A couple questions pertaining to the M203 40mm


Dan Forrester
January 21, 2008, 05:41 AM
I know quite a few of you guys are current or former military; so thought you might be able to help me out with a few questions.

What parts commonly break on these guns? Iím looking to build up a basic spare parts kit. Iíve heard the leaf sight is easily bent. Firing pins are all over the place, but Iíve never heard of them breaking.

Is there an armorers manual for these launchers. I see the basic intro to their operation and use, but Iím looking for a manual which goes into detail on the complete disassembly, replacing o f broken parts, looking of abnormal wear, ect.

Any help would be greatly appreciated.

Thanks, Dan

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January 21, 2008, 08:34 AM
Can't help you myself, but here's the field manual (http://www.globalsecurity.org/military/library/policy/army/fm/3-22-31/index.html).

January 21, 2008, 08:38 AM
You probably already know this, but don't store it loaded. :)

AD with a 40mm (even a chalk round) isn't fun for anyone involved.

Big Daddy K
January 21, 2008, 09:04 AM
Never had one break. Pretty simple design.

January 21, 2008, 09:34 AM
AD = very bad.
My father tells a story about a co-pilot (Hueys) who became enamoured of one back ~ 71-72. He shot himself in the thigh in mid-flight.

January 21, 2008, 09:39 AM
I never had it break on me. Carried one for about 6 years (had to argue with a LT. once to keep it as an E-6) The gradient sight isn't very good, I always used the leaf sight.

January 21, 2008, 10:34 AM
About what's the barrel life on those? From what I've read, the Russian GP-30's barrel only lasts for 400 shots! The M203 has to last longer than that!

January 21, 2008, 11:04 AM
When I was with the 2nd Mardiv the only thing I remember breaking on one was the lock on the slide action.

January 21, 2008, 12:08 PM
I can see maybe the plastic grip cracking, but never seen it happen myself, i think that only really happened with the early ones when you'd bring them into a warm building after being out in the cold. I did see a guy in my unit touch off a training round with the sling in front of the muzzel, tore the sling off the rifle. while the sling was leaving the rifle it took a good chunk out of the guy's hand. When everything was said and done, you had a bright orange rifle and soldier with a bleeding hand.

January 21, 2008, 12:32 PM
Wait a minute... these things are LEGAL???

January 21, 2008, 12:41 PM
I've been working on those pigs for over 30 years; very little actually breaks. Lots of stuff gets bent, though, including the barrel. Barrel life? I actually can't say; I never had to replace one because it was shot out; they usually get dented first.

As far as a TM, look here: http://www.gunbroker.com/Auction/ViewItem.asp?Item=89777937

January 21, 2008, 03:09 PM
Wait a minute... these things are LEGAL???

Much like any other NFA weapon (machineguns, short barreled rifles/shotguns, non-sporting firearms over .50 cal, etc), grenade launchers are perfectly legal for anyone that can jump through the hoops, pay the $200 tax, and afford the gun.

January 21, 2008, 03:21 PM
Much like any other NFA weapon (machineguns, short barreled rifles/shotguns, non-sporting firearms over .50 cal, etc), grenade launchers are perfectly legal for anyone that can jump through the hoops, pay the $200 tax, and afford the gun.

That's true as far as it goes. Under Federal law they are legal, after you pay the tax. Under state law though it depends on the state. A 40mm GL is a "Destructive Device" and not all states allow their residents to own such a thing, even though it's legal under Federal law.

Check your state laws first.

January 21, 2008, 03:33 PM
When I was in the Corps, a guy once flashed the line at the range with his 203. He got beat up pretty badly.

I never heard of a 203 breaking, however.

January 21, 2008, 03:44 PM
Technically, the M203 is a large bore destructive device, which are legal in most states. However, if you want actual grenades for it, each and every individual grenade must be registered as an explosive destructive device, which more states forbid. If you're in one of those states, you're stuck with reduced-lethality rounds and practice chalk rounds only.

A new in box M203 goes for about $2000 plus tax and transfer fee, I believe. Don't know what actual grenades go for, but they're extremely rare, and I wouldn't be surprised if each one costs more than the launcher.

January 21, 2008, 04:04 PM
I am not even going to ask why you want to know this.

The only M203 issues I have ever seen come up is the in-housing trigger safety can sometimes break; and the sliding foregrip can stick or crack as it is just plastic. You have to understand that these things are practically unbreakable and the ones I have seen problems with were only 2 in the 100s I have personally handled and they were probably from the 1970s era of manufacturing (which most are anyway).

There you go!


January 21, 2008, 05:30 PM
I am a former armorer. Watch for the firing pin seat to get loose. Once loose firing will strip the threads and it must then be replaced. Loctite is your friend.

The barrel extention will become loose on the barrel. It is the long guide that rides in a groove above the barrel. Remove the barrel and turn it over. If you can wiggle the extension stake it in place.

January 21, 2008, 05:30 PM
Oh, yeah, we can't have Destructive devices in Florida, so I guess I got my hopes up for nothing.

January 21, 2008, 05:53 PM
I don't think there is any distinction between explosive DD's and non-explosive ones. Just when the chief LEO reads what you are getting, does anyone know a chief LEO who would sign off on a 40mm?

January 21, 2008, 08:56 PM
Federal law doesn't distinguish between explosive and large bore DDs, but some states do. PA outlaws explosive ones, but not large bore. Several other states are like that. Colorado requires a state permit for explosive DDs. Georgia and Oregon prohibit incendiary DDs but not regular explosive ones. Nebraska is the same as PA. TN says explosive DDs may only be used for "lawful industrial or commercial enterprise," so that's as good as a ban.

