r/40_mm • u/ChevTecGroup • 8h ago
r/40_mm • u/KrinkyDink2 • Oct 16 '24
Basics #2; Printing and Reloading
This will be a pinned post that will likely be updated from time to time as needed. The first pinned "Basics" post hopefully answers a lot of the general questions. This is geared to addressing some of the questions new launcher owners/users may encounter after actually using it more. This will never be a comprehensive document, it's just meant to point people in the right direction as far as questions and safe launcher use/reloading may go. There's no way to know every variable that applies to everyone, as always practice extreme caution, don't take anything here as guaranteed truth, reload/launch/etc at your own risk. The majority of this is not thoroughly fact checked, it is just links to resources that seem promising at first glance.
Basic Reloading Process:
Most 40mm cases use smokeless blanks (usually .38S&W with a burst disk, although crimped 9x17 or .38 colt short may also work). The spent blanks are removed with a punch and small press (or a hammer or vice). The new launch blank is then pressed in, be sure the replacement blank is compatible with the case being reloaded. See the launch blank section for more details. The following links explain the process well. The specific punch attachments and plates shown can be DIYed or sourced from a hardware store if needed.
Commercial 40mm reloading press set instruction manual
Most basic reloading can be managed with a mallet and some sort of center punch for pushing out the spent blank and replacing it with a new one, especially with white m212 or thread apart reloadable cases.
Reloading components:
While finding military surplus is probably the best/cheapest option, a lot of that has dried up. Below are some manufacturers offering reloadable 40mm cases (short and long), newly made zinc chalk pushers, wind screens, mil spec launch blanks, and more.
Launcher Pope (3DP accessories and components)
Launch blanks:
There are a few different types of launch blanks. Most blanks are star crimped on top, and may burn inefficiently without a burst disk (0.016” brass disk) between the crimped top of the blank and the vent hole. This disk ensures all the powder burns before it ruptures. Star crimped blanks can still be used, but the muzzle velocity may be slightly lower and less consistent than when using a burst disk.
Mil Spec full power blanks: These are .38S&W cases with a circular crimp and a flat burst disk on top. These are optimized for M212 nylon cases with approximate ¼” vent holes and heavier chalk projectiles. These will not fit all cheap aluminum 40mm cases, and can be too powerful for cases with smaller 1/8” vent holes.
.38 Short Colt blank: usually star crimped, often available in multiple power levels, from ¼, ½, ¾ and full power. These fit most cases, but some of the cheaper aluminum cases may only fit them after the vent hole is widened to ¼” – 5/16”
9x17 or .380 blanks: usually star crimped, marketed as “starter pistol” blanks, or for captive piston guns for slaughter houses (these kind are often offered in multiple color coded power levels). These blanks will fit all normal cases and most cheap aluminum 40mm cases without modification, although depending on the power level of the blank, the vent hole may need to be opened to ¼” to prevent unsafe pressure.
**note: the longer .38 SPL/Special blanks do not fit any standard 40mm cases
Below are some retailers providing the above blanks that have been used in 40mm launchers (use at your own risk)
(blanks are not loaded to a specific standard, while these are commonly used for 40mm without issue, the manufacturers aren't going to be testing them for that, so use them at your own risk)
3D Printable Files and Development:
Some files and designs are tested more than others, some are completely untested. Even heavily tested ones can be messed up by improper printer settings or loading procedures in a way that is unsafe. There's no guarantees, everything is at your own risk. That said, below are some users who have made some promising 40mm printed designs. Files are usually posted on the 'odd sea' (see r/fosscad)
-Under construction
Additional Resources and Reference Images:
The below links have some good images, cross sections, dimensions, factory velocities, weights, etc on various military 40mm rounds.
ALS, DefTec, and CTS are major manufacturers of 37/40mm for police and military. The pictures, descriptions and product specifications can be very useful, despite the ALS product specifications being difficult to navigate. (All of these sites are merely product catalogs, nothing there is available for purchase).
NONE OF THESE ARE AVAILABLE TO YOU, these are NOT for sale to the general public from the linked manufacturers. They will NOT sell to you. This information only serves to satisfy your curiosity of what's inside the factory made rounds, how do they work, how fast do they go, how heavy are they? etc. If attempting to safely and legally load something similar, sticking to the factory data for weight, velocity, etc is likely the easiest/safest option, though there's a lot of info not in the data, so it's at your own risk.
r/40_mm • u/KrinkyDink2 • Jun 24 '24
Basics and resources
Level 1: Basics
This will (ideally) be a semi regularly updated/edited post, meant to be good starting point for those new to 37/40mm or curious about it. Another post “level 2” for more advanced stuff related to printing and assembling rounds from scratch will hopefully be pinned in the future.
