AR-15 failure

[Hecklerusp45]

I was at the range shooting a Garand when an older gentleman started shooting his Rock River AR-15. He fired for a while then ran into a problem. The rifle would chamber a round but it would not fire. I looked at a couple of the rounds and could see a light firing pin mark on the primer but no more of a mark then should be expected when a round is chambered. I opened the rifle up and pulled the bolt/bolt carriage out and found that the buffer retainer and its spring had come loose and had been “run over” by the bolt. I don’t even know what is supposed to hold the retainer in place so I was wondering how one would come out like that. Any thoughts?

[bonnie]

Lip of buffer tube. Not properly installed.

[Col. Colt]

Yup! Buffer tube probably one turn short of being fully screwed in. Other option would be an improperly machined "reciever extension" (AKA buffer tube) lip or too large a hole in the reciever for the retainer and spring - both unlikely. CC

[Hecklerusp45]

Thanks for the info guys. Nice to have some "pros" around to answer questions.

[cnjcomp]

Check to see if there is too much lube in the bolt/carrier group. Had one shooter at my range that had a hydraulic problem with the firing pin. After removing so of the oil. It functioned just fine.

[joem]

Friend of mine had AR15 problem where it wouldn't fire. His cousin had same problem on his. I took it apart and the bolt carrier and bolt needed cleaning real bad. had him clean it while I watched and made sure he knew how to do it in the future. Also gas rings completly worn out which I replaced for him.