For close range fighting the Army came up with two types of M79 rounds. The first was a flechette round which housed
approx 45 small darts in a plastic casing, these rounds were issued on an experimental basis. Later this round was replaced by the M-576 buckshot round. This round contained twenty-seven 00 buckshot which on firing was carried down the barrel in a 40mm plastic sabot, which slowed down in flight so the pellets could travel. 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. 