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Thread: Aftermarket Gas Block on LE6920

  1. #1
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    Aftermarket Gas Block on LE6920

    I have a 16” LE6920 & wanted to swap A2 sight/gas block for a BCM. The BCM I believe uses set screws to secure it to the barrel. My question is, are the cutouts on the barrel for the taper pins going to be an issue with using a set screw attachment option like the one found on the BCM gas block. I’m already aware that I could just chop the sight down but would prefer to not take a cutoff wheel & grinder to my gun. I have researched as much as I can & cannot find any info on this particular issue. I’m hoping someone here may already have some experience with this topic. Thanks!


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  2. #2
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    Why do you want switch to a LP GB? To run a longer rail?

    If so a better solution might be to shave down the FSP....which is what I’m doing right now to a 6920 barrel. I was about to do it myself but ADCO only charges $30 and would probably do a prettier job...so I sent it to them.

    I’d much prefer a pinned shaved down FSP than a new BCM set screw GB. More secure plus you won’t have two empty pin channels on the barrel to get rusty. Mind you this is what you get when you buy a Colt OEM 2
    "A flute without holes, is not a flute. A donut without a hole, is a Danish." - Ty Webb

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    Quote Originally Posted by OldState View Post
    Why do you want switch to a LP GB? To run a longer rail?

    If so a better solution might be to shave down the FSP....which is what I’m doing right now to a 6920 barrel. I was about to do it myself but ADCO only charges $30 and would probably do a prettier job...so I sent it to them.

    I’d much prefer a pinned shaved down FSP than a new BCM set screw GB. More secure plus you won’t have two empty pin channels on the barrel to get rusty. Mind you this is what you get when you buy a Colt OEM 2


    Yes. Longer rail.



    - FISH5742

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    Quote Originally Posted by FISH5742 View Post
    Yes. Longer rail. - FISH5742
    I don't mean to offend, but I see you are a new member.

    If you are using the cut down FSB and wanting a longer rail you will need to make sure you get one that is compatible with the Colt/GI barrel nut.

    Or, you could remove the FSP and reuse the taper pins if they were not damaged during removal. For peace of mind you might want to use Loctite 640 sleeve retainer on the assembly: https://www.amazon.com/Loctite-37424.../dp/B0002KKTIG

    Most guys think this guy is legit, so here;s a video on shaving down the FSB, you can do it! https://www.youtube.com/watch?v=5sBqDpi-Cb4

    Some folks will advise against reusing the taper pins, but there are more technical applications than the M4 FSB that reuse undamaged taper pins.
    Last edited by 26 Inf; 01-20-20 at 17:19.
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    Quote Originally Posted by 26 Inf View Post
    I don't mean to offend, but I see you are a new member.

    If you are using the cut down FSB and wanting a longer rail you will need to make sure you get one that is compatible with the Colt/GI barrel nut.

    Or, you could remove the FSP and reuse the taper pins if they were not damaged during removal. For peace of mind you might want to use Loctite 640 sleeve retainer on the assembly: https://www.amazon.com/Loctite-37424.../dp/B0002KKTIG

    Most guys think this guy is legit, so here;s a video on shaving down the FSB, you can do it! https://www.youtube.com/watch?v=5sBqDpi-Cb4

    Some folks will advise against reusing the taper pins, but there are more technical applications than the M4 FSB that reuse undamaged taper pins.
    No offense taken. I am new to the forum but not to the AR 15/M16/M4 series rifle. I am aware that the barrel nut will need to be replaced but thanks for looking out. The BCM MCMR handguard comes with a barrel nut as well as a wrench & a few other pieces of hardware to attach the rail to the nut. This will make the 3rd handguard I’ve had on this rifle among others that I have swapped out in the past for friends. I finally decided to extend the rail out to 15”. Thanks for the info about having the A2 shaved down. I was unaware that you could get it done professionally. I was under the impression that it was typically a DIY, shade tree gunsmithing hack job. I think that may be a better choice rather than putting on an aftermarket item & would maintain original Colt equipment a little better.


    - FISH5742

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    I would shave the stock one down.
    Last edited by the AR-15 Junkie; 01-22-20 at 07:07.

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    Thanks for all the info! I think I’m gonna go with the DIY shave job. Ordered some perma blue from Brownells & we will see how it goes.


    - FISH5742

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    I've been using a BCM lo-pro gas block on my 6920 for about 10 years (originally with a DD quad rail, now with an M-Lok rail)...zero issues. I didn't dimple my barrel, and I've never had the block or set screws loosen over the course of @ 5k rounds.


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    Quote Originally Posted by kwb377 View Post
    I've been using a BCM lo-pro gas block on my 6920 for about 10 years (originally with a DD quad rail, now with an M-Lok rail)...zero issues. I didn't dimple my barrel, and I've never had the block or set screws loosen over the course of @ 5k rounds.

    Did the set screw drop into the taper pin groove? & is the other taper pin groove still exposed?


    - FISH5742

  10. #10
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    No issue with the set screw and pin groove interfacing.

    The front pin groove is visible, but not noticeable...

    Last edited by kwb377; 01-21-20 at 19:59.

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