Last night I happened to see a myth Busters episode where they were plugging the barrel of a 12 gauge and firing it.They were trying to see if the barrel would peel like a banana like in the Elmer Fudd cartoons. They started out with a fake hand in front of the muzzle goodbye hand, Then they pushed the muzzle 6 inches into the ground, this time they got a slight bulge in the barrel but the ventilated rib peeled right back, the last thing they did was plug the barrel with a round piece of steel about 6 inches long, they also welded this to the barrel. When they fired the gun the plug was blown out of the muzzle, and a small bulge was in the tube, I was really surprised. There was no backblast that would have harmed the shooter. But I wouldn't pull the trigger on something like that. I remember a video that was making the rounds where an elk hunter had his barrel peel back when he fired with an obstruction in the barrel.