We talked earlier about the development of hand grenades and how they were, well, handy for a grunt to have. The problem with most grenades, though, was range. The range was limited by the arm of the thrower, usually resulting in a range of 30-35 meters. Various types of rifle grenades could be used for longer ranges, but they usually had poor accuracy and were awkward to use, sometimes requiring a soldier to unload his rifle, attach a launcher to the muzzle, reload with special ammunition, affix the rifle grenade, aim, fire the grenade, and go through the whole process again when he watched his grenade miss the target badly. When bad guys are shooting at you, this is a less than optimal workflow. Something better was needed.
In the years after the Korean War (1950-1953) the Army tried to develop a weapon smaller and lighter than a mortar to replace rifle grenades. Many attempts to develop a multi-shot weapon were failures. In the course of the development, though, a nifty 40mm round was developed.
The illustration above is actually a much later round (it is HEDP, or High Explosive Dual Purpose- it’s a HEAT round that also produces blast and fragmentation to kill or disable personnel). These rounds are much lower velocity rounds than the 40mm rounds used by the Mk-19. The low velocity 40mm rounds use a hi/low system. The propelling charge is in a small space and when ignited, produces a high pressure. This pressure bursts vents in a larger space behind the projectile. Venting into this larger space reduces the pressure and reduces recoil. Mind you, it also reduces the range of the grenade.
It didn’t take long for the Army to develop a weapon to use this handy round. In 1960, the M79 grenade launcher entered service. It was a pretty simple weapon, resembling a break-action shotgun on steroids.
The M-79 was popular during the Vietnam War, lobbing explosive grenades at ranges from 30 meters to 400 meters. For a weapon that lobbed its rounds at the target, it was surprisingly accurate. Wiki tells us a gunner could drop a round in a garbage can at 150 meters. In militarily useful terms, that means you could put a round through a window over a football field away. So the rifle platoon had a handy piece of artillery. Generally, each rifle squad had one troop who was armed with the M79, for a total of three in the platoon. The problem was that having three grenadiers meant three fewer riflemen in the platoon. It wasn’t long before some bright folks came up with the idea of mounting a grenade launcher under the barrel of an M16. Two versions were developed, the XM148 and the M203. The M203 was chosen in 1969 and soon replaced the M79 in most units.
Instead of one per squad, now both fire teams in a squad had a grenade launcher, for a total of six in the platoon. Better yet, no rifle firepower was lost. The M203 was slightly less accurate than the M79, but still good enough. The M203 is still in use today throughout the Army and the Marines, seeing service in Iraq and Afghanistan. In fact, it was only recently that the changing face of warfare, with an increased emphasis on low-intensity conflict, brought to light one of the M203’s shortcomings. Since the M203 is loaded by sliding the barrel forward from the breech, it can only load cartridges of a limited length. There are several cartridges available, including HE, HEDP, smoke and illumination rounds. But there are a range of less-than-lethal crowd control rounds in 40mm that the M203 just can’t fire because the rounds are too long to load.
The Army’s answer is the M320 grenade launcher. Fundamentally still just a simple tube, it’s barrel cants out to one side for easier loading, and since it is canted to one side, it can load and fire longer rounds.
The Army hasn’t given up on the dream of a multi-shot grenade launcher, but in 50 years, hasn’t come up with a practical weapon. The 40mm low velocity grenade looks to remain in service for quite some time.