Round "cooking off" in the magazine?

[ryder021970]

A few weekends ago I was at the local range and some guys were in the other bay shooting AR's. One of them came up to the line and started firing.

As he squeezed off a round, his magazine floorplate was blown out and the remaining rounds, follower and spring was dumped out. the RO immediately commanded him to stop and they went through the clearing process etc.

It was though that a round cooked off in the magazine; others thought something sharp probably hit the primer, setting off the round.

No injury to anyone and the magazine was re-assembled without any apparent damage.

What do you think happened?

[vicious_cb]

Kabooms will follow the path of least resistance which is down the magwell and out the bottom of the magazine. Sounds like a normal kaboom to me, nothing special.

Also setting off a round outside the chamber is pretty unimpressive, its just a big firecracker.

[cctroupe11]

Sounds more like the weapon fired out of battery.

[1168]

Cb and Troupe are on point.

[seb5]

It appears to me that he didn't reassemble his magazine properly and firing the weapon launched the floor plate. If a round went off while in the magazine there would be damage, at least to the magazine, possibly the lower as well. Of course a round being ignited without a chamber doesn't generate any real velocity. Or it did fire out of battery? In the two cases over the years of seeing this there was evidence of it happening.

[ryder021970]

Thanks for the inputs, guys.

If it fired out of battery, would the bolt carrier still be able to extract and eject the shell casing? Unfortunately, I didn't see if it did.

I saw the magazine; I didn't see any damage to it so it.

[AKDoug]

Sounds more like the weapon fired out of battery.

How does an AR fire out of battery?

[Rifleman_04]

How does an AR fire out of battery?

It didn’t.


The AR can not fire out of battery.

[cctroupe11]

It didn’t.


The AR can not fire out of battery.

If the bolt is out of spec or the headspace is improperly set, an OOB detonation is completely possible resulting in a case head separation, blowing out the magazine and (sometimes) destroying the upper reciever. I have seen it happen.

[jack crab]

Something similar happened to me with Canadian milsurp rounds. Round fired in battery. Way over pressure. Blew the bottom of the bolt carrier down through the magazine with all the rounds, spring, follower, floorplate, etc. The top of the bolt carrier had a longitudinal crack so that the key for the gas tube and the bolts just fell out when I finally got the upper apart. The upper receiver bowed out at the ejection port and bent the dust cover and rod.

Needless to say but that pretty much ended the day.