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

Specifications
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.

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About Nick Leghorn

Nick Leghorn is a gun nerd living and working in San Antonio, Texas. In his free time, he's a competition shooter (USPSA, 3-gun and NRA High Power), aspiring pilot, and enjoys mixing statistics and science with firearms. Now on sale: Getting Started with Firearms by yours truly!

60 Responses to Gun Review: M79 Grenade Launcher

  1. avatarDave says:

    What involvement does the ATF have with procuring one of these beasts?

    • avatarHasdrubal says:

      A “destructive device” includes any weapon intended to fire a projectile over .50″ with the exception of shotguns. As the grenade launcher is not primarily a shotgun, it falls into this category. Black powder guns do not, though.

      Each explosive grenade counts as a separate destructive device, but I believe inert rounds (like chalk filled rounds that still fire, but do not explode) do not.

      • avatarTCBA_Joe says:

        A bit of a correction. Because the BORE diameter is >.5″ it is a destructive device. While there was an attempt to classify ammunition with a diameter >.5″ as explosives, the ATF dropped this attempt. The .50 BMG has a diameter of .510″ and is not a DD because the rifle bore itself is .50″ on the lands.

        As for the rounds being DDs, that only applies if the round is an explosive itself. Other rounds (chalk, beanbag, shot shell, gas, smoke, beehive) are not DDs in and of themselves.

  2. avatarTom in Oregon says:

    “I knew the day was going to be epic. . ”

    Holy crap. I’m jealous. Again. Still.

  3. avatarAnonymous says:

    Homemade guns you don’t have to register them or serialized them unless you sell it/transfer it in my state (think 80% lower). Is this the same with the M79? Or similar?

  4. avatarMichael B. says:

    It can be turned into a 40mm shotgun.

    About 1966, this was replaced by the M576 buckshot round. Containing twenty 24g metal pellets[12] (M576E1) or twenty-seven 24g metal pellets (M576E2), this round could be devastating at close ranges. However, as range increased, the shot spread out so rapidly as to be ineffective. The M576E2, despite the greater number of shot, was less effective at range than the M576E1, because its shot spread out much more quickly and could completely miss the target.

    http://en.wikipedia.org/wiki/M79_grenade_launcher

    DO WANT.

  5. avatarDavid says:

    Nick,

    Can I distill down your Karmatic essence? Seriously, one drop is probably good enough for me to win the lottery – or at least find a Franklin on the road. Please tell me you have some painful bone disorder cuz your job makes us all more than jealous.

  6. avatarDJ9 says:

    All the 40mm grenade launchers I fired in the service were very accurate, if the shooter did his part. I can remember multiple hits on a 55 gallon drum at distances of 2 to 3 football fields away, with grenades that had a 50% kill probability in a 10m circle (IIRC; it has been a while…).

    The only thing I hated about the M79 was the safety button functioning and position. Once you fired and broke the weapon open to reload, the safety went back to the “On Safe” position automatically. If the shooter didn’t remember to push it back to “Off Safe” prior to trying to fire, often it would reveal a massive jerking of the trigger and anticipatory lunge forward into the weapon when it didn’t fire, knowing it was about to smack you in recoil. Highly entertaining for onlookers, but rather embarrassing for the shooter(s). The safety was placed on top of the tang, which provided quick access, but also put its razor-sharp corners near the web/thumb of the shooter’s hand (see the second photo, above, for an excellent example; he’s clear, but not by much). Grabbing and firing the weapon quickly could (and often did) result in the shooter becoming an open-air temporary blood donor and pulling a little wad of flesh off the safety as they passed it to the next shooter.

    Good times, good times…

    • avatarKCK says:

      Safety, no different from Savage double 20Ga,
      Resets on break, not a bad idea really.
      Trained myself to click off as I would swing to fire.
      Hate to launch an m79 in the Fox hole.

      • avatarDJ9 says:

        Yeah, I understand the concept and agree with it in theory, but it was the only weapon in the inventory that I ever came into contact with that put itself back “on safe.” Everything else, you manually moved the safety to “off”, and you manually moved the safety back to “on.”

