Pennsylvania Firearm Owners Association
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  1. #1
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    Default Dimpling barrel for AR gas block

    I have a PSA FN barreled upper with keymod handguard and it has a low profile gas block with two set screws. It's never given me a problem so I'm leaning towards doing nothing. But it's my go-to rifle so I wanted to at least explore opinions to increase it's robustness.

    Should I dimple the barrel in one spot for the set screw to avoid a possibility of rotation one day? The one screw is accessible without taking off the handguard. The gas block is obviously already installed so it's positioned correctly and the screw hole would serve as the guide. I could just drill in the 1/32" or so for the dimple, then reinstall the screw with some high heat threadlocker. Probably would take 10 minutes.

    Yay or nay?

  2. #2
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    Default Re: Dimpling barrel for AR gas block

    Big chance you’ll wipe out your threads if you spot drill through the hole. You get a transfer center punch that fits the hole. You use a vice and drill press to make the dimple. If you half ass it you end up in bubba town. Drilling straight holes in round steel isn’t easy without proper tools and prep.
    The Gun is the Badge of a Free Man

  3. #3
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    Default Re: Dimpling barrel for AR gas block

    Quote Originally Posted by Gunsnwater View Post
    Big chance you’ll wipe out your threads if you spot drill through the hole. You get a transfer center punch that fits the hole. You use a vice and drill press to make the dimple. If you half ass it you end up in bubba town. Drilling straight holes in round steel isn’t easy without proper tools and prep.

    What he said.

    Do it right the 1st time and in order to do that you need to remove the handguard, and gas block dimple the barrel, torque everything down correctly and reinstall with new thread locker.

  4. #4
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    Default Re: Dimpling barrel for AR gas block

    Quote Originally Posted by Gunsnwater View Post
    Big chance you’ll wipe out your threads if you spot drill through the hole. You get a transfer center punch that fits the hole. You use a vice and drill press to make the dimple. If you half ass it you end up in bubba town. Drilling straight holes in round steel isn’t easy without proper tools and prep.
    Thank you. Makes total sense. So the handguard and gas block would need to be removed. I did see a jig that makes lining up the holes foolproof so I could get that.

    What's the consensus on actually needing to dimple?

  5. #5
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    Default Re: Dimpling barrel for AR gas block

    Quote Originally Posted by jthrelf View Post
    Thank you. Makes total sense. So the handguard and gas block would need to be removed. I did see a jig that makes lining up the holes foolproof so I could get that.

    What's the consensus on actually needing to dimple?
    PSA uses high temp thread locker which should be enough. Unless you plan on running mag dump after mag dump and really hearing that barrel and gas block up you most likely will never have an issue. Itís just one of those feel good inside things in my opinion. My main two rifles are pinned the rest are just high them thread locked.

  6. #6
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    Default Re: Dimpling barrel for AR gas block

    Do manufacturers dimple? If so, then it might be a good idea, but bear in mind if manufacturers are doing it, they are doing it as a cost-effective reduction in send-backs and bad press. In other words, it might be over-kill for you, worthwhile insurance for them

    On the other hand, if they aren't, that seems a very good indicator that it isn't needed. Two set screws of proper design and material are going to make impression cuts in the barrel. If the block ever did come loose, the set screws could be relocated to their "nests".

    If you have the material to work with, you could drill and tap for set screws to secure the set screws. I'd be hesitant to use high-heat LocTite. It could prevent a future repair or maintenance or create need to spoil the area.
    Legislating to prevent people's acts is fantasy

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    Default Re: Dimpling barrel for AR gas block

    A lot of manufacturers use pointed tip set screws that basically make their own dimples. Remove the set screw you can get to and see if you can see if the screw made a "dimple" or other indentation. If it did, put a drop of red LocTite on the screw and reinsert and torque. The red makes the screw tougher to remove but the high temp stuff will make it darn near impossible.
    Ron USAF Ret E-8 FFL01/SOT3 NRA Benefactor Member

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    Default Re: Dimpling barrel for AR gas block

    Quote Originally Posted by Xringshooter View Post
    A lot of manufacturers use pointed tip set screws that basically make their own dimples. Remove the set screw you can get to and see if you can see if the screw made a "dimple" or other indentation. If it did, put a drop of red LocTite on the screw and reinsert and torque. The red makes the screw tougher to remove but the high temp stuff will make it darn near impossible.
    Red will degrade once that barrel heats up. If this is going to be a rifle thatís going to see use and your looking to avoid issues then use high temp unless you have a pinned gas block.

  9. #9
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    Default Re: Dimpling barrel for AR gas block

    I never had a gas block loosen and I don't dimple or lock tight, I just lock them down tight. Shot thousands of rounds through more then one build. If you torque the screws down tight, the screws will dig in enough that you will see marks in the barrel if you want to drill it just take it off and you will see where the marks are.
    Last edited by :-); June 29th, 2019 at 11:36 PM.

  10. #10
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    Default Re: Dimpling barrel for AR gas block

    Quote Originally Posted by jthrelf View Post
    Thank you. Makes total sense. So the handguard and gas block would need to be removed. I did see a jig that makes lining up the holes foolproof so I could get that.

    What's the consensus on actually needing to dimple?
    First time the block gets a lateral hit you'll be glad you dimpled it. Get the hardened steel jig. 6months after buying a tool and for the rest of your life, you won't remember what you paid for it, but you'll still have it.

    Building right is a pride in workmanship you can feel even on the economy builds. The practice in methods and procedures will be their for that special build you'll inevitably find yourself in the middle of.
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