The USAS-12 was developed in South Korea and was intended as a special purpose, military or special operations close combat weapon with extreme firepower. USAS-12 is a gas-operated, selective-fire weapon which bears a certain resemblance to the M16 assault rifle and uses clever design for relatively low peak recoil and low rate of fire, which is essential for firing powerful 12 gauge shells. The 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. It uses large 10/20 drums and has a polymer buttstock. Post type, hooded front sight an adjustable rear sight built into the carrying handle, similar to one found on M16 assault rifles.

On the downside the USAS-12 is very bulky and heavy, but the large mass greatly improves the recoil control, especially in full automatic (bursts) mode.