Gun Review: M79 Grenade Launcher

M79 MGL, c Nick Leghorn

There are guns, and then there are grenade launchers. Technically the same concepts apply, but one is exponentially more awesome than the other. So when Kevin pulled a pair of M79 grenade launchers and a case of practice grenades from his stockpile and declared that we were going to have a grenade lobbing contest, I knew the day was going to be epic. . .

In the beginning, there was the rifle grenade. The idea was simple: take a grenade, strap it to the end of a rifle, and then fire a blank. The force of the gasses from the blank round would send the grenade flying, much further than any soldier could lob it. It was the poor man’s mortar, but it had issues. It took time to swap from a live round to a blank, still more time to place the grenade on the gun, and even then it was notoriously inaccurate. And God forbid you forgot to change from a live round to a blank cartridge, your day would get pretty shitty in a hurry. The armed forces used this process straight through World War II, but once the conflict was over they realized the need for something better. Something that could lob a heavier explosive over a greater distance quicker, and without all that nasty recoil.

M79, c Nick Leghorn

The M79 and the 40mm grenade system was the result of those Army projects. The gun was designed to be a single-shot break-open style firearm that accepted the new 40mm grenade ammo, which looks and operates much like a standard shotgun shell — but with a little more firepower. You can definitely see the influences of single-shot hunting firearms in the design of the gun. The firearm was designed between 1953 and 1960, a time of transition between the more refined wood-and-metal designs of the pre-WWII firearms to a post-WWII focus on fast production and simple designs. So while it has some of the qualities of an old-world gun (the wood stock, for example) the internal parts and the metal fittings definitely feel like stamped and mass-produced parts.

While the gun and the processes to make it had been in use since the days of yore, the real difference in this gun was the ammunition.

M79, c Nick Leghorn

The 40mm grenade uses a unique “high/low” pressure system to fire the rounds. A firing pin strikes a primer at the back of the grenade as usual, but instead of setting off a packed powder charge like in normal ammunition, the primer sets off a small package of powder that sits in an otherwise fairly empty case. The reason for the low pressure lifting charge is that the Army wanted soldiers to be able to fire the grenade comfortably, while still getting a good 75 meters per second out of the projectile. Thanks to the system, a plastic cup can be used for the practice rounds instead of a standard brass or metal cartridge (the live rounds use metal for reliability reasons).

That low pressure and low velocity round is what gave this gun its nickname, the “blooper.” The reason is that instead of a sharp crack as the round goes off, the gun makes a distincitve “bloop” sound as the low velocity gasses escape from the barrel. Due to those low velocity rounds, the gun needs to be canted at a much more exaggerated angle in order for the rounds to hit their target. As a result, the stock was tilted (compared to the bore) and a set of the most laughably large ladder sights I’ve ever seen were installed.

M79, c Nick Leghorn

The sights can either be raised or folded down by pressing a plunger on the right side of the mechanism. When folded, a simple notch in the rear of the sight assembly acts as the rear sight and gives the shooter a reference point for aiming. When raised, the sights work like any other ladder sights, just more massive. Not only is there more vertical travel, but the sights are wider with more room in the middle due to their forward position. Where normally the sights are right on the shooter’s nose, these are set about halfway down the barrel (thus the need for more room to see what you’re doing). The sights are clamped onto the barrel, and so can be replaced if necessary.

M79, c Nick Leghorn

The barrel, as you would expect, is massive (please excuse the dirt and grass, this GL hasn’t been cleaned in a while and didn’t function). But where you’d expect 1960’s era technology to have a straight smooth wall in the barrel, there is indeed some rifling cut into the sides. The grenade uses a brass ring around its circumference to grip this rifling and spin it, giving the grenade launcher an amazing level of accuracy.

Speaking of that level of accuracy, we had a little contest to see which among us on the range that day was the best shot. Johnny (the tattooed gentleman I’ve used as my model for some of these reviews) used to be a weapons instructor for some military units that don’t officially exist. And from 50 yards away, he did the following to a B/C zone steel plate:

Grenade impact, c Nick Leghorn

That, my friends, is a PERFECT center-mass impact. With a grenade launcher. From 50 yards away. I wouldn’t have believed it if I hadn’t seen it with my own eyes. And the reason that I wouldn’t believe it is that the gun is (comparatively) so terrible to fire. The trigger is extremely heavy and none too well machined. The stock doesn’t feel comfortable at all. And the impulse from the recoil, while better than a rifle grenade, is still extremely stout. The military has since implemented a “low velocity” version of the 40mm as well as a higher velocity version for the Mk. IXX grenade launcher, but even using the same practice rounds the recoil was so much more pleasant from either H&K’s M320 or FN’s grenade launcher.

M79, c Nick Leghorn

In almost every other way, the gun operates much like a cheap break-action firearm. There’s a lever in the back to break open the gun, and there’s an extractor that shoves the spent case out of the chamber for you. It doesn’t fly out, though, so you still need to pick the spent case out of the gun before reloading.

The best part about the M79 is that you, as a private citizen, can not only buy one for a reasonable price but you can build your own. The M79 is technically a “destructive device,” a category of firearm that is regulated by the ATF but the registration is still open (unlike machine guns). You can make one at home from a kit and legally register it, then use it to your heart’s content. Or, if you aren’t mechanically inclined, I’ve seen them for sale for about $5,000. The real trick is keeping the thing fed, since the equation swaps from being “rounds per dollar” to “dollars per round.”

The M79 is a fun gun, extremely accurate, and a definite conversation starter. And it just looks friggin’ awesome in a 1980’s action movie kind of way. Needless to say, I want one.

M79 Grenade Launcher

Caliber: 40mm
Barrel: 14 inches
Size: 29 inches
Weight: 5.95 lbs empty
Capacity: 1 round
MSRP: $5,000

Ratings (Out of Five Stars):
All ratings are relative compared to the other weapons in the gun’s category.

Accuracy: * * * * *
For a grenade launcher, this thing is dead on. You couldn’t ask for more.

Ergonomics: * * *
The stock is canted to make firing more natural, but it just doesn’t suit me very well. Also, reloading the thing is a pain in the butt.

Ergonomics Firing: * * * *
Stout recoil, but otherwise perfect.

Customization: N/A
Uh…no. Absolutely not.

Overall Rating: * * * * *
Fun, cheap, and readily available. Sounds like my ideal girlfriend, actually.