M79 with the leaf-type sight unfolded.
Type Grenade launcher
Place of origin United States
In service 1961-present
Used by See user
Wars Vietnam War, Cambodian Civil War, Falklands War, Iraq War
Designer Springfield Armory
Manufacturer Springfield Armory, Action Manufacturing Company, Exotic Metal Products, Kanarr Corporation, and Thompson-Ramo-Woolridge
Number built 350,000 (U.S. only)
Weight 2.93 kg (6.45 lb) loaded
2.7 kg (5.95 lb) empty
Length 73.1 cm (28.78 in)
Barrel length 35.7 cm (14 in)
Cartridge 40x46mm grenade
Rate of fire 6 rounds/min
Muzzle velocity 76 m/s (247 ft/s)
Effective range 350 m (383 yd)
Maximum range 400 m (437 yd)
Feed system breech-loaded
Sights Blade and leaf type
The M79 grenade launcher is a single-shot, shoulder-fired, Break-action grenade launcher which fires a 40x46mm grenade and first appeared during the Vietnam War. Because of its distinctive report, it earned the nicknames of "Thumper", "Thump-Gun", "Bloop Tube" and "Blooper" among American soldiers; Australian units referred to it as the "Wombat Gun". The M79 can fire a wide variety of 40 mm rounds, including explosive, anti-personnel, smoke, buckshot, flechette, and illumination. While largely replaced by the M203, the M79 has remained in service in many units worldwide in niche roles.
The M79 was a result of Project Niblick, an attempt to increase firepower for the infantryman by having an explosive projectile more accurate with further range than rifle grenades, but more portable than a mortar. Project Niblick created the 40 x 46 mm grenade, but was unable to create a satisfactory launcher for it that could fire more than a single shot. One of the launchers at Springfield Armory was the single-shot break-open, shoulder-fired S-3. It was refined into the S-5, which resembled an over-sized shotgun. Unable to develop a suitable multi-shot launcher, the Army adopted the S-5 as the XM79. With a new sight, the XM79 was officially adopted as the M79 on December 15, 1960.
In 1961, the first M79 grenade launchers were delivered to the US Army. Owing to its ease of use, reliability, and firepower, the M79 became popular among American soldiers, who dubbed it "the platoon leader's artillery". Some soldiers would cut down the stock and barrel to make the M79 even more portable.
However, its single-shot nature was a strong drawback; having to reload after every shot meant a slow rate of fire and therefore an inability to keep up a constant volume of fire during a firefight. Also, for close-in situations, the minimum arming range (the round must travel 30 meters to arm itself) and the blast radius meant a grenadier would have to either resort to a backup pistol, if he had one to begin with, or fire and hope that the grenade would not arm itself and act as a giant slow bullet. Specialty grenades for close-in fighting were created to compensate, though a soldier did not always have the luxury of being able to load one in the heat of battle. Moreover, its size meant that a soldier with an M79 would be dedicated to being only a grenadier, and if he ran out of ammunition had nothing but a pistol and knife to contribute to a firefight. Underbarrel grenade launchers, such as the XM148 and the M203, where the grenade launcher attaches to the rifle, were developed during the Vietnam War, allowing the grenadier to function also as a rifleman.
The XM148 was plagued with problems and the project was dropped. The M203 was a success, and was standardized in 1969; it had replaced the M79 by the end of the war, though M79s were still used in Reserve and National Guard units.
Some US Navy SEALs and Army Special Forces in Iraq have been seen using the M79 in recent years. Most likely due to its greater accuracy and range compared to the M203 (350m effective versus 150 m effective on the M203). The M79 has seen notable limited use during Operation Iraqi Freedom, such as for clearing IEDs.
Visibly, the M79 grenade launcher resembles a large bore, break-action, sawed-off shotgun, and is simple in design, having only five parts: a receiver group, a fore-end assembly, a barrel group, a sight assembly, and a stock. The fore-end assembly beds the barrel to the receiver. The stock is made out of wood or fiberglass. A rubber pad affixed to the shoulder stock to absorb some recoil. The front sight is a fixed blade. The rear sight on the M79 is a folding ladder-style leaf-type sight. When folded, the leaf sight acts as a fixed sight for close range. A grenadier may simply point and shoot with high accuracy. When unfolded, the leaf-type sight could be adjusted for ranges from 75-meters to 375-meters, in 25-meters increments. Additionally, Appendix A of U.S. Army field manual for the M203 includes instructions for attaching the M16 rifle grenade sight to the M79's stock and marking the sling for indirect fire at elevations greater than 40°.
While not a Manufacturer, Milcor/Mechem of South Africa do re-manufacture M-79 grenade launchers to more modern standards. They replace the leaf sight with an optical one and replace the wooden stock with a modified R-4/R-5 stock.
M79 and FN MINIMI
M79 being set up for display
The M79 is easy to operate. To load, the grenadier pushes the barrel locking latch on the receiver group to the right. Gravity will pull down the barrel, breaking it open, and exposing the breech. The hammer is cocked when the breech is opened. A round then may be loaded. The break action must then be closed manually. Closing the breech will cause the barrel locking latch to return to center. To fire, the grenadier pushes the safety forward, reveal
See also United States 40 mm grenades
Many different ammunition types were produced for the M79 (and subsequently for the M203), outside of the smoke and illumination rounds three main types emerge: Explosive, Close-range, and Non Lethal Crowd Control. The break-open action of the M79 allows it to use longer rounds that the standard M203 cannot use.
The M406 40 mm HE (high explosive) grenades fired from the M79 travel at a muzzle velocity of 75 meters per second. The M406 contained enough explosive to produce over 300 fragments that travel at 1,524 meters per second within a lethal radius of 5 meters. This round incorporated a spin-activation safety feature which prevents the grenade from arming while still within range of the shooter; it armed itself after traveling a distance of about 30 meters. Even though the round would not arm at point blank ranges, the round still had enough kinetic energy to kill or seriously injure its target.
 Close range
A less-lethal round is loaded into an M79
For close range fighting two styles of M79 rounds were developed. The first was a flechette or Bee Hive round which fired 45 10-grain steel flechettes. Flechettes proved to be ineffective because they would often not hit point-first and penetrate. Instead they would hit sideways and bounce off. About 1966, this was replaced by the M576 buckshot round. Containing twenty pellets of #4 buckshot (M576E1) or twenty-seven pellets of #4 buckshot (M576E2), this round could be devastating at close ranges. However, as range increased, the shot spread out so rapidly as to be ineffective. The M576E2, despite the greater number of shot, was less effective at range than the M576E1, because its shot spread out much more quickly and could completely miss the target.
 Less-Lethal / Crowd Control
The M79 has been used extensively also for crowd control purposes where it is desirable to have a weapon dedicated solely to less-lethal force. The three common less-lethal rounds are the M651 CS gas, the M1006 sponge grenade, and the M1029 Crowd Dispersal rounds.