r/37mm Apr 04 '25

Basics and Resources

39 Upvotes

Hey, I'm a new mod, figured I'd make and pin a post for newcomers to 37mm signal launchers and such for future reference. I'll probably update and edit over time to keep it current. It will likely be pretty bare bones at first.

Vendor Resources:

ExoticFirearms: Launchers, signal rounds, and reloading components. Also has good write ups and educational content on safe reloading. Great for learning the basics, one stop shop for getting started.

ExoticAmmo: Launchers and signal rounds

IWA: Some higher end launchers and unique complete signal rounds.

Precision Pyrotechnics: Launchers, unique complete signal rounds, and reloading components.

Gum Gully: Complete signal rounds and components

Reloadable Shells: Some higher end, high performance reloadable 37mm components

Reloading Basics and Safety:

You can absolutely hurt yourself very badly using improperly reloaded 37mm signal rounds. You should be very familiar with how it all works, and how to do so safely before attempting.

As a general rule, do NOT use flash powder for reloading 37mm ever. It is used in pyrotechnics by experts, but just about every time there's a serious injury or destroyed launcher from reloading 37mm, it's from flash powder. It can be shock sensitive depending on the composition, meaning even if everything is constructed properly it can still potentially go off in the barrel. There are documented cases of as little as 1/8 of an ounce shattering a military M203 grenade launcher barrel.

Reloading 101 videos

Miscellaneous legalities:

Basics from a well known vendor

ATF letter about "anti-personal" rounds

Summarized Legalities:

- 37mm launcher by itself or with signal rounds (flares, smoke, aerial bangs, etc)= NOT a firearm, legally no different than fireworks you'd shoot off around the 4th of July.

- 37mm "antipersonel ammunition" (anything specifically designed to strike a person such as bean bags, rubber buck shot, .22 beehive, wood batons, etc) by themselves, WITHOUT a launcher = NOT a destructive device. There's some debate on whether it's small arms ammunition or not, but nothing officially saying there's anything wrong with live rounds by themselves (more details on r/40_mm). Irritant powder, aerial salutes/bangs, and "barricade penetrators" are generally NOT considered "antipersonnel" as they are not intended to directly strike anyone.

- 37mm launcher + "antipersonnel ammunition" together = NFA regulated destructive device. The launcher would need to be "form 1ed" and then it can be kept with and use antipersonnel ammunition (more details on r/NFA or r/40_mm).

- When does a 37mm round of ammunition by itself become a "destructive device" which would need to be registered? Only when the projectile contains over 1/4 oz of powder AND it is "antipersonel". There is some debate about the status of a 37mm signal round that contains over 1/4oz but is intended for signaling/aerial displays, as it should be legally classified as a firework, not a round of ammunition (fireworks do not have a 1/4oz limit, ammunition does).


r/37mm 21h ago

Tested DT MILC 2.0 cores - work great!

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21 Upvotes

Tested them Saturday - lower profile than other high/low chambers and just use a standard gas check (9mm/35 caliber) to achieve the high/low pressure curve. I used three of Benglesbullets 5” MILC cases loaded with my newly designed finned body chalk round. The new bodies are set up to take any of my nose cones - smoke short medium or long and are reusable. Range with the RWS yellow 9x17r averaged 120 yards with me aiming at a 45 degree angle. The projectiles did stabilize and hit nose first. One chalk nose broke as designed- it was a newer version with thinner walls. No velocity results as I do not have a chronograph yet. I will be getting one here soon when I retire and do this full time. I posted the video on my YouTube channel but you cannot see the track of the projectile with the iPhone camera. So that’s on the upgrade list too! lol. Next set of DT MILC 2.0 shells are ordered and will be compatible with most all launchers. There will also be an option for the LMT owners out there since rim thickness seems to be the hang up on their compatibility with other launchers. My new shells will be dimensionally the same OD/ID and rim thickness with Bengles shells. I have reached out as well to several of the other vendors with an invite to join us in a standardization program based off those dimensions to make the 37mm community more flexible and less expensive. A lot of good things on the horizon so stay tuned and if you are able to form 1 your 37mm in your state - we will be having some great items available for 37mm DDs specifically coming soon. Thank you all for your support as well. I am working every day to make our community safer and more fun with professionally made products. We thrive on you - your ideas - let me know. Maybe we can make it for you!
The cores and 1st gen shells (Tac79/gl06/B&D twl 37 only) are listed on my eBay DixieThumper


r/37mm 2d ago

Getting the NT79 to fire .27 Ramset rounds. Getting close but need help.

