The XM174 is a mounted automatic 40 mm grenade launcher heavily based on the M1919A4 machine gun and the M79 grenade launcher, but fed from an ammo can.

[1] It was used in the Vietnam War as a tripod mounted crew-served weapon and as a weapon mounted on various vehicles and aircraft.

[2] The ammunition was held in a drum canister with a maximum capacity of twelve 40 mm rounds.

The launcher was also capable of semi-automatic fire.

U.S. Air Force Security Police personnel in Vietnam were also issued the XM174 automatic grenade launcher which was often used on perimeter defense posts and heavy weapons vehicles.