AA12 (Auto Assault 12)
Country of origin

United States of America


Military Police Systems


Maxwell Atchisson (Atchisson Assault Shotgun)
Jerry Baber (AA-12)

Weapon type

Automatic shotgun


12 gauge (2.75 inches)


Forced gas-operated blowback, open bolt

Overall length

966 millimeters (38.0315 inches)

Barrel length

457 millimeters (17.9921 inches)


4.76 kg (10.494 pounds)

Weight empty

16 lb (7.3 kg)

Magazine/Cylinder capacity

8-round detachable box magazine
20- or 32-round drum magazine

Cyclic rate

300 RPM[1]

Maximum effective range

75 meters (246.063 feet)

The Auto Assault-12 Automatic Shotgun, or AA-12 for short, is an automatic shotgun originally developed in 1972 as the Atchisson Assault Shotgun by American gun designer Maxwell Atchisson.

The rights of the original prototype were sold to Jerry Baber of Military Police Systems in 1987. In the following years, the design was overhauled until the first prototypes were made public in 2004.[1][2] The current model was released in 2005 after 18 years of development and no less than 188 changes and improvements to the original blueprint.

Design details

The AA-12 is a select-fire, gas-operated shotgun chambered for 12 gauge (the 2.75 inch variation). It can fire a variety of projectiles such as buckshot, flares, slugs, less-than-lethal stun batons and high-explosive FRAG-12 grenade rounds.

The weapon's select-fire functionality allows it to operate in automatic or semi-automatic fire.

It has two types of magazines; the first is a detachable box magazine containing eight cartridges, and the second is a drum with a capacity ranging from twenty to thirty two cartridges.

The AA-12 has a cyclic rate of 300 rounds per minute with a muzzle velocity of 1050 fps.

The original Atchisson Assault Shotgun prototype was constructed from components of other weapons, such as the trigger group of a Browning M1918 B.A.R. and the stock and forearm of an M16.

The AA-12 featured a self-cleaning body made of aerospace-grade stainless steel components that self-lubricates with carbon from the shells' detonation.


  1. 1.0 1.1 Article "Auto Assault 12 (AA12) Combat Shotgun for Mil/LE Special Operations" in Defense Review. (Retrieved September 16th 2014, 17:56 CET)
  2. Article "Atchisson Assault Shotgun" in Wikipedia The free encyclopedia. (Retrieved September 16th 2014, 18:10 CET)