The late 1950s started as an era of US Military Advisors in Saigon but as we all know developed into a major US Troop escalation by 1961 when ‘boots on the ground’ tripled, and then tripled again a year later. The number of US Personnel ultimately went to 500,000 in 1967 and the M79 found a ready home in the thickest fighting.
In 1961 the M79 was put into service and they got it right. The rifled grenade launcher, manufactured initially by The Springfield Armory, was ideal for Vietnam. The Bloop Gun was suited to most terrains and could multi task successfully because of the effective array of munitions. The sole drawback, it was single shot.
Called a Bloop Gun, Bloop Tube or Thumper Gun by the troops due to its unique High-Low Propulsion System, subsequently unique “mid range” of effectiveness and cartoonish sound the gun made when fired, in the hands of an experienced grenadier the M79 could arc a HE Fragmentation round into the other guys lap, taking out everything within a 5m (5.47 yards) radius.
To get a better picture of one these rounds impact damage, mentally picture a dome over a 30-foot boat. After a round hits that target, nothing will remain alive inside the dome though the boat will remain relatively intact. Up, down and out the HE FRAG (high explosive) rounds were omnidirectional with no survivors. The interlinked bunker networks of the Viet Cong were the most obstinate targets in the hillsides. High Explosive FRAG in concert with an incendiary round was the requisite combination. Vietnam was not a cotillion.
In consequence, the M79 40mm, the ‘ugly little shotgun’, filled an essential gap in the Marines skirmish abilities and troops loved to have a Bloop Gun with them because of its flexibility. M79s owned the crucial middle distance beyond hand grenade range and up to 400m (438 yards) where the mortars could join the festivities. Bloop guns were dependably lethal from 50-100m (55-109 yds.) just beyond hand grenade range, and able to blanket an area up to 375m (410 yards) with antipersonnel rounds. And it was really in the variety of rounds they fired that the Bloop gun shined; Units could switch battle tactics with the two second swap of a canister.
By preference M79 rounds could be OO buck, a .22 long rifle array or that proven crowd pleaser Willy Peter, a.k.a. White Phosphorus. If scouts or aerial reconnaissance reported enemy troop concentrations, your four man Fire-Team joined up with three similar Fire-Teams to form a Squad, usually bringing in a Bloop gun and sometimes a machine gun crew if enemy numbers warranted the extra attention.
The M79 could back up most situations as well as provide instant illumination or complete smoke cover with a pull of the trigger. If you were on patrol with both weapons along, you should see action.
Discharged into a tunnel complex, a smoke grenade will filter upward to show concealed openings revealing escape routes. In the bush hand grenades were favoured over rifles and came in two flavours, baseballs for distance and pineapples to lob at enemy probing your immediate perimeter. The best distance with a good arm is 50m (55 yards) and you only needed to be in the vicinity. Crucially grenades presented no revealing muzzle flash which is a potential death sentence to rifleman.
If enemy troops were attacking over an open area the Fléchette round was a show stopper. Fléchette is a French word which translates into minuscule arrows (fléche) similar to dart tips with a tail designed for stable flight. They travel at supersonic speed in every direction and wreak havoc with piercing efficiency.
Marines were called ‘hill hoppers’ as the prevailing strategy was to control the mountain tops and passes and fire downward on the Ho Chi Min Trail. Soldiers were deposited from peak to peak by helicopter as objectives were achieved or lost. At night you held the hill top encampment heavily encircled with claymore mines attached to trip wires and rationalizing that even the C Rations, back at base, dated 1943 would be good now.
Various types of strikes could be called in as required including artillery, mortars, aircraft for troop concentrations and for anything dire (but what the hell wasn’t). In some stubborn situations and given the units and targets proximity, Naval Artillery can deliver a one ton shell from miles away. There won’t be much left of course.
Therefore a favourite tactic in block to block situations was to determine the location of enemy fire and if protected by an exterior wall, put some HE on the other side of it, usually off the other wall across the “complex”. Good outcome for you in terms of enemy casualties and limited damage to the structure.
The Bloop gun rifling spins the projectile to arm itself using centrifugal force. This occurs past 30m (33 yards) igniting an internal fuse and then explosion on contact providing a safe distance, for the gunner.
The M79 was replaced in 1971 by the M203 under barrel grenade launcher designed for the US M16 and the M4 Carbine but still remained a single shot add on that used the same ammo as the M79.
The M79, although supplanted by the M203, has been in service in the armed forces of Australia, Turkey, Israel and some South American nations with versions now produced by Daewoo in South Korea as well as by Milcor in South Africa. They claim that there is still a demand.