The AA-12 was first invented in 1972 by Maxwell Atchisson as the Atchisson Assault Shotgun, but the early versions had problems with reliability and polymer fouling from the plastic hulls of shotgun shells. In 1987, the design was sold to Jerry Baber of Military Police Systems, who rebranded it with its familiar “AA-12” name; then in the early 1990s German-born Boje Cornils was hired on to help improve the design and create the tooling to mass produce it. By the early 2000s, the design had been substantially improved, including a complete aesthetic overhaul thanks to an external two-piece polymer shell.
In 2004, the design was demonstrated to the US Marine Corps, which substantially raised its popular profile. In 2005, SOF Magazine floated the idea of combining the AA-12 with a new type of ammunition: The Quantico-developed FRAG-12 explosive shaped charge 12 gauge shotgun round. The AA-12 is designed for military use, and can survive below zero temperatures or a dunk in salt water thanks to its stainless steel construction. It uses a Tommy-Gun like cylinder to feed in the cartrides and is designed to operate with almost no recoil.