The USAS-12 is a gas-operated, selective-fire weapon which is designed to provide sustained firepower in close-combat scenarios. It accepts detachable 10-round box magazines or 20-round drum magazines. Both types of magazine are made of polymer, and drum magazines have their rear side made from translucent polymer for quick determination of the number of shot shells left. It has an effective range of 40 m.
The latest version of the USAS-12 is capable of fully automatic fire.