Any guess what caused this? Hard to tell from the pics

[Joe504]

http://www.thetruthaboutguns.com/2014/08/daniel-zimmerman/shotguns-ammo-go-boom/

[youngmman]

Either a double charge shell or ,more likely, a shell one or two gauges smaller lodged in the barrel then a correct gauge shell fired, ie,
a 20 g shell lodged in a 12 g barrel then a 12 g shell fired. NAAAAAAAAAAAAAAAAAAAAAASTY!

[ksfowler166]

The guy posted this on SGW. http://www.shotgunworld.com/bbs/viewtopic.php?f=2&t=404175 Perhaps it was a failure of the mono block on the shotgun not the ammo. I doubt it was the shell since it takes some serious pressure to destroy an action. I have seen where a 20ga shell was put in a 12ga and a 12ga shell was put in after and it did not look anything like what happened to that Fausti. What that Fausti looks most like is when a couple of guys took a standard 12ga factory target load and removed the cushion section on the wad plus they brought the shot weight up to 2oz+. Even then it was not nearly as bad as the Fausti. So something seriously wrong must have happened to get that type of damage.

[FullTang]

I would agree that it's hard to blow things up like this with your basic double-charge. Seems like you'd need a double charge of powder, plus an extra-large payload of shot, and there just isn't room for all that stuff in the hull (not with a wad, anyway.) This reminds me of the Vietnam stories of guys sabotaging captured AK rounds by dumping out the powder and filling the cases with C4. They'd put them back into AK47s and leave them out on the trail somewhere. When the VC scooped them up and tried to use them---kaboom!

Could have been a cracked chamber, or similar failure---that does seem most likely, but sabotage is always on the list!