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IWA International’s Smoothbore Smile-Maker: Say Hello To My Little Grenade Launcher

There’s no denying the sex appeal of a grenade launcher. Whether you’re a war historian, video gamer, or movie buff, your likelihood of encountering some kind of pop-culture grenade launcher reference is pretty high. 

But the government doesn’t like the idea of a near-peer conflict on home soil. So real grenade launchers and ammunition — of the 40mm high-explosive variety — fall under the ATF category of “Destructive Devices” that adds layers (plural) of bureaucracy between you and the prospect of your owning a grenade launcher capable of lobbing HE ammunition.

While 40mm grenades are too destructive for the hands of mere mortals, 37mm grenades are just destructive enough to purchase direct without so much as a 4473 in the way. Some may remember the 37mm subculture of the 1990s, which brought about a small but kooky buffet of launchers and accessories. There were 37mm copies of the M203 for those looking to LARP or clone. 

Then, there were a series of odd duck accessories, like a “shell” that accepted half a dozen .22LR rounds that would go off simultaneously when the parent shell was hit by the firing pin — the poor man’s beehive round. There were also plastic chamber inserts that allowed the 37mm launcher to fire various gauges of shotgun shells. 

While most of this market died quietly on the vine, we continue to see small pockets of resurgence in the market for “flare launchers” or “signaling devices” in 37mm. IWA International has made an increasingly recognizable name for themselves over the years as an importer of specialty pyrotechnic devices. We previously covered their civilian-legal “flashbang” grenades and smoke grenades. More recently, they introduced the ML37, a compact smoothbore grenade launcher that’s not considered a firearm at all and can be shipped straight to your door.

The side-opening tube is more versatile than a forward sliding tube, as it doesn’t hamper the length of shell you can use.


As we said, IWA is an importer not a manufacturer. The company that actually produces the launcher is Madritsch Weapon Technology in Austria. 

A European defense contractor specializing in small arms, MWT does have an ML40 for military and police use. Based on the photos we found on their website, the ML37 appears to be identical in construction to its lethal brother, simply minus the rifling and scaled down a couple millimeters to pass ATF’s sniff test. It’s a side-opening launcher with a DAO trigger that features both a cross-bolt button safety as well as a trigger-in-a-trigger safety familiar to anyone who’s run a striker-fired pistol in the last 30 years. 

Our test launcher came as the “Full Kit” variant that includes a stand-alone frame with pistol grip, Picatinny optic rails, and collapsible stock. The stock adjustment and locking mechanism uses a unique two-part design that requires you to first depress a button and then swing a thumb lever in order to collapse or expand the stock. It’s a little ungainly to do with one hand, at least for the first couple of tries, but ensures that once you set your stock where you want it, there’s no risk of bumping it to another setting. 

The graduated offset ladder sight is the traditional sighting solution for infantry grenade launchers.

To remove the launcher from the stock assembly, open the tube and pull a single, captured pin. Then, slide the launcher forward off the frame. Closing the tube automatically presses the pin back into position, eliminating the risk of losing the pin or forgetting to lock the launcher in place before firing.

The stock frame does have a Picatinny tri-rail at the back end for mounting things like optics or lasers. The top rail is even pre-canted to compensate for the lazy rainbow trajectory of the 37mm rounds. But the included detachable flip-up leaf sight borrowed from its big brother is calibrated in 50-meter increments out to 350m, and accounts for spindrift — not that this is an issue in a smoothbore. We tested it on a 100-yard range and found the distance to be pretty well calibrated for the included ammunition.


Speaking of ammunition, we tested two types of ammo through the ML37. The folks at IWA sent us a dozen rounds of their factory flash-concussion rounds. These rounds are loaded into 4.5-inch aluminum hulls and detonate with a flash bright enough to be daytime visible even in peak desert sunlight and a bang that we’d describe as “medium volume” from the 100-

meter line. The rounds are well-made and appear to be completely sealed. The hulls are reloadable and take 209 shotgun primers. But loaded from the factory, they come in at a breathtaking $27 per round — minimum order of three rounds required.

Open the tube and pull out a single captured pin. Then, slide the launcher off its stock assembly for rifle mounting.

We also experimented with some semi-DIY “kit” rounds from FAST Ordnance. The FAST rounds are sold as component kits that must be assembled. They still use aluminum hulls, but instead of shotgun primers, the case head accepts .38 Smith & Wesson blanks — the same ones used to power Mil-spec M781 chalk rounds. In addition to one hull, FAST includes four of the .38 blanks and four reloadable payload packages. 

Available payloads are rubber batons or rubber buckshot — each with large disclaimers about not being used on humans or animals. These kits are $42.50 or $51.50 each but include enough supplies to reload it four times. 

That breaks down to $10.60 or $12.80 per round, respectively. A quick internet search showed us multiple other options for pre-loaded 37mm ammo from smoke bombs to fireworks.

Note the sloped top rail, providing a built-in ballistic drop compensation for the 37mm’s rainbow trajectory when mounting red dots.

A couple places even had contract overrun or police surplus “professional” rounds — CS, CN, pepper, etc. All for three figures per round. So, unless you have the ammo budget of a county sheriff’s department, don’t hold your breath for an opportunity to stock up on tear gas for the next mostly peaceful protest. But that’s OK. At the end of the day, this is a fun device. 

Arbor Arms makes some great soft gear, including several pieces of kit specialized for grenadier duty.

Launch colored pyrotechnics on July 4. Lob smoke grenades at your next paintball or airsoft match. Drop an old toilet downrange and see if you can blow it up with a concussion round. This isn’t a gun — of any kind — and isn’t meant to fill the practical, serious roles of one. But it’s a hell of a lot of fun. If you can afford to splurge on the ammo every so often, our advice is to check all gravitas at the door and pack this crowd-pleaser to your next open range day for a bit of impractical amusement. 

IWA International ML37

  • Caliber: 37mm
  • Capacity: 1
  • Barrel length: 9 inches
  • Price: $899


  • Telescopic Stock Frame $499
  • Picatinny Rails $135
  • Price as pictured: $1,533


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1 Comment

  • Raymond Yarosis says:

    This a nice writeup but the ML-37 will not take most commercial rounds. IWA and Exotic Firearms are the only ones who supply casing that do fit the ML-37. most commercial rounds are 37/38mm and will not seat fully in the ML-37’s 37mm bore due to the bore not being stepped.

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  • This a nice writeup but the ML-37 will not take most commercial rounds. IWA and Exotic Firearms are the only ones who supply casing that do fit the ML-37. most commercial rounds are 37/38mm and will not seat fully in the ML-37's 37mm bore due to the bore not being stepped.

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