I just got my first AR last week and I'm having some problems with her. I ran two mags through it just fine this morning then decided to try a round of silver bear to see if it would cycle...well it didn't as happened before so I started to tear it down to clear the casing. When I took the upper off I realized I forgot to put the bolt forward so the buffer just slammed forward/out. Since then the buffer retainer keeps coming out and the gun failed to fire the next two rounds I tried.

I tried putting one more turn on the stock to hold the pin in there but then that prevents the upper from seating properly.

This is a DPMS lower, some kind of A3 upper, and a collapsable stock.

Thanks for all the help yall have already provided me on here and I appreciate any input on this, Thanks!

Time to break out the file and do some tuning.

Bottom of receiver extension lip should be just short of touching the center post of the buffer retaining pin (over the top of the outer lip), and the top of the tube should be just flush with the lower receiver thread section when the butt stock is indexed/installed correctly.

I filed the stock down and it holds the retainer pin in properly now. I'll find out Tuesday if that also solves the problem of the gun not firing. I suspect the retainer pin got loose in there and kept the hammer from hitting the firing pin.

Thanks for the help!