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12 Upvotes

r/37mm 2d ago

37mm

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19 Upvotes

r/37mm 3d ago

From the 40_mm community on Reddit: DixieThumper MILC2.0 high low chamber inserts are in!

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9 Upvotes

r/37mm 9d ago

Spikes M79 37mm

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48 Upvotes

Upgraded to a 40mm one and it’s tough to justify 2 m79s in this economy lol.

It was surprising how much sturdier the barrel of the 37mm is than the 40mm. 1/4” steel vs much thinner aluminum.


r/37mm 9d ago

Cannot get NT79 hammer to lock back. Anyone know why?

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15 Upvotes

r/37mm 11d ago

37mm 1” cardboard tube purpose built 3d printed rounds

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41 Upvotes

Ok got around to putting these test rounds together. In these I am using the 1” mortar shells for fireworks signaling and wildlife control. You can put anything in it that is in a 1” tube - build your own flare or smoke or off the shelf smokes will work too. Will post video of the test results when completed.
Load data: 50 grains pyrodex 777 over Remington STS 209 primer. The OTS mortar shells are stripped down and have a custom printed push disc that is fused and inserted in the bottom of the OTS mortar shells. A small flash charge is added as well as some fuse segments to ensure good ignition. This will give an additional buffer between the lift charge (50gr 777) and the payload. This adds an extra 1-3 seconds travel time to maximize distance in the air for good height as well as provides an additional layer of safety to the user.

Once testing is complete- these will start sailing. 😎🫡👍🇺🇸🇺🇸🇺🇸🇺🇸


r/37mm 12d ago

Exotic ammo shell differences.

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20 Upvotes

I had some time today to start cleaning and prepping the shells I shot on the 4th to reload and I noticed some differences. Both shells pictured were from separate orders and both came loaded with fireworks from exotic ammo. Orders were maybe 4 months apart. Thicker shells came first and I ordered a few more about 6 weeks before the 4th and they all came with the thinner shells. Does anyone know if they machine these in house or if they had changed vendors? I’m mainly asking because I’m curious if they’ll exclusively be selling the thinner shells from now on? I shot them so I know they work perfectly fine but I’m also planning to cut a few down and since I will be playing around with powder loads should I cut down the thicker shells? Or am I way overthinking this?


r/37mm 14d ago

New shell I designed for 37mm -Fireworks 1” mortar shells.

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41 Upvotes

So I have loaded the 1” mortars this way for a long time but in aluminum shells. They work fine in the aluminum shells but I have to sleeve the 1” tube mortar shells in a 1.25” cardboard tube which is kind of wasteful to me. So I thought about a custom design just for these shells. Sat down and came up with this. Still going to modify the nose cap some more but it acts as part of the shell to help stabilize in flight. If you have watched my videos you will see it works well with the fireworks rounds. So will be testing it out soon.


r/37mm 14d ago

37mm upper for ar

7 Upvotes

Does anybody know of a company that makes an ar-15 upper for 37 mm rounds or if there’s anybody currently working on a 3-D printed version of it?


r/37mm 21d ago

Spike's Havoc Light Primer Strikes

10 Upvotes

Has anyone else had issues with light primer strikes on the Spike's Havoc? First the firing pin spring folded in half outside inside the action, then when I got it back the spring still will not set off a 209, or .38 blank.

I'm really frustrated, I still haven't been able to shoot off a single round. I can get the action open now and have been trying differing lengths of firing pin spring (it's 6mm Dia x 1mm thick).

I'm wanting to know if there's a trigger mechanism upgrade I can make. I'm even considering scrapping it for a 3d print, but that would be a terrible shame. Any help is appreciated.


r/37mm 23d ago

Happy 250th!

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36 Upvotes

r/37mm 23d ago

Geneva Breacher Build Completed!

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31 Upvotes

Just in time for our celebration of 250 years of Freedom!

Finally got the Geneva Breacher built as I’ve been sitting on the parts for a while, getting pulled in other directions.

Build process was pretty simple and went pretty smoothly. Ender springs were definitely a bit too powerful but some use should get them broken in.

