The Atchisson Assault Shotgun was developed by Maxwell Atchisson in 1972. The shotgun served as the template for several later weapons, especially the USAS-12 combat shotgun.
The shotguns direct successor is the AA-12 selective fired shotgun. This shotgun was featured on Future Weapons on March 19, 2007.
Max Atchisson, in 1987 sold his rights in the AA-12 to Jerry Baber of Military Police Systems, Inc. Baber's company effectively produced and developed the next generation of the assault shotgun called the Auto Assault-12.
This weapon was redesigned with 188 improvements and changes from the original blueprint, and the weapon had taken about 18 years to fully develop. The MPS additionally teamed up with Special Cartirdge Company and Action Manufacturing Company to join the gun with FRAG-12 High-Explosive ammunition into the advanced weapons system. In 2004, 10 firing models of the weapon of the Assault Shotgun 12 were produced, and were shown to United States Marine Corps.
The shotgun is shortened 966 mm however retains some barrel length as the original as well as lightened to 4.76kg. The shotgun utilizes an eight round box magazine, 20 round drum magazine, or 40 round drum magazine. The weapon is designed and manufactured to fire three different twelve gauge shells: Slugs, Buckshot or Frag-12. The MPS also has been stated by the company to require zero lubrication or cleaning.
The Atchisson Assault CQB model comes with a 13 inch barrel length and is weighted a half pound lighter than the regular model.