Truly Radical Reloading: Unconventional Fodder for the 40mm Grenade Launcher

By Will Dabbs MD

Grenade launchers fall into a strange niche in advanced American gun collecting. On the battlefield, they are powerful combat multipliers. Traditionally referred to as “the platoon leader’s artillery” in grunt-speak, the grenade launcher fills the tactical gap between hand grenades and an infantry company’s organic 60mm mortars. The standard military issue M433 40mm HEDP (High Explosive Dual Purpose) rounds have an effective casualty radius of five meters and can punch through two inches of steel armor plate at a 90-degree angle of incidence, enough to penetrate the roof armor of many armored vehicles. These rounds are effective and proven in combat. Alas, however, the typical civilian shooter will never even see one in the flesh.

Despite the fact that legitimate high explosive rounds are functionally non-existent in the civilian world, there is still a powerful stigma against grenade launchers in the hands of civilians. The very notion that private citizens could own such stuff, despite the lack of explosive ammunition and the obvious dearth of grenade launcher-related crime, is enough to induce the vapors in the less durable members of our society. That was more than enough reason for me to seek one out to add to my collection. My money has gone toward stupider things in the past. Nowadays, however, there are some new street-legal rounds for the 40mm grenade launcher that will actually justify the purchase.

Really Big Guns

A grenade launcher is a Destructive Device (DD) in BATF parlance. That means it has a bore diameter greater than ½ inch. Destructive Device is the catch-all term used to define large bore guns, grenades, incendiary devices, and poison gas. I suppose how we might go about putting a serial number on poison gas is a question for another day.

Conventional big bore shotguns would otherwise fall into this category as well (the 12 gauge has a bore diameter of .72 inches, for example), but there is a specific exemption that protects these common guns. A live grenade launcher transfers as any other National Firearms Act (NFA) weapon might. Just like transferable machineguns and sound suppressors, DD’s require 2 fingerprint cards, a BATF Form 4 in duplicate, a check for $200, and that ludicrous self-attestation of citizenship.

Where a DD departs from convention is that dealers must have a DD license to transfer one. As the demand for DD’s is quite small, actual licensed Destructive Device dealers in the civilian world are about as rare as high explosive grenade launcher rounds, fiscal restraint in Washington, or liberal machine gun collectors. As a result, BATF will typically allow one or two DD’s to transfer through a conventional Class II or Class III firearms dealer per year. These transfers are always approved on a case-by-case basis, but I am living proof that it can be done.

My M203 came from Lewis Machine and Tool (LMT). Unlike the vast majority of defense contractors, LMT is happy to do business with average American gun collectors. They can help walk you through the process, and they carry a full line of M203 grenade launchers and accessories. They build stuff for professional trigger-pullers, and the quality of their products is superb.

The Hoch-und-Niederdruck System

That prodigious product of Teutonic lexicography translates roughly into high-low pressure system. The key to the 40mm grenade launcher is a brilliant bit of Physics dreamt up by the Nazis in World War II. When faced with a shortage of propellants and the necessity of delivering relatively large payloads from shoulder-fired weapons, those inspired but woefully misguided Germans contrived something revolutionary.

The key to the effectiveness of these rounds is a pressure chamber within a second pressure chamber. A modest powder charge is detonated within a small capsule located in the propellant portion of the round, and this blows out a sacrificial membrane, typically a copper disk of some flavor. The hot, high-pressure gasses then escape into a larger chamber behind the projectile. The end result is a gentler acceleration resulting in less practical recoil. In this way, a typical milspec 40mm launcher can throw projectiles many times the mass of a standard 12-gauge shot column comfortably. In practical application, it works like a champ.

40mm launchers are making a comeback in Law Enforcement. An M79 single-shot, break-open grenade launcher is accurate and about indestructible. An M203 under-barrel unit allows LE operators to maintain grenade launcher capability in concert with their primary rifle. There are a plethora of factory less-than-lethal options available to LE entities for the 40mm platform that gives the tactical commander remarkable flexibility.

Owning one of these delightful guns as a civilian requires the hassle of BATF registration and a transfer tax, and proper milspec explosive rounds are not available at any price. As such, is there really any legitimate reason to go through the pain and paperwork to obtain one of these stubby little guns? Alas, www.reloadableshells.com answers that question loud and clear.

Each of their standard rounds sports a machined powder chamber for a powder charge. These individually machined rounds accept a conventional primer for ignition and use standard powders such as Unique or Bullseye. They include a space for a consumable copper blowout disk that nicely replicates a reusable version of the original German high-low pressure system. The basic engineering behind the thing is simply inspired, and the rounds can be reloaded essentially indefinitely.

