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.

40mm_m433The 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.

m79_afmilThe 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.

M203 mounted on an M4 carbine
M203 mounted on an M4 carbine

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.

xm320-m4The 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.

8 thoughts on “Thumper”

  1. When you say multishot do you mean like a cartridge system or something that sprays out a pattern of them at once or maybe something else?

    Nice info btw. So many weapon letters and numbers.

  2. Speaking of multi-shot grenade launchers, I seem to recall the Germans in WW II had a “wonder weapon” (’cause only the Germans can design good stuff right?) which was basically a cross between machine gun and mortar. Fired 50mm “grenades” or mortar bombs to a range about 300m. Wonderful idea, but just had one problem…. Darn thing weighed a couple thousand pounds (the gunner sat in it). It was used in some fixed fortifications, but found also to jam a bit.

    For all practical purposes, the Army may be “dreaming” of a multi-shot grenade launcher, I dare say for the grunts, it would be a nightmare!

  3. Well, for the most part, multi-shot means more than one projectile fired prior to needing to reload. Several ideas have been tried, from a drum-fed 40mm grenade launcher, to a clip system. The drum has the advantage of being a simpler system (picture an extremely large revolver), but it is very heavy. The clip fed system (imagine a very large semi-auto pistol) was completely impractical. The clip itself would measure over 2.5″ X 5″ X 10″ or more.

    What you guys are talking about above is a fully automatic grenade launcher, which IS currently in US service. The Mark-19 is a belt fed, fully automatic grenade “machine gun”. I don’t recall the cyclic rate on it, but basically, you could clear a ridgeline in a matter of seconds (or at least convince the bad guys that advancing was a poor plan).

  4. Too big and too heavy is probably the problem. I guess they’d need smaller lighter grenades that can do the same job.

    The Mark 19 does sound nice. Well nice for the owner, not so nice for the others.

  5. When we speak of “multi-shot grenade launchers” we are looking at two different animals. The first was a man portable system that could fire multiple shots before reloading. Think of the M203 or M79 being a pump gun instead of a single shot. The problem is that to have an effective grenade, you need some thing fairly large like a 40mm, but then you end up with an unwieldly weapon. That’s the same problem that applies to the revolver type weapons, they are just too big.

    But the Army did pursue an automatic grenade launcher as a heavy machine gun, the Mk19- if you guys clicked the links, you’d know that. The Mk19 also fires a 40mm grenade, but it is a vastly different grenade, firing at high pressures and much higher velocities. Instead of a max range of 400 meters, it has a max range of 2000 meters. Now, there was also an “automatic” grenade launcher, Mk20 that fired the same grenades as the M79/M203. It was belt fed, but fired by rotating a crank, much like an old gatling gun.

  6. I also seem to recall at one point the Army was talking about using a 20mm grenade launcher that would work like a pump-action shotgun. Can’t say I’m too hopeful about the utility of the charge a 20mm grenade could pack, but they were talking about proximity fuses and all kinds of hi-tech gadgets that these grenades and their launchers would carry. Part of the Full Spectrum Warrior program as I recall.

    Here we go:

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