the trigger click as it moved forward, move on to:
  3. Pull the trigger, the hammer should fall. If you don't hear the hammer fall at this time, it fell before and the weapon needs servicing. Or, the hammer is stuck on the disconnector and the weapon needs servicing. Either way, something is very WRONG - seek out a qualified gunsmith.

THE EXTENDED LIST

At this time, we can go to the extended troubleshooting list. Remember, the steps of operation are;

  1. Firing
  2. Unlocking
  3. Extracting
  4. Ejecting
  5. Feeding
  6. Locking

We'll take them one at a time:

  1. FAILURE TO FIRE: The most probable reason for this is bad ammunition. Wait 30 seconds with the weapon pointed in a safe direction, remove the magazine, then pull the charging handle to eject the round, and examine the primer. If it has a good, deep primer strike, the ammunition is probably no good. If it has a light primer hit, it may be a hard primer, or the hammer spring may be defective or installed incorrectly, or there may be debris between the hammer and the forward wall of the lower receiver. A quick look in the lower will tell you. If it doesn't have any mark at all, the firing pin isn't reaching the round. The firing pin retaining pin may have been installed incorrectly (in front of the collar instead of behind it), the firing pin may be defective (short), or the hammer is not hitting the firing pin for some reason (not falling, hitting bolt carrier instead, debris in front, etc.). If, when trying to eject the unfired round, the charging handle is difficult to operate, the bolt may not have been locked fully forward due to an oversized round, or debris in the chamber. Riding the charging handle forward may also cause this problem. Remember, pull it back, and let go. NOTE: All AR-15 type rifles dimple the primer during feeding. This is completely normal for this type of weapon.
  2. FAILURE TO UNLOCK: Very rarely does this occur, however, it's usual cause is either a bullet stuck in the barrel behind the gas port (a squib load) or the gas tube has been installed incorrectly. If your weapon did not unlock, CHECK THE BORE FOR OBSTRUCTIONS!! Do this BEFORE you fire another round. Remove the magazine, pull the charging handle to remove the spent case, let the bolt go forward, and push out the takedown pin. Open the receivers, remove the bolt carrier, and look down the barrel. If there is no obstruction, replace the bolt carrier, close the weapon, push in the pin, and take a look at the fired case. If the case looks normal, try another round. If the same thing happens, assume it is a defective part somewhere in the gas system (probably gas tube or gas key), and have the weapon checked out by a competent gunsmith.
  3. FAILURE TO EXTRACT: This is a more common problem, usually shown by the fired case remaining in the chamber, while the carrier comes back to pick up another round, driving it into the fired case and stopping things up good. It is usually caused by a dirty chamber, a rough chamber, a weak extractor spring, a defective extractor, or bad ammo. A dirty chamber is self explanatory and only needs cleaning, while a rough chamber needs a careful polishing. Both can exhibit the same outward signs - light scratches on the fired cases, almost like a coating of frost. If the extractor is good it will usually rip a chunk out of the rim and you'll have to drive the fired case out with your cleaning rod. If the extractor is no good, then the rim will be intact - the spring is probably weak. A weak extractor spring is usually caused by overheating, another good reason to leave the bolt open after firing until the barrel can be held in your bare hand. This cools the bolt head at the same time, and keeps your extractor spring from cooking itself. The only cure is to replace the spring - a very inexpensive procedure. A bad extractor is a little more difficult to diagnose, but if you have already replaced the spring, replacing the extractor would be the next step. Bad ammo usually won't extract easily even if it is unfired, or the fired cases will show uncommon marks.
  4. FAILURE TO EJECT: This looks much the same as failure to extract, except that the fired case is removed from the chamber. The bolt will either jam the fired case back into the locking lugs on the barrel extension (crushing it), or pick up a round from the magazine and try to stuff both of them into the chamber at the same time (looks like a double-feed, except one of the cases is fired). There are a few possibilities as to the cause of this problem, and one is the ejector. For whatever reason, the ejector is weak or sticking and just not clearing the round out of the receiver. A good cleaning might solve the problem, or it may require replacing parts. Try the cleaning first. The other is that the extractor is letting go prematurely. A new extractor spring will usually solve this right away. Lastly, the bolt carrier might not be traveling back far enough, but if it is in fact picking up a new round from the magazine, this isn't the problem. If it isn't picking up a new round, you probably have a gas leak somewhere. The best thing to do is to call us. We can go over it with you in detail, on a case by case basis. Our Customer Service number is 1-800-883-6229 (Mon- Fri, 8:30 AM - 6:00 PM EST).
  5. FAILURE TO FEED: In our experience, 70% of feeding problems derive from bad magazines. Magazines have a service life just like any other part, and will wear out in time. For some reason, people never throw out their old magazines, even when they know they are no good. Some good signs of a bad mag. are: when the magazine starts to spread at the top when fully loaded; when it starts to double-feed 2 live rounds at a time into the receiver; when it fails to feed the last 2 rounds in the magazine. If you encounter any of these situations, trash that magazine. Another possible problem is an accumulation of dirt in the receiver extension, or buffer tube. Removing the buffer and spring and giving the inside of the tube a good cleaning will solve this problem. Failure to feed is not the same problem as failure to retain the magazine properly. This is either a bad magazine or a bad mag catch. Replace the offending part. Cleaning the inside of your magazines from time to time isn't a bad idea, either. If a rifle has had no cycling problem before and develops a feed problem, the cause is usually a broken or loose Bolt Carrier Key screw. Check to see if screw are tight. If a screw is broken or loose, the key must be removed. The top of the carrier and bottom of the key must be cleaned before re-installing the screw and restaking them.
  6. FAILURE TO LOCK: What usually happens here (assuming that the ammunition is not at fault) is that something prevents the bolt carrier from moving fully forward. AR-15 type rifles have a safety notch cut into the top of the hammer which engages the collar of the firing pin to prevent slam firing in the event of disconnector failure. A faulty "trigger job" can lead to this condition, as can an out of tolerance receiver, or a missing or stuck disconnector or disconnector spring. This condition will exhibit itself even when the weapon isn't being fired. Another problem that can cause much the same symptoms is a damaged gas key or gas tube. If the carrier cycles fine when not being fired, but jams when being fired, you can be pretty sure the problem is either in the bolt or the chamber. An ejector that protrudes beyond the front surface of the bolt will usually create an intermittent jam that can drive you nuts, and requires replacing the ejector. An extractor whose slot is not level with, or slightly below the bolt surface may cause the same problem. If the weapon has the same problem even when using a bolt of known reliability, then you can be sure that the problem is in the barrel somewhere. Remember that a failure to lock will also cause a failure to fire, so check things over carefully before ejecting the unfired round.

