AR15 gas block installation...please help.

Discussion in 'Gunsmithing Forum' started by kcobean, Aug 6, 2012.

  1. kcobean

    kcobean New Member

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    I have a barrel from an old Bushmaster that I want to put a low-profile gas block on so I can install a quad-rail. I got the original FSB off but for the life of me I can't get the new gas block on. It gets stuck HARD at the area where the FSB used to sit. I just can't get it all the way onto the barrel. Do I need to freeze the barrel and heat the gas block or something?



    The new gas block is held in place with allen screws rather than the pins the old one was held in with. I'm assuming this thing is machined with tolerances intended to keep it in place with just some loctited screws (IOW, it's tight as hell!)

    Anyone have any tips?

    Thank you very much.
     
  2. 454fan

    454fan New Member

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    take a allen that will just spread the slot and hopefully it will slide on
    I just installed a piston conversion and had the same problem you are having and spreading the gap a little made it easier
     

  3. kcobean

    kcobean New Member

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    Thanks 454fan. There is no slot on this gas block, The allen screws don't clamp the block together, they screw in to the barrel. I took a micrometer to the barrel and it's .750 exactly as it should be. The inside of the gas block however is .734 or so. I'm gonna have to use some sandpaper or something and hone it out a bit. For now, I found a different gas block that will work.

    Thanks again.
     
  4. JonM

    JonM Moderator

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    i would send the block back its out of spec. while some parts can require fitting .016 is much more material than a simple lapping can remove. sounds like the reamer that was used to make that block was past the end of its life span.
     
  5. kcobean

    kcobean New Member

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    Thanks John. I was wondering if that might be the case. I'll return it or exchange it.