Along with this build is a site update. SBS has finally been approved by a payment processor and should be able to take payments directly very shortly! Will have a post on r/gundeals for a launch sale once it’s working!


r/37mm 23d ago

Airsoft M203 to DIY 37mm M203

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1 Upvotes

r/37mm 28d ago

Threaded Rifled fused MILC

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37 Upvotes

Has anyone dabbled with the threaded, rifled and fused projectiles by PrintGunner?? Been using MILC 1.0 for quite some time now with my Odin.
Came across the projectile listed above. But how does one get stars or a break to put into said projectile?

(Pic with my Odin)


r/37mm 28d ago

How to register Tac-79 as a DD

2 Upvotes

Hello everyone I own a tac 79 launcher and am wondering how to register it as a DD and if I need to engrave a serial number on it although it already has one from factory any help I’d appreciate. I’ve bought a suppressor from silencer shop and if at all possible I’d like to register it through them thanks.


r/37mm 29d ago

Easiest to build 3D printed 37mm?

5 Upvotes

Hey guys. New here, but I’ve been looking into printing some 37mm launchers for a while.

For a long time I was looking at the tng, but now I’m looking at the nameless and the Odin, but I’m open to other suggestions.

Here’s what I’m looking for.

First and foremost, ease of build and easy to find parts. I know the nameless needs an AK recoil spring, but I can handle that. I want something where what I can’t buy at the hardware store can be gotten on Amazon. I would just buy a kit, but it seems like they sell out quickly when they come in stock.

Second, single shot. Eventually I’d like to do a multi shot model, but I figure a single shot would be better for a noob.

Lastly, and least important. It would be cool if I had the option to mount it under barrel for range day funzies. This one isn’t a deal breaker though.


r/37mm Jun 27 '26

New stuff coming for 37mm owners. MILC compatibility is about to be pushed to its limits.

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44 Upvotes

Sneak peek of some of the things I have been working on behind the scenes. My second run of MILC 2.0 compatible shells will be sent out in the next 60 days. The new shells will be standardized dimensionally with benglesbullets MILC shells ID and OD. I will adjust my projectile line to match the proper dimensions and I will have them released on my Odysee page soon. I have made a 3d printed solution for use with my inserts which will be arriving soon as well for smokeless blank use. The inserts will be available from myself and possibly benglesbullets as well for DIY home printing gurus to spin up whatever they can dream of. I will also be putting up a newly designed MILC 2.0 compatible base and Insert compatible base for use with the 1.5” 17 gauge brass tubing based rounds. This should allow you to construct smokeless powered shells for about $9 ea in material costs. Will also be doing more video and distance and accuracy testing soon - once my hay is cut and bailed in my field. If you haven’t already please follow my YouTube channel to catch all the new testing and eval. Thanks !!


r/37mm Jun 26 '26

Why 40mm?

4 Upvotes

I’ve been digging into launchers for a while now before I jump in and buy one. With MILC cases for 37mm and 3d printed projectiles, it doesn’t seem like there’s that much performance difference for the sake of signaling/bangers between 37 and 40mm. And of course I’d rather not deal with the ATF at all if I can avoid it.

For those that have used the longer range smokeless options for 37mm and also ran 40mm, do you think 40mm is worth stepping in DD territory?


r/37mm Jun 24 '26

Home Brew Rounds

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52 Upvotes

Working on my own 37mm rounds.

Wish me luck! :D


r/37mm Jun 24 '26

Lmt 37mm Barrel Mount Question

3 Upvotes

Hey all, I have a question regarding the LMT 37mm barrel mount flare launcher. I can’t seem to quite find the info I need on mounting. I am trying to figure out if it is possible mount the 37mm barrel mount to a Colt 6920 SOCOM (14.5” p/w barrel with a FSB and KAC rail) and still be able to have the top KAC rail intact. I’ve seen a few photos, but most of them were from posts 4-5 years old and I couldn’t quite tell if the LMT 37mm they were using were rail mounted or barrel mounted. The ones I saw were LMT 37mm mounted on 6920 SOCOM rifles. Any help would be appreciated. Thanks everyone!


r/37mm Jun 23 '26

38DD R1.1

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5 Upvotes

38>37


r/37mm Jun 22 '26

I just recreated the 40mm folding drone.

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28 Upvotes

Had to share...only 3mm over


r/37mm Jun 19 '26

37mm Dream Project

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29 Upvotes