what caused it?

[Bennyboy]

I agree with some of the posts there that it looks like it fired at least partially out of battery.

 

[Timber Cruiser]

Cut shell?

 

[trw2094]

Been there and done that, apparently that's not the case on this one though. Looks like overcharged hand loads , maybe.

would a double charge in a shotshell even allow the wad and shot to fit in it?
Would a double charge be enough to explode and shotgun?
I would say a barrel obstruction, 20 gauge shell maybe.

 

[Horsehat]

Pressure in excess of the design parameters.

 

[Dan Muk]

I had my CZ 712 Grenade on my buddy when he borrowed it for a skeet shoot. Firing pin was found to be stuck in the bolt in the forward position causing it to go KABOOM out of battery. My buddy escaped with a few scratches and a bruised hand. CZ gave me a brand new shotgun and I gave it to my friend who almost lost his hand. I’m pretty sure he never shot it and traded it off because he was so jaded from that experience!

 

[Gimmebackmybullets]

Im betting that somewhere between the gun leaving the factory and the day this happened, there was an irresponsible dumb ass involved.

 

[Toothlesswun]

would a double charge in a shotshell even allow the wad and shot to fit in it?
Would a double charge be enough to explode and shotgun?
I would say a barrel obstruction, 20 gauge shell maybe.

No idea on the double charge, but I do know for a fact, a 20 in and a 12 on top with a trigger pull will kill an A5 in the same way