I was at my LGS today and the prop showed me this:
click to embiggen
This used to be a Wilson Combat AR in 5.56. The owner was just minding his own bidness, shooting some Aguila factory loads when this happened. It's not a swell photo because I just clicked off a couple of shots and didn't check them for quality but I left it oversized so you still can make out the two biggest
Uh-Ohs.
You can see that the bottom of the BCG is blown out like a partially peeled banana. And the
billet receiver is fractured at the rear. I figure the fracture had to be either from an overpressure or the BCG slamming into something rigid at full recoil but I didn't see anything in the wreckage that might indicate which, but I'm pretty sure that piece is stout enough to drive a Mack truck over it with no more than cosmetic damage.
What you can't see is that the BCG is frozen solid. The bolt is unlocked but still in the breech. The dust cover is warped, bowed outwards slightly at either end. There are no "witness marks" on the face of the recoil buffer. And if you stick a cleaning rod down the bore you'll find the barrel is obsctructed about two inches and a bit forward of the breech. Meaning there probably is still a live round in the chamber.
And damned if I can piece together a sequence of events that would make it possible for all that damage to occur but end up with a fresh round in the chamber.