Bushmaster Firearms

FAQ ID # 1819
Last Update : 2009/09/11
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Question / Issue
I have a Bushmaster varminter and I want to replace the gas block but the original does not have the tapered pins to hold it in place. How is it removed? Thanks

Answer / Solution
They are removed and installed the same way as the DCM/CMP sights. Newer models also have 7/64" set screws.
 Subject: DCM/CMP front sight base installation
 
       DCM/CMP front sight bases are installed with # 680 green High Strength Sleeve and Bearing Loctite. This eliminates the use of taper pins which could exert tension on the barrel when heating up during firing affecting accuracy. The high strength of this product will not allow the sight base move even when the barrel gets hot.
      In order to remove the sight base it needs to be heated with a propane torch to soften the Loctite. Remove the set screws and continue to heat the bands of the sight base moving the torch constantly so the finish is not damaged. It will need to get very hot to soften the Loctite but not so hot it would change the color of the metal. It then requires a plastic mallet to smartly strike the sight base and remove it from the barrel.
      Before reinstalling the sight base all traces of the old Loctite must be removed or when in comes into contact with the new Loc-tite it will instantly freeze it in place. This does not allow enough time to check and set the sight base for proper alignment for windage.
 
      The sight base is installed after the free float handguard is installed. When installing the sight base to the barrel the parts must be cleaned with denatured alcohol. Slide the sight base onto the barrel about 1/2" before it contacts the shoulder. Place two beads of the # 680 Loctite around the barrel where the sight base bands will be located. Push the sight base all the way up to the shoulder of the barrel while rotating the sight base back and forth to distribute the Loctite between the barrel and sight base. Wipe off excess Loctite with a cleaning patch and denatured alcohol. Align the sights by bore sighting the upper or using a laser boresighter. Install the set screws with # 271 Loctite. On a stable platform let the Loctite set up for 10 to 15 minutes. Wait 24 hours for the Loctite to completely cure before firing the rifle.
     
 There should be a witness mark located in the center of the bottom hole in the gas block to tell if it is centered over the gas port. 


Direct Link to This FAQ
http://www.bushmaster.com/faqs/?f=1819

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