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Developed in the 1950s and entering service in 1961 to replace rifle grenades as an infantry platoon support weapon, the M79 single-shot grenade launcher looks like a large-bore sawed-off shotgun and fires a 40 mm grenade.

The gun employs the “high-low propulsion system” developed by the Germans in World War II. The round burns its propellant charge within a small high-pressure chamber. The pressure then bleeds through small holes into a larger low-pressure chamber to launch the round through the barrel. That system reduces the recoil forces, enabling the M79 to fire grenades containing 2.5 ounces of high explosives, tear gas, pellets or smoke agents.  

Two types of fuses are used: the M552, which arms 3 meters (3 yards) from the muzzle; and the M551, arming 14 to 28 meters (15 to 30 yards) from the muzzle. The high-explosive round has an effective casualty radius of 5 meters (5 yards). Vietnam’s close-range engagements led to development of the canister, or “buckshot,” round that propelled 20 to 27 pellets to about 30 meters (32 yards).

More accurate, powerful and longer-ranged than rifle grenades, the M79 was popular with U.S. and allied troops, who called it Thumper or Bloop Tube. The gun has a blade sight on the barrel’s tip and a folding-leaf rear sight that can be adjusted for windage or range—in increments of 25 meters (27 yards) out to 375 meters (400 yards). The rifled barrel gives the round a right-hand spin, ensuring accuracy and the fuze’s arming downrange. 

Although intended as a shoulder-fired weapon for direct fire, the M79 was also effective for indirect fire. The grenadier would place the butt on the ground, elevate the rear sight to the appropriate range and fire when the blade-sight and rear-sight pictures were properly aligned.

Often called the platoon commander’s or squad leader’s artillery piece, the M79 provided vital fire support to units throughout the war. Beginning in 1971, it was replaced in front-line units by the M203, which attached a grenade launcher to an M16 rifle; however, the simpler, more specialized M79 remains in service with militaries around the world and was used by some U.S. units in Iraq.    

First published in Vietnam Magazine’s June 2017 issue.