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Thread: Secure your gas block, please...

  1. #1
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    Secure your gas block, please...

    This is a PSA: Ensure your gas block is properly secured! This means, either pinned, or a dimple for a set screw plus thread locker.

    I was able to attend a carbine class this past weekend (thank you Jim Carter, et al) and there were two gun problems. One was a low-pro gas block that worked forward enough to make the gun a single-shot. This was near the end of day one, and after several thousand rounds through the gun prior to this class. This gun was purchased fully assembled, not home-grown. (Not that home-built is bad; just FYI)
    There was no pin and no set screw dimple. In this case, it was a minor inconvenience because we were on the range. A backup gun allowed the shooter to keep learning, and we fixed the problem that night.
    It got several other shooters wondering about their gas block situation. After a quick look at three guns, we found two others in the same condition (no pin/dimple. Neither GB had moved.)

    So, how reliable does your rifle/carbine need to be? Just sayin'...
    Last edited by MQ105; 03-07-18 at 10:13.

  2. #2
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    I can't understand the concept of just relying on a dimple and some LocTite for a weapon that ostensibly needs to be maximally reliable. Especially when pinning the gas block is so cheap. I've seen enough dimpled gas blocks shoot loose in high round-count carbine courses that I just roll my eyes when I see folks on this forum note that a dimpled gas block is "good enough".

  3. #3
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    From what I remember when I first joined M4C in 2006, it was pinned GB and thats it!

    And then BCM came along without pins and made it work. Not sure if the dimple wasn't a thing in 2006 but here we are with lots of BCMs on the street without issues. My few BCM uppers with low pros were 100% and I was confident in them.

    For my last build, it was a set screw block, with a dimple, and pinned by ADCO. Belts and suspenders!

  4. #4
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    I used to be of the mind that the only acceptable method was to pin a GB. However, I now believe that a properly dimpled barrel with a thread-locked set screw is good, assuming the hand guard covers the GB.

  5. #5
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    Wow. First time I've heard of this happening. Thanks for sharing.
    "You people have too much time on your hands." - scottryan

  6. #6
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  7. #7
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    Quote Originally Posted by Hmac View Post
    I can't understand the concept of just relying on a dimple and some LocTite for a weapon that ostensibly needs to be maximally reliable. Especially when pinning the gas block is so cheap. I've seen enough dimpled gas blocks shoot loose in high round-count carbine courses that I just roll my eyes when I see folks on this forum note that a dimpled gas block is "good enough".
    What would constitute as high round count? This is the first time I've heard of this being a common issue.

    I physically shot out a BCM barrel without a pinned block and never had a problem. No one I used to shoot with (guys in a unit that people pay $250/day to go to Gun Camp with) had issues with the non-pinned blocks on their personal rifles, either.

  8. #8
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    Secure your gas block, please...

    Quote Originally Posted by Hmac View Post
    I can't understand the concept of just relying on a dimple and some LocTite for a weapon that ostensibly needs to be maximally reliable. Especially when pinning the gas block is so cheap. I've seen enough dimpled gas blocks shoot loose in high round-count carbine courses that I just roll my eyes when I see folks on this forum note that a dimpled gas block is "good enough".
    Were they assembled by autisms?

    Also can you quantity “seen enough”?


    Sent from my iPhone using Tapatalk
    Last edited by jpmuscle; 03-07-18 at 10:57.
    “Answer The Bell...” J.W.

  9. #9
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    Green loctite.

    You're welcome.

  10. #10
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    The dimple is for alignment of the GB.

    Quote Originally Posted by Hmac View Post
    I can't understand the concept of just relying on a dimple and some LocTite for a weapon that ostensibly needs to be maximally reliable. Especially when pinning the gas block is so cheap. I've seen enough dimpled gas blocks shoot loose in high round-count carbine courses that I just roll my eyes when I see folks on this forum note that a dimpled gas block is "good enough".

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