A B-ARFCOM user reported this Kaboom today and there is much discussion on the cause.
I pull the trigger and Kabloooey!!! Shit flying, smoke all over and both thumbs are numb on the pad.
I look down, magazine spring hanging out, follower pieces on the table. I checked myself to see if I was bleeding or missing parts. Nope, but my gun was messed up. The door was bent out and I couldn’t get the bolt to go in or out. Shit, time to go home. I checked my target, and there were 7 holes, just like there should be, so no problem caused by a bullet stuck in the bore.
All pissed off all the way home. Once there I got the bolt/carrier to go back easily by poking it out from the muzzle with a metal rod. The body of the case was still in the chamber. Then took the buffer/stock off and bolt/carrier came right out. Absolutely NO damage to the Aero lower.
The bolt itself has a missing lug and the extractor is bent and chipped. The bottom of the carrier that picks up the new cartridge from the top of the mag is completely blown off like somebody cut it with a knife. You can see the bolt in the channel. Holy shit never seen nothing like it.
The door is wiped out and the bottom of the upper is kind of blown out. I thought possible a broken case in the chamber affected the pressure and blew up my gun. I was looking for a tool to use to pull out the casing. As I flipped it over the case fell right out on the floor. The head has a section missing but the front is just fine and in good shape. I cleaned out the chamber and bore and everything looks just fine.
I honestly thought it was a bore obstruction, but now it looks like I might have a discharge when the bolt was not in battery, like not all the way forward.
That shit really shook me up. My thumbs were numb for an hour, and it took me a few minutes to realize what just happened. If it fired out of battery, how the hell did that happen. All I can think is that the carrier got damaged during the previous (6th)shot. And when I touched off the 7th shot the damaged carrier parts came apart and let it hit the primer before it was in battery.
First time for everything.