The United States Atchisson Assault Combat shotgun – Auto Assault-12 or AA-12 or MPS AA-12 - was originally designed in 1972 by Maxwell Atchisson.  This shotgun features selective firing which allows it to operate as a semi or fully-automatic weapon.


The Armed Forces History Museum in Largo, FL has an incredible collection of Firearms and Ordnance in the museum.  The room houses a wide range of history dating back to the Revolutionary War.  This gallery awes visitors as they realize the history and the power encased within. 



Though the original design for this weapon was the creation of Maxwell Atchisson, the 2005 version is the result of 18 years of further development and 188 blueprint changes by the Military Police Systems, Inc. (MPS) after purchasing the rights for this shotgun from Atchisson in 1987.



The result was a lighter weapon which was overall shortened without altering the barrel length.  Not usually found on an automatic shotgun, the newer designed AA-12 actually fires from an open bolt.  Additional improvements made by MPS minimize the need for cleaning and lubricating the shotgun.

Additional Features

  • Pistol grip
  • Shoulder stock
  • Easy-sighting system
  • Uses 3 inch 12-gauge ammo including Buckshot/Slugs/Rubber Stun Batons/Flares
  • Feed System – 10-round detachable box magazine (or) 20-round or 32-round ammo drum
  • Firing Pin built into the bolt
  • Muzzle extension provided for door-breaching making it the preferred shotgun of infantry units in Afghanistan and Iraq.



  • Cartridge:  12-Gauge
  • Action:  API Blowback
  • Rate of Fire:  300 rounds/minute
  • Muzzle Velocity:  1,100 feet per second
  • Effective Range for 12-gauge slug:  325+ feet
  • Maximum Range w/FRAG-12 ammo:  660 feet


Known as a ‘point-and-shoot’ weapon, the AA-12 can stand up to just about any climate or condition and is capable of being fired even when upside down. The United States Atchisson Assault Combat Shotgun is a well-built weapon known for its durability and dependability and in 2004 was demonstrated to the USMC who was considering purchasing the shotgun.