Adjustable gas block issue

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  • inkd

    Ultimate Member
    Aug 4, 2009
    7,512
    Ridge
    Yeah I'm going to look in to ordering one of those right now...no reason to not have one.

    EDIT: Looks like they are pretty pricey!

    When I get home and on a computer, I'll put up a link of the one I got. It wasn't bad. I got it on Amazon. Teslong rigid borescope. I got the one that you can use your phone as the viewing screen.
     

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,815
    Yeah I'm going to look in to ordering one of those right now...no reason to not have one.

    EDIT: Looks like they are pretty pricey!

    There's a very affordable one on Amazon. I have the info somewhere at home I think.

    One last thought before going through all the trouble of pulling the brake and block, you have run a string trimmer line through the gas key on the bcg all the way into bolt carrier right? Sometimes you can get a blockage in there.
     

    alucard0822

    For great Justice
    Oct 29, 2007
    17,643
    PA
    Have to make sure gas is making it where it needs to go, have seem boneheaded stuff like upside down gas tubes, or out of spec stuff that choked off gas. there are also a2 different "rifle" length gas tubes on AR308/AR10 barrels. Being the extension is longer than an AR15, a DPMS aka "AR308" barrel usually has the gas port a little further back so it can use the shorter AR15 rifle gas tube. The Armalite AR10 rifle gas system uses a gas tube about 1/4" longer to make up the difference. most of the time there is enough room in the gas key, and it seals well enough that either tube in either barrel will work. Occasionally you might get an AR10 tube long enough to bottom out in the key, peen the end over a little and cut off gas, or a shorter AR15 rifle tube in an AR10 spec barrel that leaves all of 1/4" engaged in the gas key, and can leak enough gas to affect function. Just something to check. Measure the end of the receiver extension to the gas block shoulder on the barrel. 13.25"=AR15/AR308(DPMS) length tube, 13.5"= AR10 armalite tube. Other than that, you can use a peice of thin spaghetti to verify alignment, slip the ags block forward, put the dry noodle in the hole far as it goes, break it off, slide the gas block back over and line it up. If it's right should see the noodle fall into the gas port in the block looking through the barrel when turned upside down. Turn it right side up and use a cleaning rod to snap off the noodle so it falls out. Other than that, probably going to have to take stuff apart to verify port size and make sure you don't have a defective part or gas leak somewhere else..
     

    Magnumite

    Ultimate Member
    Dec 17, 2007
    6,561
    Harford County, Maryland
    Have to make sure gas is making it where it needs to go, have seem boneheaded stuff like upside down gas tubes, or out of spec stuff that choked off gas. there are also a2 different "rifle" length gas tubes on AR308/AR10 barrels. Being the extension is longer than an AR15, a DPMS aka "AR308" barrel usually has the gas port a little further back so it can use the shorter AR15 rifle gas tube. The Armalite AR10 rifle gas system uses a gas tube about 1/4" longer to make up the difference. most of the time there is enough room in the gas key, and it seals well enough that either tube in either barrel will work. Occasionally you might get an AR10 tube long enough to bottom out in the key, peen the end over a little and cut off gas, or a shorter AR15 rifle tube in an AR10 spec barrel that leaves all of 1/4" engaged in the gas key, and can leak enough gas to affect function. Just something to check. Measure the end of the receiver extension to the gas block shoulder on the barrel. 13.25"=AR15/AR308(DPMS) length tube, 13.5"= AR10 armalite tube. Other than that, you can use a peice of thin spaghetti to verify alignment, slip the ags block forward, put the dry noodle in the hole far as it goes, break it off, slide the gas block back over and line it up. If it's right should see the noodle fall into the gas port in the block looking through the barrel when turned upside down. Turn it right side up and use a cleaning rod to snap off the noodle so it falls out. Other than that, probably going to have to take stuff apart to verify port size and make sure you don't have a defective part or gas leak somewhere else..

