I had an M1 fire out of battery during a match and catastrophically fail. Bolt was driven into the rear of the receiver, blowing the back of it off at the serial number and a big chunk out of the stock.
Ammo was factory/issue LC 69.
Lucky for me, it happened during the slow fire prone string and the gun wasnt in my shoulder when it went. If it had happened during the rapid fire strings, I probably would have got that piece of receiver in my head.
Scary thing is, Id got a couple of "doubles" in those rapid fire strings and thought it was just me, as the gun was new (new to me, it was a DCM gun Id just got) and I might have milked the trigger, which isnt uncommon with M1's, although I never really had the issue before. When my brass was recovered later, there were a couple of pieces with the necks blown out, so it was happening prior to it cutting loose.
I walked away with a nice "L" shaped tear and a half dozen stitches in the palm of my hand, the base of the case burned into it as well, and some hearing loss.