AR15 cycles correctly but trigger will not cock after the first shot.

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    Mlofties

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    I recently received a home built AR15 from a friend. It worked well when I first got it. I changed the hand guards and stock and it continued to work well. But now it has developed an issue that I am unable to figure out. I need some help. Now after shooting the first round, the spent casing will be ejected and new round is loaded but will not shoot because the trigger is not cocked. I manually cycle the live round out of the chamber, load another round and it will fire that round, but then repeat the previous steps. I have put one round in the magazine, manually cycled it, fired it and the bolt locked back. I assume that means the gas block and gas pressure is OK. With the lower removed from the upper receiver I can manually lock back the trigger and it seems to function properly.

    I have an Anderson lower with a PSA MPI bolt carrier group. Not sure what the upper is - no distinguishing marks. I am shooting American Eagle 50 gr jacketed hollow points.

    Any ideas would be appreciated.

    Mike
     
    DFSgunner

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    It could be under gassed or a buffer spring issue since it will fire one round fine. I'd make sure your gas block is seated properly since you swapped hand guards
    Also check your hammer and trigger engagement surfaces, you might have sheared something. Next I would check the disconnecter and it's spring.
     
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    FrommerStop

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    There is a section here for the AR15 for such posts. I am not an expert on the AR15, but normally when a semi-auto is capable of feeding and ejecting a fired round it is the fire control group that needs to be looked at closely. I assume that ejection is normal. I would look closely at the how the hammer, disconnetor, and sear are set up and especially their springs. The hammer is ridding down it appears with the bolt carrier and not getting cocked.

     
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    TackleberryMCS

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    Mlofties said:
    I recently received a home built AR15 from a friend. It worked well when I first got it. I changed the hand guards and stock and it continued to work well. But now it has developed an issue that I am unable to figure out. I need some help. Now after shooting the first round, the spent casing will be ejected and new round is loaded but will not shoot because the trigger is not cocked. I manually cycle the live round out of the chamber, load another round and it will fire that round, but then repeat the previous steps. I have put one round in the magazine, manually cycled it, fired it and the bolt locked back. I assume that means the gas block and gas pressure is OK. With the lower removed from the upper receiver I can manually lock back the trigger and it seems to function properly.

    I have an Anderson lower with a PSA MPI bolt carrier group. Not sure what the upper is - no distinguishing marks. I am shooting American Eagle 50 gr jacketed hollow points.

    Any ideas would be appreciated.

    Mike
    Click to expand...

    It sounds as if it is short-stroking. Have you tried full-powered 5.56 NATO ammo in it? What gas length does the upper have? Also, what buffer? Full-auto or semi-auto bolt carrier?
     
    Jpyritz

    Jpyritz

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    If it fires a round then bcg travels far enough Back to eject and pick up a new round and chamber it, then to me its not short stroking. If it short stroked then a new round wouldn't be picked up. My guess without looking at it would be a fire control group issue. If by any chance your in the pace area or wanna drive out I'll take a look for. FYI I'm prior infantry and certified gunsmith in and out of the army
     
    FrommerStop

    FrommerStop

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    If the firecontrol group is not functioning correctly there could also be a safety issue, so get it check by someone that knows about ARs; Jpyritz sounds like a good person to see.
     
    FrommerStop

    FrommerStop

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    I see that his fellow lists his location as texas so he will have to find help over there.
     
    Jpyritz

    Jpyritz

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    Correct it could turn your semi- into a full auto and be extremely dangerous if your not expecting it to happen. Like I said I'll take a look free of charge. All I ask is you make the drive.
     
    Jpyritz

    Jpyritz

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    OK well TX is a bit of a drive lmao. If you have 25 bucks to spare buy a palmetto fcg. Too easy to change out. Better be safe and have a functioning rifle then sorry.
     
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