A SPECIAL NOTE: Lately we have been noticing that primers have been blowing out of their pockets at a much higher rate than usual. This seems to be a result of a diminished primer crimp applied to most .223 or 5.56 ammo by the manufacturer (probably to ease reloading). These loose primers can wreak havoc inside the receivers, causing all manner of binding, jams, and general mayhem. If you've got a jam that's driving you crazy, one that comes and goes, this might be the cause. A small rifle primer is just the right size to drop down inside the pistol grip screw hole and hide until the vibration of firing shakes it out, jamming the trigger but good. Compressed air will usually get these little suckers out, but sometimes you'll have to pull your hammer and trigger to get at it. It's something to watch for, anyway.

Yes, it's normal for an AR type rifle to have a heavier trigger pull in comparison with to a bolt action rifle. The milspec(MIL-R-63997B(AR)) lists an acceptable trigger pull as being between 5.5 and 9.5 pounds (section 3.4.3). Our two-stage competition triggers come in at 4.5 pounds total.

Since there is a complete powder burn in the 16" barrel there is very little, about 60 FPS, difference in velocities.

M16 fire control parts (hammer, trigger, disconnector & safety selector) and the auto sear. Some companies are shipping rifles with M16 bolt carriers. Bushmaster supplies demilled M16 bolt carriers that cannot trip an auto sear.

Bushmaster marks the chrome lined barrels with B MP 5.56 NATO 1/9 or 1/7 and HBAR if it is a heavy barrel. The 6 position telestocks have the Bushmaster snake logo. Upper receivers may have a "L", "O", "Y" or inverted "T" stamped onto the rear of the upper receiver takedown lug but some are not marked. The inside of the upper receivers is a lighter gray color than the outside as a Mil Spec dry film lube is baked onto the inside which many other manufacturers do not include. Bushmaster uses an allen head cap screw that uses a 3/16" allen wrench for the pistol grip screw. Steel parts are manganese phosphate finished and aluminum parts are hard coat anodized. The barrels have forged front sight bases installed with taper pins and not castings. Polymer handguards have heat shields installed.