Payloads are the fun part. Massively oversized shot cups carry most anything you can imagine. Flechettes and buckshot are breathtaking, for instance, and experimentation is half the fun. They also produce massive rubber missiles replete with spin-stabilizing tail fins for precise less-than-lethal applications. They sell consumable copper blowout disks and cardboard nose covers at a reasonable price. The finished loaded product with a cardboard nose cover in place is effective and looks professional. After firing there are five perfectly symmetrical holes burned through the blowout disks that correspond with their counterparts in the chamber plug.

These guys also produce a tri-part round that sports three 28-gauge projectile chambers. In this case, standard shotgun wads can be used to fire whatever you can think of to stuff into them. All three tubes fire simultaneously via a common lift charge.

Standard adapters sleeve conventional 12-gauge rounds to the 40mm launcher. Using one of these simple aluminum devices allows the M203 or M79 to fire anything your venerable 12-gauge might. The muzzle flash from even low-brass birdshot is frankly incredible, and these adapters add low-cost utility to the platform in both civilian and LE applications. In a pinch, you could even use your grenade launcher thusly equipped to bag small game. Given that the resulting effective barrel length is maybe half an inch, you will likely not be bagging your limit on the dove field, but I doubt anybody else there would sport a cooler smoke pole. As with all of their products, the workmanship and engineering are both top shelf.

Their newest invention is so cool as to strain credulity. This shell packs four standard .410-gauge shotgun rounds into a single 40mm round and fires them all simultaneously. The round uses a conventional primer for simultaneous ignition that pushes a machined steel plate incorporating four separate firing pins. The practical applications of this little monster are limited only by your imagination.

Several companies produce personal defense rounds in .410 these days, but Winchester’s PDX1 Defender loads in .410 are remarkably capable. Pushing either three or four (depending upon whether it is a 2.5 or 3-inch load) of what the company calls Defense Disks along with a cloud of copper-plated BB shot, these Defender rounds are purpose designed to be utterly devastating close range defensive tools. Defense Disks are little copper-plated death Frisbees that fly flat side forward. The resulting mayhem downrange is thought provoking, to say the least. Now imagine launching four of them simultaneously. In the largest loading, that’s sixteen disks and Lord-only-knows how much shot. At close range, nothing else you can fire from the shoulder is even in the same neighborhood.

Taking the Beast for a Stroll

The modular nature of the design allows users to individually customize their loads. However, appreciate that this can be a serious tactical tool. These rounds plus a 40mm grenade launcher equal some serious downrange horsepower. The 40mm launcher has a bore diameter roughly twice that of a 10-gauge shotgun, itself an impressive piece of ordnance, and a commensurately massive payload capacity. The flechettes fly in a cloud while the less-than-lethal rubber baton round would be adequate to absolutely ruin your day. Buckshot would knock most anything that walks right into the dirt.

The quad .410 round is frankly unbelievable. Recoil from a single .410 round is inconsequential. Recoil from an aggregate four at once borders upon unpleasant. What you get for all that sinister physics is close-in firepower adequate to stop a marauding grizzly bear. The overall pattern stays on a man-sized target out to maybe twenty meters. At this range or closer, a single blast will literally chew the center out of a silhouette.

This is ammunition reloading and as such requires a bit of initiative and institutional knowledge. I worked up my loads balancing powder charges against payloads just like I would have on a smaller more familiar scale. It took a little fiddling to get reliable service out of the quad .410 round but once it was tuned it was unbelievable.


It seems crazy to spend as much as $100 on a single round of ammunition, but this stuff is exquisitely well made and can be reloaded essentially ad infinitum. Additionally, the allure of stuffing common household objects into the payload cup and then accelerating them to lethal velocities possesses a timeless appeal. Parachute payloads, beanbag loads, and home-rolled smoke marker rounds in addition to the aforementioned conventional buckshot and flechette varieties are easy to conjure. The undertaking is limited solely by your imagination.

As with anything firearm-related, have fun but be careful. Adhere religiously to the manufacturer’s published limitations concerning powder charges and projectile weights and physics dictates that you will not overstress your expensive grenade launcher. Working up cool stuff to throw out of a 40mm launcher makes for Saturday afternoon fun on an apocalyptic scale.

You likely have a nice AR as well as a proper tactical handgun or three already. Maybe you even took the plunge and bought a sound suppressor for some of them. When you have sated your addiction on the pedestrian iron, ponder whether or not you are ready to graduate to the truly big stuff. An operational 40mm grenade launcher is easier to procure than you might think, and reloadableshells.com will keep you well stocked with bizarre and effective things to shoot out of it.

Big bore reloading along with a 40mm grenade launcher adds flavor to even the most seasoned gun collection and these remarkably innovative rounds render the platform genuinely useful for both Law Enforcement users as well as civilian big-bore enthusiasts. Even if you have been pulling triggers and reloading ammo all your life, it is a fair bet that you’ve never played with anything quite like this. Reloadableshells.com brings the 40mm grenade launcher to life.


This article first appeared in Small Arms Review V21N1 (January 2017)
and was posted online on November 18, 2016


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