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Thread: How important is a pinned-on gas block?

  1. #11
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    Quote Originally Posted by Todd.K View Post
    There is your clue...
    Yep.
    Chief Armorer for Elite Shooting Sports in Manassas VA
    Chief Armorer for Corp Arms (FFL 07-08/SOT 02)

  2. #12
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    Is the potential danger exclusively impact damage, or are there any other possible problems with non-pinned GBs?

    Am I correct in assuming that non-pinned GBs that are covered by a FF rail are more robust, or should they be pinned as well?

  3. #13
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    I think the biggest threat for a non pinned front sight is a sharp impact.

    The gas block under a rail will not see the impact. The second problem is heat cycles, this can brake down thread locker and loosen fasteners. The clamp style with staking of the screws is my choice if I had to.

    The cost of getting the gas block pinned is small compared to the peace of mind.

  4. #14
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    Quote Originally Posted by gotm4 View Post
    Mk12s used to have set screwed gas blocks. Now they're pinned.
    Yes. Those were of the set-crew variety. As my gunsmith explained, those are the least secure option, as the contact surfaces where locking force is exerted is quite small, at the 12 o'clock position where the block is being drawn down, and of course where the set screws are being forced up. The bolt-on variety is a different story, with a much broader contact area; again, he pointed out this feature on his motorcycles.
    "The secret to happiness is freedom, and the secret to freedom is courage." - Thucydides, c. 410 BC

  5. #15
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    Quote Originally Posted by wild_wild_wes View Post
    Yes. Those were of the set-crew variety. As my gunsmith explained, those are the least secure option, as the contact surfaces where locking force is exerted is quite small, at the 12 o'clock position where the block is being drawn down, and of course where the set screws are being forced up. The bolt-on variety is a different story, with a much broader contact area; again, he pointed out this feature on his motorcycles.
    What kind of operating temps did your gunsmith find at the gas block at the barrel? If so how did it compare to that of the motorcycle forks?
    Last edited by Robb Jensen; 12-14-09 at 22:43.
    Chief Armorer for Elite Shooting Sports in Manassas VA
    Chief Armorer for Corp Arms (FFL 07-08/SOT 02)

  6. #16
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    I would not own an AR that did not have a Pinned gas block.

    It's the key to the whole system, and if it becomes misaligned just once....it's a single shot... don't care how it's made, set screws can shear or crack... you do want you want.

  7. #17
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    if you're using a lo pro gas block i always recommend getting a dimpling the barrel for the set screws and pinning, never hurts to have two secure measures.

  8. #18
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    Anyone use the GG&G front flip up/gas block? It is pinned on:



    I had my heart set on the KAC....but it is too expensive.
    "The secret to happiness is freedom, and the secret to freedom is courage." - Thucydides, c. 410 BC

  9. #19
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    I have always thought that anything that even poses a remote risk to continued operation of your firearm is a no go.

    If it's a weapon that you will stake your life on then pinned is the only way to fly, if it's a plinker or range toy then do what ever you want so it looks tacti-cool.

  10. #20
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    I had a PRI clamp-on FSB rotate a few degrees when a box was dropped on it. It was enough to misalign it with the gas port, and take the gun out of service. The PRI was properly installed, loctite on evenly torqued bolts, but it wasn't enough. I am sure the VLTOR torque test proves their sight can take the abuse, but I'm pretty sure a lot of other brands of clamp-on FSB would fail that test in a heartbeat.

    If I install another barrel mounted flip-up FSB like the PRi or ARMS 41B, I'm just going to have my gunsmith install a high crosspin, as shown in wild_wes' post. It's not practical to try to redo a pinned FSB that's already been installed, with a replacement, they're drill once, pin once. That's why clamp-on FSBs exist, but I would pin any one I installed - if it's worth taking off the gun, it's worth getting out the pin punch.

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