The Heckler & Koch HK CAWS (H&K CAWS) is a prototype automatic shotgun co-produced by Heckler & Koch and Winchester/Olin during the 1980s. It was Heckler & Koch's entry in to the U.S. military's Close Assault Weapon System program.
The CAWS program started in the early 1980s in the United States. The main goal of this program was to develop a new generation personal firearm, capable of firing high-impulse, multiple projectiles with effective range of 100–150 meters.
One of the teams entered in the CAWS competition was Heckler & Koch Germany, coupled with Winchester-Olin. Heckler & Koch was responsible for developing a firearm, while Winchester-Olin was responsible for the development of new types of ammunition suitable to fire in it. Although tested by the U.S. military, the CAWS program was canceled, and production of the weapon, both military and civilian, has halted.
The Heckler & Koch CAWS is a select-fire, recoil-operated bullpup shotgun, with three modes of fire: SAFE, SEMI, and AUTO (S-1-F). It is chambered for 12 gauge shotgun shells and features a 10-round detachable box magazine. However, rather than using standard 12 gauge ammunition, the CAWS was designed around a belted case shell that fired tungsten alloy buckshot. The CAWS ammunition is incompatible with standard 12 gauge weapons as a result of much higher gas pressures and different case geometry.
The CAWS came in several different barrel lengths, varying between 457mm (approximately 18 inches) and 685mm (approximately 33 inches). Certain prototypes came equipped with a foregrip.