Serious issue with new build. HELP !

[Country Boy]

I just "finished" my first build. DPMS LR .308. Unfortunately, when I went to shoot it,I had a serious issue. 1st. I shot several rounds one shot at a time.No problem. 2nd. I began to rapid fire. After about 6 shots the rifle jammed with one round stuck half way into the chamber being held solid by the bolt carrier group. Wound up taking rifle apart and found that the Buffer Retainer and Buffer Retainer Spring had jumped out of their original position. The Retainer was jammed between barrel and Bolt Carrier Group. Retainer was bent and scuffed.The Retainer Spring was bent and twisted and was laying on top of the  trigger assembly. I have ordered new Buffer and Spring. My question is WHAT WENT WRONG and HOW DO I FIX IT. I would appreciate any help/advice. Thanks

[dpete]

Was the buffer tube threaded into the lower far enough that the bottom edge of the opening held the buffer retainer in?  If it was there should be no way for the retainer and spring to jump out of their socket.

[dpete]

http://s142.photobucket.com/user/_bullseye_/media/IMG_2498.jpg.html

Not my picture but shows what I am talking about.

[shepp]

Country welcome to the forum feel free to tell us about yourself in the intro section

[DNP]

I did that with my very first AR I assembled back around 99/2000. Didn't have much of a help base back then and I was completely new to the platform. Mine happened on the very first shot, and then it clicked. That part got replaced, tube installed properly over. No problems since. 

[beantown]

1 hour ago, dpete said:

Was the buffer tube threaded into the lower far enough that the bottom edge of the opening held the buffer retainer in?  If it was there should be no way for the retainer and spring to jump out of their socket.

Spot on dpete. It cannot come out if the buffer tube is threaded in far enough. If it was threaded in far enough, what the heck happened?

[DNP]

What stock was on it?  If something wasn't tight, the tube could have walked back enough to let it fly. When the bolt carrier went over it it shout up into it and went for a ride. Mine was straight up installed wrong. One shot, bang, ripped the tip off the retainer.