That would either be an elephant gun or some sort of custom double mounted SPAS. But neither of those shotguns are particularly good at blowing chunks out of things...
The best for doing that is the Remington Wingmaster: US Special Forces Standard Issue Combat Shotgun...
It is designed to be increadably responsive with a wide spreadshot, so that if the user is ever startled by an enemy, he can quietly and efficiently passify the situation by blowing a MASSIVE hole in him.
Not only does it sound like a razor blade, but it cuts like one too
Reese