    Good information. Thanks.
     

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,815
    It was well worth the money. I was shocked at how good the images are.

    If I did it again I would probably go with a dedicated device to view with, instead of using my phone

    Remember, Chad used an old iphone for his fancy-schmancy bore cam.
     

    gtodave

    Member
    MDS Supporter
    Aug 14, 2007
    14,159
    Mt Airy
    There's a very affordable one on Amazon. I have the info somewhere at home I think.

    One last thought before going through all the trouble of pulling the brake and block, you have run a string trimmer line through the gas key on the bcg all the way into bolt carrier right? Sometimes you can get a blockage in there.

    Yes, I ran a pipe cleaner all the way through the gas tube to the bcg.

    Have to make sure gas is making it where it needs to go, have seem boneheaded stuff like upside down gas tubes, or out of spec stuff that choked off gas. there are also a2 different "rifle" length gas tubes on AR308/AR10 barrels. Being the extension is longer than an AR15, a DPMS aka "AR308" barrel usually has the gas port a little further back so it can use the shorter AR15 rifle gas tube. The Armalite AR10 rifle gas system uses a gas tube about 1/4" longer to make up the difference. most of the time there is enough room in the gas key, and it seals well enough that either tube in either barrel will work. Occasionally you might get an AR10 tube long enough to bottom out in the key, peen the end over a little and cut off gas, or a shorter AR15 rifle tube in an AR10 spec barrel that leaves all of 1/4" engaged in the gas key, and can leak enough gas to affect function. Just something to check. Measure the end of the receiver extension to the gas block shoulder on the barrel. 13.25"=AR15/AR308(DPMS) length tube, 13.5"= AR10 armalite tube. Other than that, you can use a peice of thin spaghetti to verify alignment, slip the ags block forward, put the dry noodle in the hole far as it goes, break it off, slide the gas block back over and line it up. If it's right should see the noodle fall into the gas port in the block looking through the barrel when turned upside down. Turn it right side up and use a cleaning rod to snap off the noodle so it falls out. Other than that, probably going to have to take stuff apart to verify port size and make sure you don't have a defective part or gas leak somewhere else..
    I bent the end of a small piece of wire to "measure" the distance to the port on the gas block...they appear to be the same distance, but without a bore scope to verify, I can't be certain they align perfectly.

    One thought I had was: Is there a difference between AR15 and AR10 gas blocks? I saw nothing differentiating in any of the blocks I looked at, which made me think they were interchangeable. If they aren't, that could be my problem.
    Thanks!



    I reached out to the manufacturer to ask for help, but I haven't heard back yet. Hopefully they offer something useful. I think I'll get that borescope and confirm alignment in the meantime...can't hurt.
     

    Bountied

    Ultimate Member
    Apr 6, 2012
    6,888
    Pasadena
    Yes, I ran a pipe cleaner all the way through the gas tube to the bcg.


    I bent the end of a small piece of wire to "measure" the distance to the port on the gas block...they appear to be the same distance, but without a bore scope to verify, I can't be certain they align perfectly.

    One thought I had was: Is there a difference between AR15 and AR10 gas blocks? I saw nothing differentiating in any of the blocks I looked at, which made me think they were interchangeable. If they aren't, that could be my problem.

    Thanks!



    I reached out to the manufacturer to ask for help, but I haven't heard back yet. Hopefully they offer something useful. I think I'll get that borescope and confirm alignment in the meantime...can't hurt.

    Remember you need at least a 1.5mm gap from the shoulder of the barrel, use a credit card to gauge it. Most barrels are set up for a delta ring which accounts for that gap.
     

    gtodave

    Member
    MDS Supporter
    Aug 14, 2007
    14,159
    Mt Airy
    Remember you need at least a 1.5mm gap from the shoulder of the barrel, use a credit card to gauge it. Most barrels are set up for a delta ring which accounts for that gap.