Elm Creek Smith
January 21, 2008, 09:16 PM
Anyone have an idea how much an M79 would go for? I miss mine.


Wes Janson
January 21, 2008, 10:28 PM
Oh, yeah, we can't have Destructive devices in Florida, so I guess I got my hopes up for nothing.

Says who? AFAIK, DDs are completely legal in FL. Hell, we've got the second-most number of SOTs here, IIRC.

Dunno precisely, but I believe M79s are running around $6-8k.

Big Daddy K
January 21, 2008, 11:30 PM
Dummy/chalk or whatever is in em would be fun to shoot. Dont really want an acual HE type round. Oh who am I kidding? I do too.

Dan Forrester
January 22, 2008, 12:53 AM
Wow! Quite a few responses to this post. I was expecting maybe one or two. It seems as if quite a few of you have some real experience with these things. Iím enjoying these stories some of you guys have; especially the one about the sling getting in the way. Keep them coming. I have absolutely no experience with these things whatsoever. The first time I actually handled one was when mine arrived at my dealer. Itís much easier (and safer) for me to learn form you guys who are experienced with these things, than for me to learn it the hard way.

Ok so I bid on that armorerís manual (TM 9-1010-221-24&P) nicholst55 pointed out. That should have an exploded parts diagram so I can better identify these parts a little better. But so far I have:

- Slide action lock.
- Plastic grip and barrel, which are all one piece anyway.
- Safety

What about the firing pin and extractor? No problems with these? The M203 firing pin seems to be the most common spare part out there. I figured that was because these were always breaking, but after reading this it sounds like these things are damn near indestructible.

Jcord: Thanks, I will check those two things as soon as I get it.

Who makes most of the M203 in the US Militaryís inventory? Colt, LMT, RM Equipment, or someone else.

Elm creek smith: It shouldnít be to hard to build an M79 from a new receiver and surplus parts for under $3,000. Randy Shivak (google him) makes brand new milspec M79 receivers for $1,700. Add a new surplus barrel on for $800 and that leaves you with $500 to spend on the internal parts which you can pick up form Numrich Gun Parts. As ďWes JansonĒ said however, the original, un-cut military surplus launchers go for the $6-8,000 range.

Signoffs donít matter these days with the trust. If you can find a transferable claymore mine you just buy it on your trust. Thereís no need for a sign off. Once your form 4 for the claymore gets to the ATF it should be no different than any other NFA item. However in my case my CLEO signed me off. He talked with me for a couple minutes just about random stuff, looked at the form 4 said those M203s look great when mounted, and signed. We talked for another 10-15 minutes about local county issues and before leaving I donated $100 to his re-election campaign.

Yes large bore DD are legal in Florida. Iím in Florida, as is my dealer, and the CLEO who signed me off is also. Large bore DD as well as explosive DD are perfectly legal in most states except for the usual: CA, IL, MD, NJ. I think they are legal in NY however. You should double check this however as it might have changed.

HE grenades are difficult to find, but they are out there, and available to civilians. Iíve heard of two places which will transfer them to civilians on a form 4. It would seem you could register and empty case as a DD, then load it with an HE projectile. After firing the round you ďrepairĒ your DD by loading up a fresh HE round. If you did this on an ATF form 1 you would be the manufacturer so could make ďrepairsĒ. I still need to look into this but havenít had the time.

Thanks for all of your responses and good stories. keep them comeing!


January 22, 2008, 01:26 AM
Where's the love for the M79?

Dan Forrester
January 22, 2008, 08:44 PM
I would love an M79. The problem is that they havenít been made in 30 or so years. M203 are in current production, and the company who has the contract with the military (LMT) doesnít mind selling them to civilians.

I have another question for you guys: Before storage should I dry fire the M203 or leave the hammer cocked? What about dry firing in general? Will it hurt them?

Thanks, Dan

February 5, 2008, 10:57 AM
The 203 can be dry fired without a problem, but if you want a simple solution, buy a 38/357 snap cap and put it in one of your M-212 casings... GROG

Elm Creek Smith
March 28, 2009, 02:27 AM
Anyone remember the "shotgun" rounds for the 40mm? IIRC, there was a buckshot version and a flechette version.


March 28, 2009, 03:38 AM
The plastic grip on mine cracked, you just turn in the barrel (which is connected to the grip) and get a new barrel assembly.

March 28, 2009, 05:45 AM
I had a M79 off and on in Vietnam. Ammo was heavy. Carried HE, gas, and buckshot rounds. The ammo vest sucked so usually had a couple of gas mask bags. Hard to carry a lot of ammo. Mostly HE. Can shoot flares in them. Are good for putting a strobe light in to signal gunships so they know where you are without flashing all over the place. Are dangerous in bamboo thickets. Very good for shooting at noises in the dark without giving your position away with muzzle flash. Once had a four shot clip fed version. It had four rounds in a stripper clip that loaded from right to left in a fixed frame model. A spring extended on the left side that would push the clip to the right as you fired.

March 28, 2009, 07:08 AM
Once they were working on a four round pump version of the M-79 fed from an under barrel tube like a shotgun. They decided that it was too heavy for use.

March 28, 2009, 07:20 AM
i have used both the colt as well as the lmt, have not had a problem with either on of them. i personally prefer the lmt, it seems better built. there is an fm for the 203 like everything else in the army and that should be able to square you away. i reccomend that you go with the 37mm though, it is really hard to get any kind if ammo for the 40mm, the 37mm is easier to come by.

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