There can be a number of reasons that cause a gun to jam.  

Look carefully at the problem area:

Many times we get calls where the person can't describe exactly what the problem is. This makes phone diagnosis very difficult. The best thing to do when you get a jam is to really look things over well - even make notes as to what you see.

Be Careful-Especially with Jams Involving Live Ammunition!

Keep the rifle pointed in a safe direction, until you figure out what has happened. 

As you inspect your rifle, ask yourself these questions...

Look at the bolt carrier through the ejection port. 

  • Is it fully forward? 
  • Is this a failure to fire or a failure to feed? 
  • Is there a round in the chamber? If so, keep the rifle pointed in a SAFE DIRECTION. 
  • Is it a fired case? 
  • Is this a failure to eject?
  • Did the hammer actually fall? 

Here are a few hints as to what the trouble MIGHT be:

The rifle has jammed and...

  • Bolt is Stuck Halfway - Two Rounds in Front, One Spent, One Live. 
    • Probable Cause: Extractor or Spring. 
  • Bolt is Stuck Halfway - One Spent Round in Front, Crushed. 
    • Probable Cause: Ejector or Spring. 
  • Bolt is Stuck Halfway - No Rounds Present. 
    • Probable Cause: Hammer or Firing Pin (Occurs usually when cycling action by hand). 
  • Bolt is Stuck Halfway - Live Round in Chamber!!! 
    • Probable Cause: Disconnector Failure. 
  • Bolt is Closed - Louder than Normal Firing Noise, Unable to Pull Bolt Back. 
    • Probable Cause: Case Head Failure. 
  • Bolt is Closed - Hammer Won't Fall. 
    • Probable Cause: Disconnector/ Hammer problem. 
  • Bolt is Closed - Hammer Won't Fall. 
    • Probable Cause: Debris Between Trigger and Safety. 
  • Bolt is Closed - No Round in Chamber. 
    • Probable Cause: Gas Ring Gaps Aren't Staggered. 
  • Bolt is Closed - No Round in Chamber. 
    • Probable Cause: Magazine Failure. 
  • Bolt is Closed - No Round in Chamber. 
    • Probable Cause: Broken or Loose Gas Key Screw. 

 

This is not a complete list, but if you haven't found the solution to your problem here, please call us. We'll be glad to help you sort it out.
 

The best way to avoid malfunctions (jams):

1. Use good quality ammunition from a reliable manufacturer.
2. Clean your weapon frequently and lubricate it properly (don't over-lubricate!).
3. Practice, practice, practice. Most malfunctions occur during the initial break-in period.

Solutions to what may cause an M4 A3 to short stroke.  (After the last round the bolt will not stay back or will get stuck almost half way.)

Solution

We usually recommend replacing gas rings about every 3,000 rounds or so for reliable functioning. Our new gas rings  have an angled gap now so if you reverse the center ring there is no gap even if they line up. 

 

You could check to see if there is a gas leak at the bolt carrier key;

 

Subject: Bolt Carrier Key, leak

The key is the piece on top of the bolt carrier held in place with two screws.

First check to see if the bolt carrier key screws are loose by trying to tighten them with a 9/64 or 1/8" allen wrench depending on the screws used. If the key screws were loose they need to be removed so the key can be properly reinstalled.

To check to see if you have a leak at the bolt carrier key causing short stroking pull the bolt carrier assembly from the upper receiver. Push the bolt into the carrier and hold it there while performing this test. Spray a light oil into the key. Blow a couple of pounds of compressed air into the key. If you do not have compressed air place a rubber tube onto the key and blow into it. If there is bubbling between the key and the carrier it has a gas leak.

To correct the gas leak remove one of the screws and put it back in. Remove the second screw then go back and remove the first screw. This gets the screws past the staking so that they will not be stuck in the key. Clean the key and the carrier with brake cleaner to remove any carbon build up. Put a drop of oil on the bottom of the key and wipe it off so that there is just a thin film left on it. Install the key by torquing the screws at 45 INCH pounds. The key can be restaked with a dull prick punch or cold chisel so that some of the metal of the key is pushed against the screw heads to keep them from getting loose. A drop of Loctite can be used on the screw threads instead of staking the heads.

