Gas problems?

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  • Mgderf

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    O.K. I'm a bit confused.
    A friend brought me a new AR15 build he just finished to trouble-shoot. It's a 16" .223 Wylde build.
    It will fire the first round, and chamber the second, but the trigger will not reset.

    The trigger DOES reset if you pull the hammer back by hand, or if you pull the charging handle back and release, but not after a shot.
    This same guy had me look at another AR he recently built that had the same issue. On that one the gas block was askew just enough to under-gas the system.

    I've torn the new(er) one down twice now, and I'd swear I have the gas block lined up.
    Is it possible to send the bolt back far enough to pick up the next round, without moving rearward far enough to reset the trigger?

    If this is not the problem, I was thinking too heavy a buffer/spring set-up?

    Any ideas?
     

    Cameramonkey

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    Check the lower. I just tried to get mine to eject without resetting and could not. In fact I could hear mine cock when the brass was about halfway out.

    Sounds like the hammer could be riding the bolt down.
     

    churchmouse

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    If it is chambering the next round then the cycle length is fine. You have enough gas.
    Are you pulling the rear pin to manually cock the hammer when this occurs or just cycling the BCG...???
    Issue is in the hammer/ignition controls.
     

    55fairlane

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    sounds to me like the holes for the pins are out of spec, or the FCG is faulty,

    try swapping parts from the other AR that runs fine, see if the problems follow to the other gun
     

    Mgderf

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    If it is chambering the next round then the cycle length is fine. You have enough gas.
    Are you pulling the rear pin to manually cock the hammer when this occurs or just cycling the BCG...???
    Issue is in the hammer/ignition controls.

    I've come to the same conclusion, but still can't see the problem.
    Have to fiddle with it more tonight.

    Got things to see and people to do right now...
     

    6mm Shoot

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    The problem is in the fire control system. Check to see if one of the springs are in wrong.
     

    Mgderf

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    The problem is in the fire control system. Check to see if one of the springs are in wrong.

    Nope. Not it.
    I completely disassembled the FCG, inspected, cleaned, lubed and re-installed.
    Same scenario.
    It will reset the trigger when I pull the charging handle back, or manually.

    It must be in the interface between the sear/disconnect and hammer.
    If I pull the charging handle and cock the hammer, then pull and release the trigger, all is normal.

    If I hold the trigger back and try to reset the trigger, the disconnect grabs the hammer, but will not release it to the sear when the trigger is released.

    Brand new Anderson lower and LPK.
    I'm guessing a bad parts kits, though I can't see the issue.
     

    sig1473

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    Brand new Anderson lower and LPK.
    I'm guessing a bad parts kits, though I can't see the issue.

    That's your problem right there. I don't know why people skimp on AR parts. I just got done tearing down a lower and replaced all the parts that were CMMG. The parts were/are complete junk. Invest in some quality parts i.e. Colt, DD, Sionics, SOLGW, LMT
     

    NyleRN

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    It's sounds like a disco problem. It's a SLIGHT chance the gun is so overgassed that the bcg is out running the hammer/disco engagement.

    ETA: Have you by chance tried a heavier buffer? Are you getting gas to the face when shooting it?
     

    smooth308

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    A friend of mine had the same issue with one of his builds turned out that he put the diconneter spring in upside down the little spring inside the trigger the wider end of the spring goes to the bottom check it to make sure its in properly.
     

    Mgderf

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    Fixed it!


    Well, that was interesting.
    Turns out it was the fire control group.
    Not sure if it was the disconnect or the hammer, but one of them must have had a burr, or a sharp edge.

    I noticed that when you pulled and held the hammer back before letting the hammer up, the disconnect would catch the hammer, as it should.
    The problem was, when you released the trigger, the disconnect would not release the hammer to the sear.
    You had to push the trigger forward manually to reset it.

    I removed the upper and sat down with the lower in my lap.
    I put a dab of Lubriplate engine assembly lube on the disconnect, and started playing with it.

    I pulled the trigger back and held it, then pulled the hammer down until the disconnect grabbed hold.
    I let loose of the hammer and pushed the trigger forward until the disconnect released the hammer.
    Rinse and repeat for about an hour.

    After 10 minutes I could feel a change in the disconnect.
    It was exponentially easier to reset the trigger with each cycle I performed manually.
    Soon the disconnect would release when the trigger was released.

    This was a new problem for me, and it took a while for me to diagnose, but relatively easy to fix, once the issue was identified.

    Gave myself a good pat on the back.
    I'm getting to know my way around the AR platform MUCH better than I ever did in the service.
     

    Reverend Dreed

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    Jan 24, 2016
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    when I read gas problem my first thought was to recommend gas x . Glad you found the problem, and that I kept my smart a** comments out of the thread until the problem was resolved.
     
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