USAS-12 shotgun was developed in South Korea by Daewoo Precision Industries somewhere in the 1980s, and according to some sources, its design is based on experimental Atchisson Assault Shotgun, developed in 1970s in USA by someone Maxwell Atchisson. USAS-12 was intended as a special purpose, military or special operations close combat weapon with extreme firepower. It was exported from South Korea in many countries, including the USA, but in 1994 under the new US law it was classified as a Class III "Destructive device", which limited its civilian sales and use. It is still offered for military and law enforcement agencies, though.
USAS-12 is a gas operated, selective fire weapon. It uses a gas system located above the barrel, with more or less conventional rotating bolt locking. The interesting feature, probably borrowed from Atchisson designs, is the long bolt overtravel, which results in relatively low peak recoil and low rate of fire, which is essential for weapon firing powerful 12 gauge shells. USAS-12 is an ambidextrous weapon, having two ejection ports on each side of the receiver, and two slots on the forearm for cocking handle. The ejector on the bolt and the cocking handle could be easily set to operate either side of the gun, depending on the present shooter needs and preferences. USAS-12 is feed from large capacity box or drum magazines, holding 10 and 20 rounds respectively (there are some sources that indicate that earlier versions of the USAS-12 were imported into USA with 12 and 28 rounds magazines). The polymer buttstock is hollow and is used as a space for bolt group to recoil, so the folding butt version is unavailable for this design. USAS-12 has a post type, hooded front sight at the top of the gas chamber and an adjustable rear sight built into the carrying handle, similar to one found on M16 assault rifles.
USAS-12 is very bulky and heavy, but the large mass greatly improves the recoil control, especially in full automatic (bursts) mode.
gas operated semi-auto (select-fire version exists)
12 Gauge (2 3/4 in shells - 70 mm chamber)
(Loaded/Unloaded) 6.2 kg w/10 rounds / 5.5 kg empty
10 rounds box or 20 rounds drum detachable magazines