The correct mil. spec. cleaner/lubricant for AR15/M16 rifles is "Break Free" with CLP. However, we realize many people use other solvents, and we sell a comparable product from Tetra. The ammonia in Sweet's will not harm the chrome lining of the barrel, but long exposure may damage the receiver's finish. The use of a chamber rod guide should keep the solvent off the receivers, if you remove the lower when cleaning.

We install the bipod stud by drilling and tapping the aluminum handguard for it. 

  • Locate the position you want the stud, usually half way between the end and the knurling, then use a prick punch to mark it so the drill will not walk. 
  • A top dead center punch works best with the receiver upside-down and receiver leveled. 
  • Use a # 21 drill bit for the hole. 
  • Then tap the hole with a 10-32 tap. 
  • Install the stud with a drop of # 271 Loctite on the threads.
  •  

The 1/9 twist barrel will stabilize bullets from 40 to 75 grains. There is no "best" bullet, brand or weight as each barrel has its own harmonics so we do recommend trying a variety to see what works best in your rifle. The Black Hills ammunition in a variety of weights usually performs very well. Others to try would be the Winchester 45 grain Varminter, Federal Gold 69 grain BTHP and Hornady 75 grain TAP ammo.

If the barrel is 16" or longer the flash suppressor can be unscrewed and replaced. It is recommended that you use a set of barrel vise jaw blocks when removing or installing flash suppressors.

A replacement crush washer should also be used.

 

If the barrel is less than 16" long the suppressor has been permanently attached to bring the barrel up to 16" legal length. Bushmaster is not set up to do individual piecework on barrels such as replacing permanently attached flash suppressors. 

Cleaning your AR is an essential step in maintaining your AR.  Follow these procedures to keep your firearm in proper working order.

 

Cleaning the AR15 - with its chrome lined barrel - is a little different than cleaning a regular sporting rifle. The chrome lining will take longer to break in - usually 100 - 200 rounds, and once properly broken in, will really not require much scrubbing until many thousand rounds later when your target groupings start to suffer. Chrome barrels don't get fouled nearly as quickly as steel barrels, and they won't rust or pit either. 

 

Here is the basic cleaning process - after a shooting session, clean the bore and chamber with a nitro solvent (Hoppe's or equivalent) and run patches through until all solvent is removed. Caution - any solvents that can affect nickel may damage the finish of the receiver unless removed. A Nickel Acetate sealant is applied as one of the receiver's last finishing steps, and some solvents will attack that finish. 

 

The use of a chamber rod guide (available in our catalog) will limit your cleanup. Once the rifle is clean and dry, apply a light oil with Teflon but don't over-do it. We sell the Tetra brand, others are Break-Free and Rem-Oil. The manual that comes with your rifle will show you how and where to oil. After many (thousands) of rounds, if the rifle's accuracy starts to suffer, scrubbing the bore down with a good copper solvent, plenty of elbow grease, and patience, will produce a barrel that shoots as good as new.

The FP-10 CLP or similar CLP product will work well.

Temperature should not exceed 325 degrees F.

What works for us is using a large flat blade screwdriver that we have ground the sides down to fit inside the charging handle slot of the upper receiver. Slide it into the receiver with the receiver upside down to lift up on the gas tube if needed. We also use it by inserting it from the top to pry the gas tube to the center. Remove the bolt from the carrier to check the gas tube/key fit by sliding the stripped bolt carrier into the receiver. If it’s the gas tube note which way it is deflected so that it can be adjusted until there is no resistance felt when the stripped bolt carrier is installed.

We suggest Tetra Gun Blue for the steel parts as it turns the metal black and blends well with the finish.

For aluminum parts the Birchwood Casey liquid aluminum black # 15125 for around $9.00 can be used for the aluminum parts.

We get our front sight base forgings from a couple of different vendors and these are their markings. They don't have any meaning other than this.

With a single stage trigger you squeeze the trigger until the hammer is released to take a shot. You do not know exactly when the trigger will break releasing the hammer for the shot. There is also some additional overtravel of the trigger after the shot is fired that may throw off sighting a bit for a follow up shot.

