This video shows the aftermath of some faulty Wolf ammunition. A Mossberg 930 SPX was running Wolf slugs when one of the rounds squibbed. A “squib” is when the primer goes off but not the full charge and propels the projectile into the barrel but not out the muzzle, meaning the barrel is obstructed. The shooter did the usual malfunction drill and racked a new slug into the chamber, then fired. The pressure caused by the two projectiles in the barrel made the barrel rupture and split open. Wolf ammunition has since offered to refund the shooter for the ammo as well as pay for the repairs to the shotgun, but I don’t think I would ever trust a gun that has been fixed after an accident like that.
Moral of the story: If your gun goes “click,” check the cartridge to ensure it’s not a squib.