      • avatarSteve Evans says:

        Frankly the only time I DIDN’T get a kick out of my M203 (basically the same thing mounted under an M16) was in an emplaced position. Then I’d usually rig up something to eat the recoil instead of me. Usually a little stand in the bottom of my emplacement where I’d already calibrated a stick with the sights, so I could use it like a small mortar and let the buttplate smack into the sod. I got VERY good at this though fortunately never had to use it for real as it was my “holy shit I’m pinned and I can’t do crap” technique.

        Also my “in the breech” carry round was the shotgun round, for many of the reasons listed above it’s the best round to have ready if you get caught in an ambush at close range. It may not hit shit beyond 10 meters, but it’ll make anyone within 50 hide behind something solid.

    • avatarDyspeptic Gunsmith says:

      I had a friend who was a VN USN vet – in the SeaBees. He said the “bloop tube” (as he called it) was his favorite weapon, and that with practice he could put a round through the windshield of a truck 250+ yards away most of the time.

      As it turned out, he said, he had several very good opportunities to do exactly that.

      He said that putting WP rounds into NVA trucks’ cabs was highly entertaining – and effective.

      • avatarIdahoPete says:

        REALLY fun to shoot – easy to drop a practice round into a 55 gal drum at 150-200 yards, within the first 10 shots at basic training. I knew Vietnam vets in 1972 at Ft. Hood (1st Cav) who could put one through a bunker slit at 400 yards. Kind of like having your own personal 81mm mortar, except a whole light easier to carry.

  7. avatarBDub says:

    “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.”

    Its the other way around. To delivery a round on top of an entrenched enemy position, you need high angle of trajectory. To do this you need a low velocity round. A flat trajectory would severely limit its usefulness.

    This is in direct contrast of newer grenade launcher rounds that are being developed for urban conflicts. These systems have flatter trajectories and electronic detonators that are keyed off of a laser ranging system. This allows you to range off of a wall and then shoot a grenade right over the top of it (or through a window) and have the grande detonate just after passing the wall. Without the advent of the electronic detonator and laser range finder you need a system like the M79 to lob over the wall.

  8. avatarPaul W says:

    Wait, kits? Where/how? I always wanted a mortar and this is close enough.

  9. avatarBDub says:

    “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.”

    Its less about accuracy and more about the grenade fuse mechanism. The fuse on a 40mm grenade is activated by the spin on the round, assuring that the grenade is safely down range before its “live”. It think its like 40 meters or so (outside the effective range of the blast). The paint round you guys are using don’t do this, nor do the AP rounds (which are just gloriously large shotgun shells).

    • avatarDJ9 says:

      Back when I was a user/trainer, the rounds armed within 14meters to 27m of the muzzle, but I see they have rounds that arm MUCH closer nowadays (including a High Explosive round that arms at 8-10 FEET?!?):

      http://www.inetres.com/gp/military/infantry/grenade/40mm_ammo.html

      Good news: no danger of ricochet/bounce-back (a problem in forested areas or urban terrain).
      Bad News: you are inside the kill radius if it hits something very close.

    • avatarjwm says:

      It’s been many years, but you’re right about the safety setting on the fuse. I recall 25 meters, but as I noted too many years gone by to be sure. In thick cover a simple contact fuse could just as easily kill the operator as the target.

      If I recall correctly the old RPGs had a 2 way fuse on them. Contact and timed. If the round didn’t impact within it’s time limit it would detonate. A practised individual could air burst those RPGs with a real bad effect on the recepient. For some reason I seem to recall we called those RPGs B40s. Maybe the passing of time has me confused.

      • avatarDJ9 says:

        I’m pretty sure you are right, as I was once tasked to advise on force protection, and one of the things we looked for was cover within 900m, as that was max range before self-detonation for the then-common RPG7.

        • avatarpat says:

          What do you mean “then common”?

        • avatarDJ9 says:

          pat, I was referring more to the grenade/projectile commonly used at the time, as I don’t know what the specs are for later grenades used by this system. The system itself has been ubiquitous in Eastern-bloc and 3rd-world countries for a very long while, but like every other weapon system, parts of it do get upgraded over time. The Wiki page for the RPG7 shows several different kinds of grenades, some of which were introduced after I left service, I believe, so I am unfamiliar with their specs and fuzing.

