The USAS-12 automatic shotgun is a gas-operated, select fire Tau'ri combat shotgun. The weapon has primarily been used to fight the Replicators. It is typically found in Stargate Command's service fitted with 20-round drums. It resembles an over-grown Colt M16A3 rifle and—except for the charging handle—has its controls in the same locations.
This weapon was employed on the initial excursion to Chulak. Later, SG-1 used the USAS-12 when Thor requested Col. O'Neill's help defending his ship from replicators. Stargate Command continues to employ these weapons whenever Replicators are encountered because the firepower available from the design is effective. (SG1: "Children of the Gods", "Nemesis", "Menace", "Reckoning, Part 2", "The Ark of Truth")