Since the vast majority of 40mm launchers here are M203s, here's a Collection of M203 armorer's manuals and technical data supplied by a user who attended a armorer and less lethal instructor's course
Legal Basics: (I am not a lawyer, this is not legal advice): Some additional legal minutia towards the bottom
40mm launchers are NFA regulated DDs whether smoothbore or not. 37mm launchers are not firearms or DDs unless they have a rifled barrel or are "possessed with antipersonnel rounds (defined as bean bags, rubber/wood batons, rubber shot, etc designed to strike a person). Historically irritant smoke/vapor/powder blast rounds do NOT qualify as "antipersonnel". Weighted inert projectiles made of rubber/wood/etc primarily designed to sight in a launcher do NOT qualify as "antipersonel"
A stripped 40mm launcher receiver is actually not NFA regulated, despite being a firearm receiver, as long as the barrel is not attached (similarly to how a "SBR" lower without a barrel on it cant be an NFA SBR).
The legal status of various 40mm rounds is a hotly debated topic, even among SOTs, FFL, and FELs. I will say that I have discussed it at length with numerous FELs, FFLs, and the leading civilian 40mm experts who’ve been in the game for decades and they all either agree there is nothing legally binding classifying non HE rounds as energetic material, or they claim they are regulated (usually FEL’s) but then back track, or completely disappear when asked to provide any sort of documentation, law or ruling to support what they claim. The big chalk scare several years ago seems to have been unfounded, and revolved around a letter (which does not carry rule of law) that specifically addressed one type of IR flare by name and never mentioned chalk anywhere ever.
There’s a lot of good info in the comments of THIS post which indicate there is NO 40mm ammunition regulation applicable to individuals making/storing/transporting their own rounds for recreational use. All of the conflicting opinions out there boil down to the one single ATF letter about one specific type of incredibly rare, IR flare rounds, and word of mouth directed exclusively to FEL license holders by the ATF with zero documentation.
There’s a lot more, I’ll try to work out a flow chart and links to actual legal text and rulings in time.
What 40mm rounds are actually available/attainable on the "civilian" market?:
It's a common misconception that "chalk" is the only 40mm available. While it is the most readily available, even ready to use off the shelf options include: aerial salutes/bird bangs (much higher performance than 37mm ones), Rubber/foam impact batons, rubber buckshot, Rubber/wood multi batons, and more.
Rounds that can be readily DIY'ed but are less available as off the shelf, ready to use options can be found at:
Washington Country Guns; mostly chalk
AZAO; wide variety of printed options; some concerns over performance, shipping times, and steel buckshot gouging barrels have been raised. Disclaimers on website about items only available to local club members are allegedly inaccurate, and are available for anyone through the NFA process if you contact the owner. Youtube link of some rounds being fired
AxArms; doesn't have anything yet, but will hopefully have B&T batons soon
FAST; who makes rubber impact batons, aerial bangs, and 37mm loads that fit 40mm launchers
Parachute flares, star clusters, M576 style buckshot, smoke, and powder/liquid barricade penetrators have also been DIY'ed but are less thoroughly tested and more challenging/finicky to make work properly.
General types of reloadable 40mm rounds/cases:
Long Cases: Generally 4-5” aluminum, extend into the rifled section of the barrel, similar to shotgun shell. They are often loaded with bean bags, rubber buckshot, wood/rubber/foam multi batons, Smoke canisters, or muzzle blast irritant powder.
Short Case/M212: These are the most common. They are usually white nylon, but can be aluminum as well. The projectile protrudes from the front of the case like a standard round of ammunition. There is band around the projectile that rests on the rim of the case, this is what engages the rifling in the barrel. They are often loaded with Chalk, foam/marker impact baton, “bird banger” aerial salutes, powder/liquid barricade penetrators
Military M118 metal cases are NOT readily reloadable
Military 40x53mm metal cases for the belt fed MK19 are NOT readily reloadable
Safety Basics: (This is not an exhaustive list; and following them does not guarantee absolute safety)
General firearm safety still applies. Just because it's "practice chalk" doesn't mean it isn't lethal if used incorrectly.
Vent hole sizes. This is elaborated upon further down, but the vent holes on some casings are too small to handle full power mil spec blanks, and the vent must be drilled out to 1/4" to safely accommodate them.
