I've had a Mega lower built & ready for the carbine upper to be assembled after the DAY.  I just couldn't wait.  I bought a complete 20" Oly post ban upper that snuck in under the ebay police radar.  Slapped it together & went to the backyard range to give it a whirl.  The mag seated fine & the first five rounds worked perfectly.  I handed the rifle to my son's friend Mike, age 17, to give it a try.....grin factor +12  He'd never fired an AR before...hooked another one  The kid did great, five shots @ 100yd, he hit 4 steel targets & one plastic milk jug firing off hand.



I reloaded the mag & went about a little more trigger pullin'.   First round fired and then it jammed WTF??  Initial field exam was that perhaps two rounds stripped out of the mag & stuck in the chamber.



After disassembly back on the bench I discovered a ruptured case...whew.  No KB. No sign of damage.



It was a reloaded case with a NATO mark on the base.  I'll list that failure as "shithappens"