Atchisson Assault Shotgun
The Auto Assault-12 originally designed and known as the Atchisson Assault Shotgun, is a shotgun
A shotgun is a firearm that is usually designed to be fired from the shoulder, which uses the energy of a fixed shell to fire a number of small spherical pellets called shot, or a solid projectile called a slug...

 developed in 1972 by Maxwell Atchisson. The current 2005 version has been developed over 18 years since the patent was sold to Military Police Systems, Inc. The original design was the basis of several later weapons, including the USAS-12
The Daewoo Precision Industries USAS-12 is an automatic shotgun designed as a combat shotgun manufactured in South Korea by Daewoo Precision Industries during the 1980s.- Design :...

 combat shotgun. The weapon is selective fire
Selective fire
A selective fire firearm has at least one semi‚Äďautomatic and one automatic mode, which is activated by means of a selector which varies depending on the weapon's design. Some selective fire weapons utilize burst fire mechanisms to limit the maximum or total number of shots fired automatically in...

, operating as a semi-automatic
Semi-automatic may refer to:* A semi-automatic firearm, a firearm which automatically reloads, but will only fire one round per trigger pull** Semi-automatic rifle** Semi-automatic pistol** Semi-automatic shotgun...

, or in fully automatic
Automatic firearm
An automatic firearm is a firearm that loads another round mechanically after the first round has been fired.The term can be used to refer to semi-automatic firearms, which fire one shot per single pull of the trigger , or fully automatic firearms, which will continue to load and fire ammunition...

 mode at 300 rounds per minute. It is fed from either an 8-shell box magazine, or a 20- or 32-shell drum magazine.


In 1987, Max Atchisson sold the rights of AA-12 to Jerry Baber of Military Police Systems, Inc., Piney Flats, Tennessee. MPS in turn developed the successor simply known as Auto Assault-12, which was redesigned over a period of 18 years with 188 changes and improvements to the original blueprint. MPS also teamed up with Action Manufacturing Company, and Special Cartridge Company to combine the gun with FRAG-12 High-Explosive ammunition into a multifunction weapon system.

The weapon was lightened to 4.76 kg (10.5 lb) and shortened to 966 mm (38 in) but retained the same barrel length. The CQB model has a 13-inch barrel, and is half a pound lighter than the regular model. Uncommon in other automatic shotguns, the AA-12 fires from an open bolt
Open bolt
A semi or full automatic firearm is said to fire from an open bolt if, when ready to fire, the bolt and working parts are held to the rear. When the trigger is pulled the bolt goes forward, feeding a round from the magazine into the chamber and firing it...

, a feature more commonly found in submachine guns and heavy and squad level machine guns. It uses 8-round box, 20-round drum, or 32-round drum magazines, as opposed to the original 5-round box magazine. Due to the abundant use of stainless steel and the designed clearance for fouling, MPS has claimed that the weapon requires zero cleaning or lubrication. The designer states that cleaning is required after 10,000 rounds.


The AA-12 can use different types of 3" 12 gauge ammunition such as buckshot, slugs
Shotgun slug
A shotgun slug is a heavy lead projectile, that may have pre-cut rifling, intended for use in a shotgun and often used for hunting large game. The first effective shotgun slug was introduced by Wilhelm Brenneke in 1898, and his design remains in use today...

, or less-than-lethal rubber stun batons. Like most 12 gauge shotguns it can also fire flares or special Frag-12 19 mm fin-stabilized HE, HEAP, and sensor fused HEAB "air-burst" fragmentation shells that can detonate in mid-air.


In 2004, ten firing models of the AA-12 were produced and demonstrated to the United States Marine Corps
United States Marine Corps
The United States Marine Corps is a branch of the United States Armed Forces responsible for providing power projection from the sea, using the mobility of the United States Navy to deliver combined-arms task forces rapidly. It is one of seven uniformed services of the United States...


The HAMMER unmanned defense system by More Industries uses dual-mounted AA-12s on the H2X-40 Turret.
Neural Robotics has also mounted the weapon on their AutoCopter Unmanned aerial vehicle
Unmanned aerial vehicle
An unmanned aerial vehicle , also known as a unmanned aircraft system , remotely piloted aircraft or unmanned aircraft, is a machine which functions either by the remote control of a navigator or pilot or autonomously, that is, as a self-directing entity...


See also

  • Automatic shotgun
    Automatic shotgun
    An automatic shotgun is a form of shotgun that is able to fire cartridges continuously while the trigger is pressed, unlike semi-automatic weapons which require the user to depress the trigger for each projectile fired.- Design :...

  • Combat shotgun
    Combat shotgun
    A combat shotgun is a shotgun that is intended for use in an offensive role, typically by a military force. The earliest shotguns specifically designed for combat were the trench guns or trench shotguns issued in World War I...

  • Daewoo USAS-12
  • List of shotguns
  • Military technology and equipment
  • Saiga-12
    The Saiga-12 is a Kalashnikov-pattern 12 gauge combat shotgun available in a wide range of configurations. Like the Kalashnikov rifle variants, it is a rotating bolt, gas-operated gun that feeds from a box magazine...

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