Originally developed by Maxwell Atchisson during his tenure at the Military Armaments Corporation in the early 1970s, the production rights were eventually sold to Jerry Baber of Military Police Systems in 1987. Baber made modifications to the design and released his improved model in 2004. In 2005, it finally entered production, after 18 years of development and no less than 188 changes and improvements to the original blueprint.
The AA-12 is a fully automatic, gas-operated API blowback shotgun chambered for 2¾ inch 12 gauge shells. It can fire a variety of projectiles such as buckshot, flares, slugs, less-than-lethal stun batons and high-explosive FRAG-12 grenade rounds.
It uses two types of magazines; the first is a detachable box magazine that contains eight rounds, and the second is a drum with a capacity ranging from twenty to thirty-two rounds.
The AA-12 has a cyclic rate of 300 rounds per minute with a muzzle velocity of 1050 fps. Its slow rate of fire makes single-shots or bursts very easy to achieve through brief trigger pulls, despite the fact that it fires in full-auto only.
The original Atchisson Assault Shotgun prototype was constructed with a variety of components from other weapons, such as the trigger group of a Browning M1918 B.A.R. and the stock and handguard of an M16A1.
The AA-12 featured a self-cleaning body made of aerospace-grade stainless steel components that self-lubricates with carbon from the shells' detonation.
- BC Jaeger: A semi-automatic version of the AA-12 built by BC Engineering of Tennessee. In May of 2016, BC announced that they have interest in selling the rights to manufacture the shotgun for civilian usage.
- Sol Invictus AA-12: A version of the AA-12 built by Sol Invictus Arms of Florida. Currently marketed as a semi-automatic civilian firearm, a fully-automatic version appears to be under development.
- Article "Auto Assault 12 (AA12) Combat Shotgun for Mil/LE Special Operations" in Defense Review. http://www.defensereview.com/auto-assault-12-aa12-combat-shotgun-for-mille-special-operations/ (Retrieved September 16th 2014, 17:56 CET)
- Article "Atchisson Assault Shotgun" in Wikipedia The free encyclopedia. https://en.wikipedia.org/wiki/Atchisson_Assault_Shotgun (Retrieved September 16th 2014, 18:10 CET)
- Article "BREAKING: Is the Atchisson AA-12 Fully Automatic Shotgun Up for Sale!?" in The Firearm Blog. https://www.thefirearmblog.com/blog/2016/06/25/breaking-atchisson-aa-12-fully-automatic-shotgun-sale/ (Retrieved July 14th, 2018, 19:37 EDT)