Pancor Jackhammer Internet Movie Firearms Database ...
The Jackhammer is a bullpup automatic shotgun which never entered production, using a revolverstyle detachable cylinder (referred to as a "cassette") with a rotating action similar to the British WebleyFosbery Automatic Revolver, and a gasseal system similar to that of the Nagant Revolver, though with the barrel moving back to form the seal instead of the cylinder moving forward.