 

With a two stage trigger you have a take up the trigger until a slight resistance is felt, which is the second stage. It takes an additional pound of pressure to overcome the second stage so you will know precisely when the shot will be let off. If you do not take the shot when you release the trigger it will reset itself. It also has an overtravel adjustment to limit trigger travel once it has been fired which helps to keep on target. You can also pull straight through the second stage when rapid firing.

The standard version is for a standard barrel diameter of .610". The Heavy version is for the heavy barrel diameter of .720". If you have a 16" with a heavy barrel you will need the heavy barrel version. Other than that they both have the same look and basically give the illusion that the gun has a short barrel with a long flash hider.

Most modern barrel steels are a ChroMoly Vanadium steel alloy that contains elements such as chromium, nickel, molybdenum etc for strength and hardness properties and are not as prone to oxidation or rusting as milder steel alloys. Milder steel alloys can rust within a matter of minutes or hours while the harder steel alloys will take longer but as long as proper maintenance is done such as cleaning and oiling the barrels they can last many years without any signs of rusting. If not properly maintained they can have rusting occur which causes pitting in the steel.

The differences between the A2 and A3 sights are that the A2 sight is installed directly into the receiver with fixed carry handle while the A3 sights are a part of a detachable handle used on the flat top receivers with Picatinny rail. The sight base in the detachable A3 handle is shorter. The A2 sight is adjustable for 1 MOA elevation and 1/2 MOA windage. MOA ( minute of angle ) is 1" at 100 yards. The A2 elevation adjustment is good for out to 800 meters with an 8/3 index. The A3 sight is adjustable for 1/2 MOA elevation and windage with the elevation adjustment out to 600 meters with the 6/3 index.

 

Since the A3 handle is 1/2 MOA elevation adjustment you need to click up 2 clicks instead of 1 to the "Z" mark to set for 25 meter battlefield zero.

 

Only the A3 models have removable carry handles on the flat top receivers with Picatinny rail. 

 

All Bushmaster 5.56/.223 barrels are chambered in 5.56mm so both 5.56mm and .223 ammunition can safely be used. SAAMI does not recommend firing 5.56 ammunition in rifles chambered in .223 as the shorter throats will cause higher than normal pressures.  

The forward assist is used per the operating manual to insure that the first round loaded has been completely chambered. It was added during the Vietnam era when poor cleaning practices and ammunition that was very dirty could cause chambering problems. The forward assist is seldom if ever needed now with the improvements in materials and ammunition. 

It is not meant to force a bent or damaged cartridge into the chamber that could develop excessive pressures. 

You can safely and accurately fire up to a 75 grain bullet in the Bushmaster chrome lined 1 in 9" twist barrel - even an 80 grain can be fired safely but accuracy will suffer.

After firing a couple hundred rounds, the chrome lining will "polish out" from its light, flat gray, factory-new look to a brightly reflective, polished appearance. During this break-in period, excessive cleaning with solvent or brush should be avoided as that will only prolong the time (and number of rounds) it takes to achieve the final "bullet polishing" of the barrel.

It is the same thread used on the .308 rifles which is 5/8" X 24 TPI.

You can use nylon and bronze bore brushes as they will not harm the hard chrome lined barrels.

You can use nylon and bronze bore brushes as they will not harm the hard chrome lined barrels.  You can purchase brushes and other cleaning products through our online store at www.bushmaster.com or by calling us at 1-800-883-6229 Mon. through Fri. 9:00 am - 5:00 pm EST.

 

If properly operated and maintained, the average shooter will not have to replace any parts on his/her AR15 in their lifetime. There are some wear items - the gas rings, the extractor spring, the extractor, the disconnector, the hammer pin - that may eventually wear out and overheating the weapon is usually the culprit. If the barrel is heated up, cool it down with the bolt open. Lock the bolt back and leave the ejection port cover open.

Placing the weapon in a vertical position helps, too and let it cool until you hold, not just touch, the barrel with your bare hand. This prevents the heat from damaging the parts listed above. Many AR15 parts are damaged - or lost - by people trying to work on their rifles without benefit of the information in the Tech. Manual. For the cost of the user manual, it can save you many more dollars by showing you how to do it right. For problems in the field or on the range, we offer our Emergency Repair Kit which includes: extractor; 2 extractor springs; 2 extractor spring inserts; disconnector. gas ring set; extractor pivot pin; firing pin; 2 firing pin retaining pins; cam pin and spring package of 6 springs.