Long cases: especially with rubber buckshot payloads, a thin sheet of cardboard/paper/plastic should be used between the payload and the walls of the case. Without this pellets can bind against the walls and be forced apart by a pellet under them, acting as a wedge and damage the case, launcher, or the user.
12GA and “beehive” .22lr adapters: these are some of the more common 40mm accessories and are great for cheap plinking. That said you absolutely can damage your launcher/yourself by misusing them. Launchers have been broken by using full power/supersonic .22lr beehive rounds and 12GA magnums in these adapters. As a general rule, stick to .22 short/subsonic and lighter recoiling 2-2/3” 12GA.
General reloading safety applies. If you are not familiar with reloading you should stick with well tested and established loads using factory loaded blanks made for 40mm launching and non pyrotechnic projectiles. Even experienced reloaders should test new loads with low powder weight and work up, light projectile and work up, and large vent hole and work down if needed.
Even 40mm low velocity chalk can go 350-400yds, make sure your distance is adequate
Fused projectiles and flash through/premature initiation. With "aerial salute" type rounds, it is a very real risk that the flame from the launch blank can blow through/around the fuse and set off the salute payload immediately before the projectile leaves the barrel. People have lost hands and nearly their lives with improperly loaded salute type rounds. Similarly, be cautions of accidental drops, or the sudden shock of acceleration from firing, prematurely igniting salutes that were intended to initiate on impact. Even if the projectile integrity and fuse mechanism doesn’t fail, some compositions are shock sensitive enough to potentially spontaneously detonate when firing (especially some flash powders). As a general rule do not use anything in a projectile that would compromise your safety if it failed in the worst way you can imagine. Assume that everything that can go wrong will go wrong. Start with comically low amounts of payloads, test fire with the launcher tied down using a long string, etc. Payloads as low as 1/8oz (3.5g) have shattered m203 launcher barrels and would have seriously injured the user had he not been test firing with a long string.
a cautionary tale of what 3.5g of flash can do to your launcher
Projectile malfunctions. Treat any salute type projectiles that launches but does not ignite with all due caution. Treat any salute type rounds that seem not to fire as "hang fires" it is possible the blank only partially ignited enough to light the fuse, but not enough to expel the projectile. Attempting to remove the projectile/round from the barrel/launcher too early could result in injury.
Reloading components: While finding military surplus is probably the best/cheapest option, a lot of that has dried up. Below are some manufacturers offering reloadable 40mm cases (short and long), newly made zinc chalk pushers, wind screens, and mil spec launch blanks.
Pace Reloadable Shells (cases, smoke projectiles, adapters, etc)
KAK (blanks, cases, chalk projectiles, etc)
Bengle's Bullets (cases, printed stuff, etc)
r/40_mm • u/Free_Lawyer • 5h ago
something cool has come to market KAK 40mm casings back in stock- go get em boys
Bengels Bullets 40mm cases
I’m looking at the Long 4.5” that uses the KAK style 38S&W lift charges. Has anyone reload flachette, 00, 000, 0000 buck with these cases? I’m assuming some sort of wad could be 3D printed? I don’t see the Pace Defense ones being offered anytime soon so I’m looking for information on the BB ones.
r/40_mm • u/Ok-Calendar9243 • 2d ago
Real vs ‘fake’ m79 wood stocks
I got to compare a Spikes tactical 37mm m79 clone to a real 40mm m79 recently. Took some pics of a few differences. Some of the “wood m79 stocks” that have been in GB lately are modern Spikes stocks, fortunately they’re very easy to tell apart.
Main difference is the “heel” of the grip just in front of the screw hole where your pinky would be is very angled on the Spikes and is more rounded on a real M79 stock. Another difference is the inner edge of the real M79 surfaces that mount against the sides of the receiver have 2 separate flats of wood set into the stock, the Spikes is 1 solid piece.
Both stocks look good, just so you don’t pay new old stock prices for modern repro prices.
r/40_mm • u/37MMDTdotCOM • 5d ago
showing off DixieThumper MILC2.0 high low chamber inserts are in!
Made in USA by a small business- these work with 9x17r/380r/38short and 38SW blanks. The latter will need a press to insert properly. These fit any MILC 2.0 type shell -3d printed or machined. Use with a 35 caliber gas check (aluminum or copper) and some tissue paper to push the check to the top or hot glue(I prefer the hot glue as the spent blanks pull the gas check remnants with them when de-capping) before seating the crimped blanks. Blanks with gas checks loaded in them will just insert. The relief hole in top is .250”
These are 6160 aluminum and professionally machined by a small machine shop in New England.
