Shotguns have wide bores, and long and thin barrels. Shotguns don’t develop a lot of chamber pressure, but the volume of the barrel means that’s a lot of water that needs to be pushed out of the way, and not a lot of material to withstand the pressures that develop.
Both the AK-47 and the handgun shown in this thread have relatively low chamber pressures and short barrels. I’m surprised the AK handles it so easily, though. There’s no chance in hell that I’d try this with a gun firing a full-length cartridge.