We would recommend a flat black Birchwood Super Black touch up pen for scratches on the M4-type A3 carbine receiver, picatinny rail, etc.

Follow the steps below for removal and installation of the front sight housing.

How to remove:

  • In order to remove a front sight base that is installed with taper pins you need to support the sight base on a piece of hardwood with the ejection side down. 
  • The taper pins come out left to right and are installed right to left. 
  • Break the pins free using a 1/4" diameter drift punch with a good sharp blow. 
    • A series of light hits may peen the ends over like a rivet. 
    • An 1/8" drift punch tends to skitter off the pins so you cannot get a solid hit with it. 
  • After the pins are broken free they can be drifted out with the 1/8" drift punch. 
  • Tap the sight base off the barrel with a plastic mallet.

      

NOTE: Front sight bases and barrels that have the sight bases installed with taper pins are not interchangeable. Once the sight base has been installed with taper pins it is unique to that barrel. 

How to reinstall:

  • To reinstall the sight base install it onto the barrel and line up the holes as close as you can by eye. 
  • Insert the taper pins from the right side as far as you can by hand so the sight base will mount to the same position on the barrel. 
  • The pins are then set with a hammer.

In order to remove a front sight base that is installed with taper pins you need to support the sight base on a piece of hardwood with the ejection side down. The taper pins come out left to right and are installed right to left. Break the pins free using a 1/4" diameter drift punch with a good sharp blow. A series of light hits may peen the ends over like a rivet. An 1/8" drift punch tends to skitter off the pins so you can not get a solid hit with it. After the pins are broken free they can be drifted out with the 1/8" drift punch. Tap the sight base off the barrel with a plastic mallet.

 

Front sight bases and barrels that have the sight bases installed with taper pins are not interchangeable. Once the sight base has been installed with taper pins it is unique to that barrel. 

 

To reinstall the sight base install it onto the barrel and line up the holes as close as you can by eye. Insert the taper pins from the right side as far as you can by hand so the sight base will mount to the same position on the barrel. The pins are then set with a hammer.

To remove the forward tube the upper receiver is placed in an Armorer's Action Clamp in a vise. A strap wrench is used to loosen the forward tube. It is a right hand thread so it comes off counter clockwise. After it is loose it can be unscrewed from the barrel nut. To reinstall the forward tube the locking ring is turned on all the way to the rear of the barrel nut and the forward tube is threaded onto the barrel nut as far as it will go. To index the tube it is backed off to about 45 degrees from the slots and the bipod stud lining up. The locking ring is turned out until it contacts the tube. A strap wrench is then used to tighten and align the tube onto the locking ring.

      

Like all free floating handguards it is not recommended to remove the handguard for cleaning unless absolutely necessary and definitely not without the proper equipment so that it can be reinstalled correctly.

We offer sight tools and other gunsmithing tools through our online store here. Click on the Options menu then highlight A2 rifles then click on Update and part number RAY-005 sight tool for A2 sight post will be ordered.

The NECO Moly-Slide a molybdenum disulfide paste is recommended for the barrel nut. We also use it for the sear surfaces of our competition triggers. Item # F1001639. It can be purchased through our online store or by contacting consumer services direct at 800-883-6229.

The chrome-moly fluted barrel is manufactured to tighter tolerances for better accuracy than the stainless steel barrels.

Our chrome lined barrels and stainless barrels have bores that are 1/2 the Mil-Spec tolerances with 5.56mm NATO Spec chambers and step crowns. 

The non chrome lined 24" fluted 1 X 9 Varminter barrels have bores that can be held to 1/2 the tolerances again with a tighter SAAMI Spec headspaced chamber with the longer NATO throat that will accept 5.56mm ammunition and an eleven degree competition crown. They are manufactured to the same specs as our 20" 1 X 8 DCM barrels except for twist rate. The 20" Predator barrel is a fluted DCM barrel. The 20" DCM, 20" Predator and 24" Fluted Varminter barrels are the most accurate barrels that we produce.

The .450 will work with the collapsible stock but we would recommend using the heavy M4 buffer or a hydraulic carbine buffer  for the recoil.

The 6.8 SPC upper will fit and function on the 5.56 lower receiver with no modifications.

Yes our 6.8 upper should fit on an S&W M&P lower.

