AA12 (Auto Assault 12)
Country of origin



Military Police Systems


Maxwell Atchisson (Atchisson Assault Shotgun)
Jerry Baber (AA12)

Weapon type

Automatic Military Shotgun


12 gauge (2.75 inches)


Forced gas-operated blowback

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
8-, 20-, or 32-round drum

Cyclic rate

300 rounds per minute[1]

Maximum effective range

75 meters (246.063 feet)

The Auto Assault 12 Automatic Shotgun, or AA12 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 first prototypes were made public in 2004.[1][2] The current model, known as the MPS AA-12, was released in 2005.

Design details

The AA12 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 and HE 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 AA12 has a rate of fire of 300 rounds per minute with a muzzle velocity of 1050 fps.


  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)

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