Pancor Jackhammer

The Pancor Corporation Jackhammer is a 12-gauge, blow-forward gas-operated bullpup automatic shotgun designed by John A. Anderson in 1984 and patented in 1987. Only three working prototypes of the Jackhammer were built, but despite notable interest, legal and financial difficulties meant the Jackhammer never entered production, though it was notably popular as a prop weapon in films, television shows, and video games in the 1990s and 2000s, owing to its futuristic design and unusual operation.
A Korean War veteran, Anderson had problems with the slow reloading process of the pump action shotguns he used during his service, leading him to attempt a shotgun design without this drawback. There were reportedly several foreign governments that expressed interest in Anderson's design, with initial production units being ordered, however the design was eventually rejected after testing.
The weapon features a 10-round cylinder behind the trigger, using a similar mechanism for rotation as seen in the Webley–Fosbery revolver. These cylinders were also designed to be used as a device akin to land mines, known as a 'Bear Trap'. Designed to contain the pressure of firing, these cylinders could...