  10. avatarA-Rod says:

    Tomorrow on TTAG…Nick will compare and contrast the M26 Modular Accessory Shotgun System and the Masterkey by Knight’s Armament Company for the M16/M4 platform. Stay tuned folks.

  11. avatarBLAMMO says:

    (grrr … jealous, … bitter, … angry, … hateful, … resentful, … grrrr …)

  12. avatarRockOnHellChild says:

    If any anti gun folks are reading this, there’s a good chance they’re foaming at the mouth…

    • avatarAkira says:

      Well they support our right to own guns for hunting, but clearly something must be done about all this grenade launcher crime.

      Oh wait…

      • avatarTTACer says:

        What we need is commonsense 50+ year old grenade launcher control. For the children.

        • avatarPhilthegardner says:

          Or common sense WW2 era M1 Garand and M1 Carbine control… oh sorry. That’s already been done. You can’t pull one over Barry. He’s a sharp ‘un

  13. avatarHasdrubal says:

    I wish they had kept these and never gone to the M203. They never let us use the things, so all it did was make your rifle heavy. And since we knew we would never use them, we had barely enough range time to remember the controls (yes, they are simple controls, so it only took about one range every two years).

    I’m becoming a big fan of bullet trap or pass through grenades. Give each man in an infantry platoon two of these, and your react to ambush could be devastating.

    • avatarjwm says:

      Yeah, we had the old m16. The 2 things that were good about it was the FA giggle switch and it’s light weight. I had no contact with the 203s, and am glad for it. I never understood the need to try to make an m16/AR heavier and more complicated than it already was. Some reasons for weight gain were improvements. A heavier barrel and sturdier forearm.

      But if you’re beating the weeds or patrolling the urban areas your primary concern should be reliability. Switches, buttons, wires, batteries and all the hoopla that go with them would do nothing but increase weight and decrease reliability.

      If I was somehow forced to carry an M4 or other varient on the Stoner system all I would put on it extra would be an opticical sight.

      • avatarSteve Evans says:

        Easier to stop an incoming VBIED with a 40mm HEDP round than with those itty bitty bullets. Both active duty and in the guard I requested the M203, even when I was a tank crewman, for the extra firepower and the versatility that some of the specialty grenades gave me. Want someone out of a building for sure? Fire a magnesium parachute flare through the window. He’ll leave.

  14. avatarRuss Bixby says:

    Y’know, I’ve a history of making and playing with interesting weapons.

    Mayhap I’ll take a hand at making something akin to one o’ these…

  15. avatarPK says:

    You folks do realize that you can buy a 40mm for under $2k, right? I have a standalone 40mm that was under $800. With tax it didn’t quite break $1k. Still one of the most delightful firearms I own.

  16. avatarAdam says:

    Somebody please correct me if I’m wrong, but doesn’t the ATF regard each grenade round (even training ones) as a destructive device and thereby subject to a tax stamp.

    If so, that is one expensive round.

  17. It’s what every home needs for self-defense….

    : )

  18. Go get the Roach, man!

  19. avatarBruce L. says:

    One of my favorite weapons, but I was usually happier if someone else was using and lugging it and the ammo. It also tended to draw fire, for some strange reason.

    • avatarSteve Evans says:

      The lugging the ammo part stunk, fortunately they rarely broke the cases open when I was in, as then they’d have to account for it and return the partial cases, so they mostly sat in the platoon commanders track unless he decided to get adventurous that day and let us get some practice in.

  20. avatarfreakshowSMVM says:

    Even better than the m79 is to buy a 37mm picatinny m203 clone, sold as a flare gun. Does NOT need to be registered as a DD If you only use flares and chalk rounds.you can then later register it and once approved, use lethal rounds. This is under half the price of the m79 and does not have the mandatory several month nfa wait. Even legal in NY and CA as a flare gun

  21. avatarshawn says:

    How the frack is $5K cheap?

    • avatarChainsawWieldingManiac says:

      You can buy a Spike’s Tactical 37mm launcher with stock for $600, get a DD stamp, and machine the bore out to 40mm. That’s about a thousand bucks or so. I’d do it for the lolz, except I have no place to shoot one.