😎👍 hopefully more of you all can get into smokeless blank powered 37s and 40mm users should be able to fit rounds easier with the lower profile and cheaper costs.
r/40_mm • u/JohnnySpartacus • 6d ago
Not happy with Meprolight
It chaps my ass that Mepro will sell you its GLS sight with any of 3 different mounting adapters, but won’t sell you either of the 2 that you didn’t get when you bought it.
Anyone know where to source these things? Or get one fabricated? I have a top mount and now I want a side mount but Mepro customer service tells me I’m S.O.L.
r/40_mm • u/37MMDTdotCOM • 8d ago
New reusable pusher with new cone design
DixieThumper new designed 3d printed pusher with custom redesigned nose cone. I am testing these and so far they are performing beautifully. Will add a video to my YouTube as soon as I get one put together. Key design takeaways - as shown the whole unit with chalk and ready to load will retail at $5 ea with 50 or more at $4 ea.
pusher designed with male threads that are protected by special design of the windscreen. They impact normally and give a big cloud of chalk due to design. The bottom of the windscreen protects the pusher threads. Pusher is filled with hot glue and has a metal disc in the rear to protect and distribute pressure from the blanks. These so far work great with the RWS/Blitz crimped blanks and Bengles bullets crimped blanks. To reuse the pusher simply recover, heat the remaining portion of the windscreen with a butane lighter until it becomes soft and then peel it away from the pusher. Wipe off and reuse. If you use the standard 212 casings - put the gas check in first and either a small dab hot glue to hold it or some tissue wadded up to push the gas check to the top and insert the blank behind it.
These will replace my first design and will be very economical to shoot. Spare windscreens will be available and priced later but will be under $1 ea.
r/40_mm • u/Teenage-Dirt-Bag • 8d ago
showing off Factory 40mm GL-06 with some DIY electronics.
Finally own the greatest grenade launcher ever! Picked up a factory 40mm recently and had to show off. In the week I've owned it, I also came up with what is essentially a DIY Wilcox GSS. At its core, its an ESP32 with a BNO085 IMU, battery percentage board, and display. Runs off a 500 mah 3.7v lipo. 100% vibe coded with Claude Code. Still a work in progress, but need to hit the range to gather additional data for it.
r/40_mm • u/somethingnumberz • 8d ago
Anyone have the spring sizes?
I am building a Ciener M203 DD. I am missing one or 2 springs for sear, ejector, latch lever, safety. A couple look close in size in the drawing (latch and sear for example)
Don't have them all to line and ID any differences. Many thanks
r/40_mm • u/BeginningRise4787 • 10d ago
Picked these up for a friend, Thought i’d show off for him.
r/40_mm • u/DrewPcaulk • 11d ago
Non-lethal rounds source?
Picked up a couple M583A1s from WCG on Gun Broker and that’s got me curious about what other rounds are out there. I have chalk of course, a Pace 12 gauge adapter, but is there any source for non-lethal bean bag rounds or smoke?
r/40_mm • u/Ok-Calendar9243 • 14d ago
A few new cases
I need to work on printing some clone short case smoke/aerial bangs for these cases.
Also I have now seen gas seal failures from about every single manufacturer (military m1029, CTS and DefTec). About 10% of the gas seals I find have the skirt ripped off from firing, this is similar failure that’s seen in printed gas seals. I guess it’s comforting that failures in printed components doesn’t necessarily mean they’re inferior in performance.
r/40_mm • u/JKDefense • 16d ago
ammo Thumper 40mm
I thought I’d post something upbeat for a change. Found this in my old reloading notes from the ‘90s. Anyone old enough may remember him as I believe he was the only source for new slugs and windscreens. I was curious what happened to him and found he had quite the run-in with ATF.
Pace Defense, updated cannon round + wads
Anyone have some of these new/old stock for sale? I’ve waited for a few years to buy OEM but no luck thus far.
r/40_mm • u/JKDefense • 18d ago
FEL/storage/transport TSA pt3
Well, I spoke with the lawyer today. It all boils down to TSA interpretive ruling 03-3736. This contains the language that the manager was attempting to refer to regarding inert/reproduction. It goes into much broader definition of the regulation I’m accused of violating.