    The block was hard up against the shoulder from the 'smith, and I put it back that way. It will be interesting to see where that lines up when my scope arrives.
     

    alucard0822

    For great Justice
    Oct 29, 2007
    17,643
    PA
    Yes, I ran a pipe cleaner all the way through the gas tube to the bcg.


    I bent the end of a small piece of wire to "measure" the distance to the port on the gas block...they appear to be the same distance, but without a bore scope to verify, I can't be certain they align perfectly.

    One thought I had was: Is there a difference between AR15 and AR10 gas blocks? I saw nothing differentiating in any of the blocks I looked at, which made me think they were interchangeable. If they aren't, that could be my problem.

    Thanks!



    I reached out to the manufacturer to ask for help, but I haven't heard back yet. Hopefully they offer something useful. I think I'll get that borescope and confirm alignment in the meantime...can't hurt.


    Pics and specs. You basically have 5 gas lengths on AR10/AR308s, and some mix and match them, Have a Faxon build, mid-length in the description, noticed less than 1/4" of gas tube was engaging the key, measured it and turned out to be an AR10 carbine spec, got the proper tube and all set.
    https://truenortharms.com/ar15_default_store_view/gas-tubes-for-ar-10-dpms-308.html

    no real difference in blocks other than some get clogged or burnt due to the massive increase in gas volume, but SA makes a solid block, and works fine in either.

    The block was hard up against the shoulder from the 'smith, and I put it back that way. It will be interesting to see where that lines up when my scope arrives.

    I dimple EVERY barrel, at least 1 directly opposite from the gas port as that is where the front set screw will seat, and it helps line it up. Some barrels sit tighter with some gas blocks, some have a bit more of a gap, but it's usually around .050". SA gas blocks have a relatively large port, so it's not all that picky with alignment, but you also want to make sure it's not binding on the gas tube, if it's off a little the tube will rub the side of the key, wear and cause leakage. This gas block was lined up by measurements/dimple, then verified dead center with a borescope. Just about all of mine fit the same way as this one pictured. Also pictured is about how much gas tube should be inside the carrier WITH THE CHARGING HANDLE IN PLACE, usually about centered in the cam cutout. SA gas block and AR308/rifle length gas on an Aero M5/BA fluted match barrel.

    20210528_133343.jpg

    20210528_133459.jpg
     

    SkiPatrolDude

    Ultimate Member
    MDS Supporter
    Oct 24, 2017
    3,331
    Timonium-Lutherville
    Remember you need at least a 1.5mm gap from the shoulder of the barrel, use a credit card to gauge it. Most barrels are set up for a delta ring which accounts for that gap.

    While this is somewhat true, you still shouldn't see major issues if the gas block is snugged right up against the shoulder.

    The hole in the gas block is massive compared to barrel port, so you'd have to be pretty far off of center to have major issues.

    It's not uncommon to see lower end AR manufacturers turning our rifles with the block right against the shoulder and most of them still run OK.

    Not optimal, but not something that immediately warrants a full tear down.

    Just my 0.02.
     

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,815
    Pics and specs. You basically have 5 gas lengths on AR10/AR308s, and some mix and match them, Have a Faxon build, mid-length in the description, noticed less than 1/4" of gas tube was engaging the key, measured it and turned out to be an AR10 carbine spec, got the proper tube and all set.
    https://truenortharms.com/ar15_default_store_view/gas-tubes-for-ar-10-dpms-308.html

    no real difference in blocks other than some get clogged or burnt due to the massive increase in gas volume, but SA makes a solid block, and works fine in either.