    • avatarTTACer says:

      $5k is pretty cheap for anything that involves the BATFE&RBFs

  22. avatarBRY says:

    At Camp Pendelton in 1976, we were taught to place the butt stock under our arm (tucked up in armpit) rather than to our shoulder. Our targets were about 250 yards away.

  23. avatarEspantoon says:

    I carried one of these during my first tour in Vietnam in 1967. IIRC, basic load was 50 rounds of 40mm HE, a few buckshot rounds, and a .45 sidearm. In those days I was a scrawny 18 year old, and after intense firefights my shoulder would be black and blue from the recoil and so sore I could barely raise my arm. Loved that weapon, and the .45 which I also fired in anger.

  24. avatarAccur81 says:

    All of my experience was with an M203. They were relatively accurate also, but range estimation was critical. That thing definitely had a rainbow trajectory. Bigger up the range and you definitely had a miss.

  25. avatarDave Lewis says:

    My brother carried an M-79 as a grunt in the 1st ID. He’ll agree with the comments about the weapon’s accuracy. He could hit out to about 300 meters but needed a spotter because he was shooting beyond the sights and needed somebody to watch where the rounds were falling. At the other limit he popped a guy at very close range with an HE round and the round hadn’t flown far enough to arm. Pat knocked the very skinny NVA soldier down with the impact of the round and finished him off with a .45. Spare rounds were carried in Claymore mine bags. He also stated that the buckshot rounds were pretty much useless. The shot pattern opened up so fast that you were probably not going to do any harm to the bad guy.

    Lots of “experts” have claimed that few if any enemy soldiers were ever killed with a .45 automatic. Ask old 79 gunners if that’s true – from what I understand they tended to be very good pistol shots and used their side arms quite often in close combat.

    • avatarjwm says:

      The m79 was a stand alone weapon. In close you’d better have something else, like the .45. That was one of the selling points of the 203. It gave the grenadier a rifle in close work.

  26. avatarJoseph says:

    After his 2 tours in Vietnam, my dad distanced himself from guns to the point i was learning to drive before i got my first BB gun. But back in ’83 or so, I got to go to a weekend drill with him (he was a mess sargeant in a guard unit here.) I watched my dad teach 20 somethings how to rig/disable claymores, he broke M-16s down to the trigger mechanism…and then i got to watch him take a M-79 to the range. i think i was too young to understand what porn was, but the way he treated that weapon was something pretty close to it.
    He never used the ladder sight, and was placing shots where people wanted them.
    as i said, he wasn’t found of guns, but on the way home, he was smiling, and i remember him saying, “You should see what a beehive does to a treeline.”
    I can’t swing the $$$ for a real M-79, but i am definitely getting one of the Airsoft versions. 1:1 scale and weight, similar features and well, i intend to display it more than fire it, so it’s more of a reminder of a great day with my dad.
    if you can go to a gun show, club or somewhere and get the chance to just watch a pro use the M-79, do it. it’ll put a tear in your eye and give you an incurable case of awesomeness.

  27. avatara.a. says:

    As somebody who has used the M-79 in Afghanistan, I can say it is probably the most point and shoot grenade launcher ever made. A good shot is able to reliably hit center mass on a man size target at 100 yards and a great shot should be able to at 150 with his first shot. The ladder sites are pretty much useless once you have put more than 10 rounds through the thing, it is just that easy to shoot.

  28. avatar2hotel9 says:

    Trained with 79s and 203s and have to say I preferred the 203. I really like having both weapons when la merde strikes la ventilator. Having single shot dedicated weapon in a high volume fire situation is NOT my idea of optimum effectiveness. That said the 79 was much more accurate even with minimal training time.

  29. avatarzsolt sass says:

    Every freedomfighter must have the m79 to defend his freedom and to use it to liberate the usa from hussain obamas gestapo and dictatorship.Comrads in arms buy one or built one and use it to liberate your country. I love the m79 a real freedomfigter tool.Get some c4 too for the big bang.Deal the fist deadly BLOW.comrade,freedomfighter,zsolt sass

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