AR10 Build Cycle Issues

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  • MChenko

    Member
    Mar 1, 2019
    4
    Hello,

    This is my first post, so thank you to all who take the time to read it and reply. I appreciate your insights.

    I finished my first AR10 build a few months back but had trouble with the bolt not cycling fully. It is an Aero build with a 20inch barrel and rifle length gas system. The bolt cycles enough to eject the spent case but not enough to pick up the next round. I dropped it off to a local gun shop in December for them to work on it while I was away at work for a few months. Unfortunately, they didn’t get around to it so I picked it up to work on it myself. I took my muzzle brake and hand guard off and checked the gas block was aligned properly. I will be taking it to try it out again tomorrow morning.

    If that does not work I think my next step will be to start changing buffers and springs. Currently I am using a DPMS rifle length buffer and spring.

    Does anyone have any suggestions for trouble shooting the issue or recomendations for a shop I can take it to in order to have it looked at if I cannot solve the problem myself ?

    Again,

    I appreciate all the help.
     

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    LGood48

    Ultimate Member
    Feb 3, 2011
    5,959
    Cecil County
    No help with your issues, but welcome to the forum. I suggest you stop by the INTRODUCTIONS thread and do a proper intro and tell us a bit about yourself. :)
     

    danb

    dont be a dumbass
    Feb 24, 2013
    22,704
    google is your friend, I am not.
    First thing I would check is that the gas port is correctly aligned with the gas block, free of debris, and that the tube is free of blockages. What barrel and gas block are you using? Did you put the tube in the gas block or did it come installed? The gas tube might not be aligned in the gas block

    You wont really know until you shoot it whether that fixed it. I doubt its the buffer and spring. If anything, AR10s are over gassed. You ought to be able to throw a heavy buffer and spring in there and it still cycles.

    The second thing is I would look at is the BCG to make sure the gas key looks ok and is firmly staked.

    Its also possible that you got a bad batch of ammo. rare but it does happen. Try different ammo, see how it cycles.
     

    Neutron

    Ultimate Member
    MDS Supporter
    Nov 20, 2014
    1,532
    severna park
    I had the same issue with one. The problem was not enough lube. They like to run very wet. Try it and see if that doesn't fix your problem.
     

    smdub

    Ultimate Member
    MDS Supporter
    Nov 14, 2012
    4,644
    MoCo
    Welcome.
    It would help if you put your general location in your profile so we could suggest what places are close by to you for help.
     

    MChenko

    Member
    Mar 1, 2019
    4
    Hello,

    Sorry it has been a few days since my original post. Unfortunately due to the weather I was unable to shoot it before leaving for a two week trip for work. Until I get back home I won’t know if the problem is remedied or not. To answer your question I installed the gas tube in the gas block myself. The barrel is a barrel from Aero.

    What did you mean when you asked is the tube aligned in the gas block? It is a low profile gas block but I am unsure of the manufacturer. It when I installed it I just tapped the pin into place and made sure the hole in the tube was faxing the right way.

    I am from Frederick area but travel a lot through Western Maryland as well.

    Thank you all for the advice. Sorry I couldn’t give an update on the progress before I left but I will be sure to update the thread when I get home and shoot it.
     

    KIBarrister

    Opinionated Libertarian
    MDS Supporter
    Apr 10, 2013
    3,923
    Kent Island/Centreville
    1. cut to the chase, get an adjustable gas block. They ought be mandatory on -10's

    2. buffer spring and weight may or may not be part of your problem. I had issues with a 6.5 that an adjustable gas block helped but not fully, buffer and spring (flat wire) sorted it the rest of the way out.

    3. Mags? If you only have one brand, buy another and see if that helps.

    4. Any pressure signs on the spent casings? You didn't say, but I'm assuming 7.62, so there shouldn't be... OTOH, you said build, so not a bad idea to keep an eye on your brass.

    5. Is the rifle broken in? If its brand new, lube it and shoot it. My first -10 shot like sh!t the first 50 rounds despite standard clean and lube; ran it wet for the next 50 and GTG ever since.

    I would say #1 is mandatory irrespective. I would try #5 first, then #3, keep an eye on #4, and #2 is cheap enough just do it. (I probably could have numbered those better).
     

    SWO Daddy

    Ultimate Member
    Jun 18, 2011
    2,468
    High probability of a misaligned gas block / tube. You should put an adjustable gas block in if you haven't already.
     

    danb

    dont be a dumbass
    Feb 24, 2013
    22,704
    google is your friend, I am not.
    What did you mean when you asked is the tube aligned in the gas block? It is a low profile gas block but I am unsure of the manufacturer. It when I installed it I just tapped the pin into place and made sure the hole in the tube was faxing the right way.

    I think you are asking me, so I will answer. If it were me I would remove the gas block and check that the hole on the tube lines up correctly with the hole in the gas port on the block (you can probably do this visually). Check for carbon or debris. If you put rocksett or loctite on the gas block screws, it might have run and clogged the gas port, then turned to carbon. As others have noted, I would put an adjustable gas block on the barrel (SLR makes a nice one, but there are others), because its an AR10. Short of that, inspect the whole gas system end to end. I would also inspect your BCG and make sure your gas key is tight. I doubt its the buffer and spring, but you might double check the detent pin that holds your buffer in the tube - plausible that its not right and the bcg is riding on that.

    But as others have noted, might try simply lubing it up first. A good lube job on an AR10 goes a long way, many like to run sloppy wet. Especially if you were running it on a cold day where some lube tends to gum up and cold metal shrinks.
     

    Oceancity311

    Member
    Feb 25, 2019
    14
    Had same issue with mine I did everything suggested thus far and it didn't help I ended up drilling out the gas port in the barrel to 1/8 of an inch also make sure you have the proper gas tube there is dpms and there is an armalite gas tube the armlight gas tube is 1/4 of an inch longer. Your gas tube should come out half way into the cam pin cut out in your upper. If it doesn't get an armalite gas tube it will fully seat into the gas key on your bolt carrier group.
     

    MChenko

    Member
    Mar 1, 2019
    4
    Hello all thanks for all the questions. I was shooting federal match ammo. I have not yet switched to an adjustable gas block because I am out of town until next Sunday so I have not been able to work on it. I do not know anyone in the area with a 308 upper I could test out when I get home. I do not have a flat wire spring so I may look into that at first.

    Drilling the barrel would be my last resort and I would take it to a gunsmith to troubleshoot before I did that too.

    Thank you again for all the suggestions.
     

    Boats

    Beer, Bikes n Boomsticks
    Mar 13, 2012
    4,073
    Howeird County
    Is that a carbine or rifle length gas system?
    What is barrel length?

    In sone cases a short ish barrel and gas system and smallish gas port can cause short stroking by not letting enough gas back down the gas tube before the bullet exits the barrel.


    I would bet that the spring weight is too heavy and/or the buffer is too heavy. Ordinarily, AR10s produce enough gas to overcome buffer parts causing short stroking, but not always.

    I would start with a Superlative Arms adjustable gas block. If you are running it wide open and it still short strokes, then look at lightening up spring and buffer.
     

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