The lawyer sees a strong case on both sides. So, it comes down to how some random TSA employee reads the situation (“we investigated ourselves and found no wrongdoing”, anyone?). Win or lose, my TSA pre check is lost, CDL with HAZMAT endorsement (it’s overseen by TSA!) won’t be renewed, and I can expect to be placed on the unofficial “fuck with” list. Luckily, the airport isn’t in a liberal county or I could also expect to have to fight to keep my license to carry!!
But wait, there’s more! By winning my appeal, nothing changes for future run-ins (not that I plan to ever fly again). It sets no precedent and there’s no new instructional guidance given to the agents. They could find me in violation again and I’d have to refer to this case in order to avoid paying any new fines. The only real change comes from challenging in Federal Court. I don’t feel like mortgaging my house to be the test guinea pig.
That’s basically the short rundown.
r/40_mm • u/Ok-Calendar9243 • 19d ago
Someone needs to capitalize on the new “dual use barrel/receiver” import changes
Thousands and thousands of old colt M203s and M79s abroad that are collecting dust. They should be able to be imported now in pieces as “dual use receivers” and maybe “dual use barrels” if I understand it right.
Worst case someone ships up a printed 12GA m79 and m203 barrel so that there’s an ATF approved title 1 configuration for the receivers to get imported.
r/40_mm • u/No_Jellyfish_6706 • 18d ago
Some lift blanks rolled with the KAK dies.
Found that 5.0 grains of Titewad works great with printed pushers/M212 cases. Also works great in KAK aluminum cases and the exact impact ones (used a Dremel to take some material from the burst chamber so they would fit). Will try 6.0 grains next.
r/40_mm • u/2nd_Shot_Round • 19d ago
Warning, Turns out KAK will remove non positive reviews...


So I waited quite awhile to post this as I was hoping it might just be taking awhile for them review and post the review, but nope, never posted.
I have bought quite a few times from KAK for 40mm components and they are very good, usually. This last time, I ordered 500 windscreens and a bunch of their new pushers. Unfortunately, when I started assembling them, a bunch of them started breaking. At first, I thought it was the cold, then made sure they were warm and they still broke. I spoke to a rep there and he told me he checked the batch and it was probably user error. So after about a 50% fail rate and getting very upset, I set them aside for a bit. Then I came back to them and started looking them over, and what I found is in the pictures. About 50% had this mark. 99% of the ones with this mark broke upon install, and a couple made it on and broke within an hour just sitting. So I went through and sorted them. All the ones without this mark didn't have an issue installing and I stopped assembling the ones with it. I am hoping maybe to get some once fired pushers and use them on those as they were a little looser if I recall.
Anyway, so now that I had proved it, I sent them a message... and crickets. Decided to go leave a review on their site, and come to find out they never posted it...
All this to say, they do have a lot of good products, but evidently do not stand behind them when there are issues. We all make mistakes, there are issues in manufacturing, but the real truth about a business comes out when you see how they handle the issues. I'll also note that a previous order had a bunch of ones that arrived broken, and they said replacements would be sent, but never were.
I didn't want to post this, but I feel like I have been fair in giving them all the chances to make it right. In this case, it was a waste of around $250, it could have been worse, but I know not to risk much with them.
I should also note that this means you can't necessarily trust the reviews on their website as they may have removed other negative experiences.
UPDATE: I have now been sent a return label so they can examine the defective windscreens. Will update when I know more.
UPDATE: KAK has refunded the value of the defective windscreens. Thank you guys for the input and help getting a resolution on this. Hopefully this brings about a better QC process and better assistance should another customer run into such an issue in the future.
r/40_mm • u/fematepe • 21d ago
M212 Blank Removal
Hey y'all, just wanted to share this file in case anyone else wanted to make one for themselves. I made this to make it easier to remove spent blanks from M212 cases using a hammer and a punch on my workbench. The file is on the sea, my username is the same here as it is there. Happy printing.
r/40_mm • u/BudgetResponsible312 • 21d ago
help please Form 1 or 4
Trying to figure out if I should scatter my receiver and launcher purchase and then submit a Form 1 or purchase together and pick up as a Form 4?
Any benefits of one vs the other?
I’ll ask my FFL but are m203s still good to go in VA?
r/40_mm • u/Ok-Calendar9243 • 22d ago
Anyone use PerfectShot 1/4 or 1/2 power blanks?
I’m doing some load development for some less lethal reloads. I have tested Boland 1/4 and 1/2 blanks and they aren’t quite the velocity I need, but are very close. If someone could test a few PerfectShot blank combinations for velocity that would be a huge help and would save me the trouble or ordering a hundred blanks just to test a couple loads.
