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LMT M203 Grenade Launcher: Pull Trigger Go BOOM

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Article first appeared on Ammoland.com

USA –-(Ammoland.com)- Last month we hinted at a super nifty add-on for the Brownells BRN-601 AR-15 Rifle that one of you is about to own.

The Brownells BRN-601 Rifle is a reproduction of the very first AR-type rifle ever issued to the US Military. While the basic design features are the same as features on today’s modern sporting rifles, you’ll notice the classic details like a fixed stock, green furniture, triangular charging handle, and duckbill three-prong flash hider. For all the details, check out our review here.

Here’s the thing. A rifle like this is awesome, but we felt it needed a little authentic accessorizing to make it epic. A little flash and bang so to speak, with emphasis on the bang part. Enter the Lewis Machine and Tool Company M203 37mm Grenade Launcher. Yes, it’s legal to own and requires no NFA paperwork or tax stamp, but be sure to check your state laws to make sure there are no issues. That’s because it’s permanently modified to fire 37mm flares, smoke, signaling, and inert rounds rather than those 40mm high explosive grenades that most homeowners’ associations frown upon.

LMT M203 Grenade Launcher

LMT M203 Grenade Launcher
LMT M203 Grenade Launcher

Let’s take a closer look at this little nugget of freedom on steroids.

LMT M203 Grenade Launcher History

The M203 Grenade Launcher is a love child of the Army’s Special Purpose Individual Weapon project. Invented in 1969, it went into service in the early 1970s. The M79 stand-alone grenade launcher actually predates the M203. If you will recall the resident platoon badass in old Vietnam war movies, the M79 is the launcher with a wooden buttstock he carried along with bandoliers of 40mm grenades. The raison d’être of the M203 was that an average human really couldn’t carry a full M79 and ammo load, a rifle, and adequate ammunition supply, so that guy’s flexibility was limited. The M203 allowed any rifle-equipped soldier to have grenade capability for use when appropriate without losing a rifle in the team’s overall firepower.

The original M203 was designed for attachment to an M16 rifle, but later versions like the M203A1 and M203A2 offered longer barrels, up to 12 inches, and the ability to mount to a standard M4 carbine.

LMT M203 Launcher Specs

The folks at Lewis Machine and Tool have created an exact replica of the M203 grenade system, but with a few design tweaks to make it “street legal” so to speak.

The LMT M203 launcher installed on the Brownells BRN-601 AR-15 Retro rifle.
The LMT M203 launcher installed on the Brownells BRN-601 AR-15 Retro rifle.

This M203 uses a 37mm smoothbore barrel. The original explodey model used a 40mm rifled barrel, so this replica is completely incompatible with the highly regulated explosive ammo for the military version. Don’t worry about feeding this beast; however, there is a wide variety of legal ammunition available. We’ll get to that in a minute.

The M203 is a single-shot launcher that operates kind of like a break-action shotgun. A release button on the left side allows the chamber and barrel to slide forward so you can insert a round into the breech. Once you add the round, just slam the barrel back into place just as you would cycle a pump shotgun and it’s ready to fire. The M203 is “part of a shotgun” and leverages some of the rifle’s components to operate. For example, there is no pistol grip for your firing hand – you use the rifle’s magazine well for that. The unit has a trigger and a grip area for the support hand.

The LMT M203 is made from 7075 aluminum and measures 15 inches overall, including the 12-inch smooth-bore barrel. The grenade/flare launcher adds three pounds to your rifle weight when installed. If you order this unit, you must also acquire the correct mounting kit for your specific rifle. In this case, we’ve already mounted it on the BRN-601 AR-15.

Since the trajectory of grenade rounds are more like bricks than bullets, the standard rifle sights are of no use when flinging 37mm shells. No worries, there are solutions to get you on target with reasonable accuracy.

The M203 mounting kit includes a flip-up leaf sight that works in conjunction with the standard A2 front sight on the M16 or in this case, BRN-601 AR-15 rifle. The leaf has graduations in 50-meter increments ranging from 50 to 250. To use the sight, just line up the appropriate leaf notch with the front rifle sight, and you’ll be close. Of course, you’ll need to “zero” with different ammo types, so you know how each behaves.

The M203 operates like a cross between a pump and break-action shotgun.
The M203 operates like a cross between a pump and break-action shotgun.

M203 37mm Ammo

So, you obviously can’t buy or fire high-explosive ammunition with the LMT M203 377 launcher, but that doesn’t mean it’s not a hoot to shoot. There are a variety of legal ammo options from folks like American Specialty Ammo you can buy ready to go. Or, if you’re adventurous and will be using your M203 frequently, you can load your own.

You can get a wide variety of 37mm ammo like this sample pack from Exotic Ammo.
You can get a wide variety of 37mm ammo like this sample pack from Exotic Ammo. IMG: exoticammo.com


The M203 is a perfect platform for launching aerial flares. OK, so this setup may not be practical, or Coast Guard approved for your boat safety tool kit, but it sure is cool, especially at night. Be careful; flares can set fires, so choose your shooting range with care.


If you have a safe, and very fire-resistance place to shoot, you might stock up on some smoke rounds. While they don’t explode, they do burn to produce the smoke effect down range, so be very, very careful [fire, fire] about where you shoot these.


There are a wide variety of signaling and concussion rounds available for your 37mm M203. In this category, think fireworks. Starburst? Sure. Comets? No problem. Concussion fireworks? Yep, that too.


Launchers like this are used by military and law enforcement units for things like riot control as they fire “inert” projectiles like rubber slugs or balls, bean bags, wooden slugs, or even foam plugs. For the recreational shooter, these types of rounds can be ideal for target use, and they present no fire risk down range.


If you want to get adventurous and maybe reduce your per-round 37mm ammunition cost, you might consider investing in reloading supplies. Once you acquire the 37mm hulls, you can reload the primers using standard 209 shotgun primers. What goes inside is up to you, but for safety, stick to published load recipe information.

Here’s the bottom line. Welcome to America! No, you can’t add a real grenade launcher to your rifle, but you can legally get this LMT 37mm M203 and launch non-lethal projectiles, flares, smoke rounds, and even fireworks. Make sure you enter to win this rifle launcher package at the links at the top of the page.

Why you ask? Why not…


Tom McHale is the author of the Practical Guides book series that guides new and experienced shooters alike in a fun, approachable, and practical way. His books are available in print and eBook format on Amazon. You can also find him on FacebookTwitterInstagram, and Pinterest.

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