Bushmaster Firearms

FAQ ID # 30
Last Update : 2008/04/13
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Question / Issue
How to install our Bushmaster Two Stage Trigger?

Answer / Solution

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. With the lower receiver off the upper receiver the takedown pins can be pushed back in so it is easier to work on.

The next step is to remove the hammer. 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. 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. The last thing to remove is the safety selector. This is done by unscrewing the pistol grip screw with a 3/16" allen wrench. 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. 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.

You are now ready to install the two stage trigger components. Install the trigger and disconnector first by placing the trigger into the lower with the trigger spring pointed forward. Compress the trigger down until you can line up the pivot pin hole in the trigger with the hole in the receiver. Start the trigger pivot pin into the lower and start it into one end of the trigger to hold it in place. 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. 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. Tap the pivot pin in with a ball peen hammer until it captures the disconnector and remove the 1/8" slave punch. Tap the pivot pin all the way into the receiver with the holes aligned until it is flush on both sides. The trigger should rock back and forth freely when pulled and let go. The disconnector should also rock back and be pushed up by its spring. To check the disconnector push down on the rear of it with the 1/8" punch.

Next the safety selector is installed. Unscrew the tall spring plunger and set it aside. Put the selector into the receiver and turn the receiver upside down. Install the safety detent. 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. Reinstall the pistol grip screw. Check that the safety moves back and forth and detents positively on safe and fire positions.

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

Do a function check of the lower receiver fire control components with the safety in the "FIRE" position. While pulling back on the trigger, cock the hammer back with your thumb. It should click onto the disconnector. When the trigger is released the hammer should click off the disconnector to the ready to be fired position. 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. Recock the hammer and put the safety to the "SAFE" position. Pull on the trigger and the hammer should not fall.

Put the safety into the "FIRE" position and adjust the over travel screw that is still in the safety. 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. When you get to that point back the overtravel screw out counter clockwise until the hammer will fall. Then back the travel screw out 1/8 turn more. Put the safety into the "SAFE" position and tighten the locking set screw with the .035" specialty allen wrench provided with the instructions.

Put the safety in the "FIRE" position to install and adjust the spring plunger that was set aside. 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. Turn the spring plunger in clockwise until you can pull on the trigger and feel the trigger stop on the plunger. You should be able to take up the slack of the first stage until that resistance is felt. 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. 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 if you have any questions.

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