    I dimple EVERY barrel, at least 1 directly opposite from the gas port as that is where the front set screw will seat, and it helps line it up. Some barrels sit tighter with some gas blocks, some have a bit more of a gap, but it's usually around .050". SA gas blocks have a relatively large port, so it's not all that picky with alignment, but you also want to make sure it's not binding on the gas tube, if it's off a little the tube will rub the side of the key, wear and cause leakage. This gas block was lined up by measurements/dimple, then verified dead center with a borescope. Just about all of mine fit the same way as this one pictured. Also pictured is about how much gas tube should be inside the carrier WITH THE CHARGING HANDLE IN PLACE, usually about centered in the cam cutout. SA gas block and AR308/rifle length gas on an Aero M5/BA

    This. Most GBs have a port wide enough to overcome that gap discrepancy. Front to back alignment is not as critical as rotational alignment.
     

    gtodave

    Member
    MDS Supporter
    Aug 14, 2007
    14,159
    Mt Airy
    Pics and specs. You basically have 5 gas lengths on AR10/AR308s, and some mix and match them, Have a Faxon build, mid-length in the description, noticed less than 1/4" of gas tube was engaging the key, measured it and turned out to be an AR10 carbine spec, got the proper tube and all set.
    https://truenortharms.com/ar15_default_store_view/gas-tubes-for-ar-10-dpms-308.html

    no real difference in blocks other than some get clogged or burnt due to the massive increase in gas volume, but SA makes a solid block, and works fine in either.

    I dimple EVERY barrel, at least 1 directly opposite from the gas port as that is where the front set screw will seat, and it helps line it up. Some barrels sit tighter with some gas blocks, some have a bit more of a gap, but it's usually around .050". SA gas blocks have a relatively large port, so it's not all that picky with alignment, but you also want to make sure it's not binding on the gas tube, if it's off a little the tube will rub the side of the key, wear and cause leakage. This gas block was lined up by measurements/dimple, then verified dead center with a borescope. Just about all of mine fit the same way as this one pictured. Also pictured is about how much gas tube should be inside the carrier WITH THE CHARGING HANDLE IN PLACE, usually about centered in the cam cutout. SA gas block and AR308/rifle length gas on an Aero M5/BA fluted match barrel.
    Thanks for the info. Since it was working perfect before the gas block (and it took two trips to Armalite to get it that way), I'm going to assume that the gas tube is correct. I'll try to snap some pictures soon to share though.

    SA hasn't gotten back to me yet, which is disappointing. My borescope is supposed to arrive this week, so I will be able to verify more when that arrives. Really don't want to take it back to the 'smith since it's an hour each way, and they are really backed up right now.
     

    gtodave

    Member
    MDS Supporter
    Aug 14, 2007
    14,159
    Mt Airy
    Well, I don't know what TF to do next. Alignment is perfect. I have air moving through the buffer tube. I can see the SA block adjusting when I turn it while looking through the scope. Everything seems to be as it should. Maybe the block is bad...but I don't know how to test for that (other than it not working).

    Here's a pic of the adjustment all the way closed.
     

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    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,815
    I'd love to see a pic of the block(sans rail) and the portion of the barrel forward of the GB
     

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,815
    So, if you turn the GB all the way in(clockwise right hand turns?), then turn it out 4-4.5 turns(left hand turns?), it should be wide open just like a standard GB. It should be unrestricted. Turning it clockwise from there will result in restricting the gas flow, pushing any excess gas out the muzzle. The gun should function as it did before the the change to the new GB in the unrestricted mode.

    No need discussing the bleed-off function at this point because I don't think that is causing the problem. Yet.
     

    gtodave

    Member
    MDS Supporter
    Aug 14, 2007
    14,159
    Mt Airy
    So, if you turn the GB all the way in(clockwise right hand turns?), then turn it out 4-4.5 turns(left hand turns?), it should be wide open just like a standard GB. It should be unrestricted. Turning it clockwise from there will result in restricting the gas flow, pushing any excess gas out the muzzle. The gun should function as it did before the the change to the new GB in the unrestricted mode.

    No need discussing the bleed-off function at this point because I don't think that is causing the problem. Yet.
    Yeah 4 turns completely opened up the port. Interesting that you say more would restrict it more. I might try to run it like this and see what happens. Can't get to the range any time soon though
     

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