Round "cooking off" in the magazine?

[TomMcC]

Was there an indentation on the primer? If the case was unsupported and went off it seems that rupture would be larger than an 1/8". How did he describe the spent case in the chamber, was it normal?

[pinzgauer]

So I was able to track down the fellow who had this incident. He said that the round in the chamber didn't cook off; one of the rounds in the mag went off. He said that shell casing has a gash about 1/8 inch long perpendicular to the extraction groove. He said it was a reloaded round.

It looks like they've reloaded that shell one too many times.

So it just decided "I'm worn out and wounded... Think I'll blow up"?

Something had to set it off. As in hitting the primer. People tumble live mil surp ammo in concrete mixers... (I don't, but some do)

[MegademiC]

So I was able to track down the fellow who had this incident. He said that the round in the chamber didn't cook off; one of the rounds in the mag went off. He said that shell casing has a gash about 1/8 inch long perpendicular to the extraction groove. He said it was a reloaded round.

It looks like they've reloaded that shell one too many times.

Are you saying a round in the mag fired while in the magazine?
I really dont think that happened- or did I misunderstand? How would it have an extraction groove?

[AKDoug]

He had a ruptured case and the gas blew out the mag. That's how it's supposed to work.

[ryder021970]

Was there an indentation on the primer? If the case was unsupported and went off it seems that rupture would be larger than an 1/8". How did he describe the spent case in the chamber, was it normal?

Both shooter and RO said that as the bolt closed on the round, this "explosion" happened. Everything blew out through the floorplate. The round in the chamber was unfired....(??)

[ryder021970]

Most of the comments here say that this is a ruptured case. Maybe that is what happened; there also could have been a sharp thing in the mag ( I dont know ) that may have hit the primer....

[Iraqgunz]

An AR cannot fire out of battery. The hammer cannot strike the firing pin, and out of battery means the firing pin cannot protrude through the bolt face and contact the primer.

[MegademiC]

Well, now it sounds like a slam fire? Could the primer have blown out and caused this?

[TomMcC]

But he's saying that the round in the chamber was unfired.

OP, was there a ruptured case at all as a result of the mag blowing? An 1/8" slit near the ejection groove of the case from the mag doesn't seem sufficient to cause what is being described.

And in the end we're probably never going to know what really happened. If a cartridge actually was detonated IN the mag, it's the first one I've ever heard of.

[P2000]

Maybe the round in the mag with the split case had the split case already before the incident. Real shitty reload. So it was spilling powder everywhere or at least had exposed powder. Sometimes some Sparks and flame get into the upper receiver while firing. This could set off this round with little damage to anything.
Without pics it's all just speculation, but this is the only way that a round going off in the mag seems possible. There is no way a round cooks off in an ar mag, that is ridiculous.