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  1. #1
    Paper Hunter Little Dutch's Avatar
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    Default Adjustable Gas Block advice - AR-10

    My AR-10 cycles 100% of the time without a suppressor, but has some failure to eject issues with a suppressor. This leads me to think I'll be putting on an adjustable gas block in the near future. I have never purchased one, and would like to get your opinions.

    The current handguard covers the gas block by a few inches. If possible, I would like to keep that handguard and get a gas block that I can adjust with a long hex wrench, or something similar. Any recommendations?

    It's a Gen 2 Palmetto upper if it makes a difference.
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  2. #2
    Grand Master Know It All
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    First I'd suggest you take a close look at what's going on during the failures. Supressors tend to over gas actions when installed on normally functioning rifles. Failure to eject, in my experience, is from under-gassing or other issues. I'm not saying it's impossible that over gassing is causing failure to eject, it just tends to be lower on the list.

    How many rounds thru it supressed and un supressed? Any changes? New ammo? What ammo? What is the ejection pattern change when you add the can?

  3. #3
    Paper Hunter NukeRJ's Avatar
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    There are multiple types of FTE. So let's start with exactly what happens to the spent brass when it fails to eject.

    Stovepipe- most likely overgassed as the brass did not have time to be flung out by the ejector while traveling rearward. It then hit the rear of the ejection port and was caught by the bolt on the way back onto battery.

    Bolt override - worn or weak extractor or bad magazine pushing rounds off the bolt face before ejection.

    Double feed with spent cartridge - bad ejector or a bad mag again or combo.

    Spent cartridge rechambered - classic FTE short stroke from undergassing.

    There are several more FTE failures. But most likely with a supressor, It's overgassed and has increased bolt speed rearward which can do all sorts of funny stuff, including stovepipe and doubles with spent casing in my limited experience.

    I like superlative and seekins gas blocks. I've run JP, seekins, superlative and custom made for reference.
    Last edited by NukeRJ; 03-07-2019 at 17:32.

  4. #4
    Gong Shooter
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    I went with the SLR adjustable on one of my 308 ARs. It's adjustable from the front via a long hex wrench.

  5. #5
    Paper Hunter Little Dutch's Avatar
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    Quote Originally Posted by Wulf202 View Post
    First I'd suggest you take a close look at what's going on during the failures. Supressors tend to over gas actions when installed on normally functioning rifles. Failure to eject, in my experience, is from under-gassing or other issues. I'm not saying it's impossible that over gassing is causing failure to eject, it just tends to be lower on the list.

    How many rounds thru it supressed and un supressed? Any changes? New ammo? What ammo? What is the ejection pattern change when you add the can?
    It is fairly new still; I have less than 500 rounds through it total. However, it cycles 100% of the time with the suppressor off so it's likely the problems are caused by having the suppressor on, which points directly to being an overgassed issue.
    No changes other than adding the suppressor. I am using the same Hornady American Gunner factory ammunition. I considered checking the ejection pattern, but it's hard to do at the indoor range because the case deflects off the divider wall immediately and I didn't think it worth the effort.


    Quote Originally Posted by NukeRJ View Post
    There are multiple types of FTE. So let's start with exactly what happens to the spent brass when it fails to eject.

    Stovepipe- most likely overgassed as the brass did not have time to be flung out by the ejector while traveling rearward. It then hit the rear of the ejection port and was caught by the bolt on the way back onto battery.

    Bolt override - worn or weak extractor or bad magazine pushing rounds off the bolt face before ejection.

    Double feed with spent cartridge - bad ejector or a bad mag again or combo.

    Spent cartridge rechambered - classic FTE short stroke from undergassing.

    There are several more FTE failures. But most likely with a supressor, It's overgassed and has increased bolt speed rearward which can do all sorts of funny stuff, including stovepipe and doubles with spent casing in my limited experience.

    I like superlative and seekins gas blocks. I've run JP, seekins, superlative and custom made for reference.
    Thanks for the gas block opinions. I appreciate it. It's stovepiping the spent cartridge and jamming it up with the next round. It's extremely likely to be an overgass issue, because it cycles 100% of the time without the suppressor.

    Quote Originally Posted by The Rat View Post
    I went with the SLR adjustable on one of my 308 ARs. It's adjustable from the front via a long hex wrench.
    Excellent, thank you. A lot of them I've looked at are adjustable from the side. I spent some time examining my hand-guard last night and I'm not convinced I'll have access to a side adjustment.


    These Anderson adjustable blocks are discontinued and about half price right now. I am strongly considering taking a chance on one, because I like the price point and it's adjustable from the front.
    https://www.opticsplanet.com/anderso...ock-ltica.html
    Last edited by Little Dutch; 03-08-2019 at 09:52.
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  6. #6
    Varmiteer DireWolf's Avatar
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    Quote Originally Posted by Little Dutch View Post
    It's stovepiping the spent cartridge and jamming it up with the next round. It's extremely likely to be an overgass issue, because it cycles 100% of the time without the suppressor.
    Before replacing the gas block, I would strongly suggest trying a heavier buffer (H2/H3) and see if that resolves the issue. May still need to reduce gas volume/rate, but start with mass to slow things down a bit...

    (have dealt with this exact issue several times now...)
    Last edited by DireWolf; 03-08-2019 at 11:22.

  7. #7
    Paper Hunter Little Dutch's Avatar
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    Quote Originally Posted by DireWolf View Post
    Before replacing the gas block, I would strongly suggest trying a heavier buffer (H2/H3) and see if that resolves the issue. May still need to reduce gas volume/rate, but start with mass to slow things down a bit...

    (have dealt with this exact issue several times now...)
    Okay, thanks. I will take a look to see what's out there.
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  8. #8
    Paper Hunter Little Dutch's Avatar
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    I took the AR-10 to the range over lunch again today. It's ejecting brass at 1:00 with the suppressor on.
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  9. #9
    Industry Partner BPTactical's Avatar
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    Superlative Arms adjustable gas block.
    It is a "bleed off" type which allows excess gas to bleed off instead of dead heading.
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