The M79 40mm Grenade Launcher was the primary grenade launcher of the US during Vietnam. The weapon was introduced just prior to the outbreak of the war, only to be replaced before the war was over, by the M203 40mm grenade launcher. The weapon was a single shot, break-open, breach-loading system with a wood stock.

M79 40mm Army Ranger Weapon

Primary Function Grenade Launcher
Manufacturer United States
Bore Diameter 40mm
Weapon Length 29 in
Weapon Weight 6.6 lbs
Max Effective range    1,312 ft
Muzzle velocity 246 fps
Rate of fire Breech Load
Ammo capacity 1 rnd


M79 Army Ranger Weapon
P/75 Ranger Terry Roderick on patrol near the Ben Hai River, Demilitarized Zone, South Vietnam, 1970.

During the Vietnam War, each LRP/Ranger team going out on patrol usually brought the M79 as secondary weapon and was used to fulfill several roles. It was effective for the point man to use with a buckshot round, the limitation being that if contact was made, only was shot could be made before having to reload.

The M79 was also used with smoke grenades to mark targets for close air support and with teargas to break contact with the enemy. When using High-explosive rounds, the vegetation limited it's effectiveness due to the short range engagements that were typical during the Vietnam War. For short range situations, hand grenades were usually preferred as they could be used without carrying an extra weapon and their fragmentation effect was more effective than a 40mm round.