"BLOOPER" THE M-79 GRENADE LAUNCHER:
This weapon first appeared during the Vietnam war and closely resembled a large bore, single barrel, sawn-off shotgun. The first M79 Grenade launchers were delivered to the US Army in 1961.
The M79 was designed as a close support weapon for the infantry, and was intended to bridge the gap between the maximum throwing distance of a hand grenade, and the lowest range of supporting mortar fire. An area of between 50 and 300 meters.
The M79 was a single shot, shoulder fired, break-barrel loading weapon which fired a spherical 40mm diameter grenade. The M-406 40mm HE grenades fired from the M79 traveled at a muzzle velocity of 75 meters per second, and contained enough explosive within a steel casing that upon impact with the target would produce over 300 fragments at 1,524 meters per second within a lethal radius of up to 5 meters (?). Stabilised in flight by the spin imparted on it by the rifled barrel the grenade rotated at 3,700rpm, this in turn after 15 meters(?) of flight armed the grenade.
Field Manual of the 40 MM Grenade Launchers, FM 23-31