Our upper will match with old or new Colt lowers, however, Colt made many interim models with a large (larger than mil. spec.) pivot pin. If your front receiver pin is larger than the rear takedown pin, you have one of these Colt models. This causes no problems as we sell an adapter pin that will fit your lower to any of our uppers - or vise versa. This will require the use of an Offset Pin to adopt your Colt lower receiver to M16 forward assist type upper receiver with the smaller hole. You may wish to contact companies such as Brownell’s or Midway USA for this offset pin. 

These were discontinued (F1001670 ) and are no longer offered.

 

A DPMS 7.62 X 39 upper will fit on the Bushmaster lower receiver. 

Different caliber AR-15 compensators use different thread sizes. The .223/5.56 compensators are 1/2" X 28 tpi. The 7.62/.308/6.8 SPC compensators are 5/8" X 24 tpi. The 9mm compensators are 1/2" X 36 tpi.

The gas piston retro kit will fit and function with the 6.8 SPC carbine upper.

The PRS buttstock will fit your .450 rifle with no modifications. The stock comes with installation instructions.

You can special order a 6.8 SPC gas piston system upper or have your FFL firearms dealer a complete 6.8 SPC carbine. It is best to call our Parts Department at 1-800-998-7928 for ordering and pricing.

 

Help

Rebate Forms and Helpful Hints

Bushmaster rebate forms can be filled out online.  Once you fill it out, print it and mail all required documentation to the address listed on the rebate form.

If you simply wish to download the form and fill it out manually, you can download the rebate form 

We recommend that you maintain a photocopy for your personal records of the information you are mailing.

 

It is extremely important to read and complete all the steps of the rebate.  If any are incomplete or missing documentation, the rebate could be denied.

 

One of the biggest reasons for rebates being denied or delayed is due to incomplete documentation. 

  • The original cash register receipt(s) MUST be included for each applicable rebate.
  • The original proof of purchase sticker(s) from your box must also be included.  
    • On Bushmaster firearms, this sticker could be INSIDE the box. 
    • Proof of Purchase sticker can be identified by a bar code and will state "proof of purchase" above the code and serial number below the code. See example below:

 

Send the Proof of Purchase Sticker:

        

 

 

Do not send either of these:

          

 

 

Also, be sure to review the purchase date range, postmark date, and particular models that the rebate is offered for.

Rebate Status

It does take some time to process rebates at our fulfillment center.  We ask that you please allow 10-12 weeks for processing.

If it has been 10-12 weeks and you still have not received your rebate, we offer a number of ways to check the status. 

You can go online and fill in your contact information or tracking id through our online tracker 

If you have questions or would like to speak to a representative about your rebate, please call our rebate center at 1-800-953-3098.

 

We have seen this happen many times here. We get rifles all the time for warranty service that have our lower receiver, but every other part is a gun show special. Before purchasing, look things over carefully. You are about to lay down a sizeable chunk of money, so take a minute to be sure of what you are buying. Bushmaster's identifying marks are: 

  1. On the barrel, in front of the front sight, it will be stamped: "B MP 5.56 NATO 1/9 H BAR" (exactly that way). On some barrels, it may be under the handguard, but it will still say that exact thing. The only difference might be a 1/7 instead of a 1/9 . This denotes the rifling twist. 
  2. Our front sights are held on by two taper pins, one through each of the bands of the front sight. We do not use hollow roll pins, never have - never will. 
  3. Our handguards have aluminum heat shields in them. 
  4. Our barrels have the correct gray/green manganese phosphate finish, not black. 
  5. Our tele-stocks have a small roll pin holding the nut on under the sliding latch. If it's not pinned, it's not ours. 
  6. Our hammers and triggers have polished contact surfaces. 
  7. We always use aluminum delta rings to retain the handguards. 
  8. Our buffers have a gold-colored finish on them, which is easy to see inside the stock. 
  9. Our aluminum parts all have the mil. spec hard anodized flat or matte finish to them, not shiny. This includes the receivers, the charging handle, and the delta ring. However, oil on the surface might make the normally flat or matte finish appear shiny. The best insurance is to always buy from a local dealer, someone you can go back to if you have any problems. Most of them are reputable, and will at least help you contact the factory for service problems.

For your convenience we offer digital versions of our catalogs and manuals that you can download for free. 
Beginning in 2015 our catalog is now exclusively in digital version through our website at www.bushmaster.com or by clicking the following link: Bushmaster Catalog.