XM174 Grenade Launcher
In the early 1960s American advisers in Vietnam requested an automatic grenade launcher which could act as a force multiplier. The US Army responded in September 1963, by calling on private industry to submit designs for a low velocity 40mm automatic grenade launcher. The new launcher had to weight below 12lbs and feed from a belt. Four competing companies submitted designs with the entry from the Aerojet Ordnance Manufacturing Company tentatively selected in February 1964.
Throughout 1965 Aerojet worked up their design and with feedback from the Army altered it to fire from a closed rather than open bolt and a sem-automatic fire capability. The weapon was initially designed to fire from a tripod but the Ordnance Corps also requested a design with a buttstock which could fire from a bipod. The weapons sights were taken from the shoulder-fired, single shot M79. It appears that the general shape of the XM174′s receiver and pistol grip were styled after the M1919 medium machine gun, possibly for the sake of user familiarity.
Designated the ‘Launcher Grenade 40MM Low Velocity Automatic, XM174′, Aerojet continued development throughout 1966 with the assistance and oversight of Springfield Armory and Rock Island Arsenal. It was initially envisaged that the new grenade launcher would be vehicle and tripod mounted but weighing under 12lbs, less than half the M60 light machine gun, the Army quickly saw hip-fire potential in the XM174.
Despite being lighter than an M60, the XM174 proved to be less ergonomic and more difficult to carry in the field. Aerojet developed a 12-round drum to carry the weapon’s belt to ease carrying and loading on the move. When field tested in Vietnam the drum magazine was found to be fragile and suffered a high attrition rate. Units from all three services tested the XM174 in Vietnam. Including Air Force base security units, the 1st Battalion, 27th Infantry Division and the USMC. In the photograph above we can see Major Joseph Flynn, 26th Marine Regiment, explaining the specific features of the XM174 to a group of generals in October 1969.
While the XM174 suffered teething problems in the field including issues with the drum system, poor ergonomics and complaints about its effective range. In the meantime Naval Ordnance Station Louisville had developed the Mk19 in 1968. The Mk19 was quickly adopted for vehicle and tripod mounted use by the Marine Corps and Army and the Ordnance Corps abandoned the XM174, some continued to be used in Vietnam into the early 1970s. Troops at squad level continued to use the M79, XM148 and the M203.