Warning

 

Close
Confirm Action

Are you sure you wish to do this?

Cancel Confirm
AR15.COM
Armory Sponsor
5/27/2026 1:54:23 AM EDT
[Last Edit: ABursell][Edited]
I am looking to Form 1 an LMT M203 receiver and 40mm barrel. Hopefully in only one attempt. I have done SBR's and AOW's, but never one of these.

I would like to know what you have successfully used/had approved for this specific model.

For manufacturer, there are options such as LMT, LMT DEFENSE, LEWIS MACHINE & TOOL, Etc. The receiver says LMT DEFENSE on it, so that seems correct?

For model, it says on the receiver GRENADE LAUNCHER, M203. Would I use M203 as the model, or do I need to use GRENADE LAUNCHER, M203? There doesn't seem to be any other logical choices?

Thanks -- appreciated from a first-time DD'er.
5/27/2026 2:20:50 AM EDT
[#1]
LMT DEFENSE

M203
5/27/2026 2:34:25 AM EDT
[#2]
Excellent- thank you!
5/30/2026 12:01:57 AM EDT
[#3]
Looks like this is pertinent to my needs as well. Thank you.
Esstac’s Retarded Social Media Influencer
5/30/2026 12:06:10 AM EDT
[#4]
Exactly as it reads on the receiver. Photos, while not required, usually help.
5/30/2026 5:34:50 PM EDT
[#5]
If you're doing an LMT rail-mounted receiver, they're actually a different model.

They're M2032003
6/8/2026 11:46:08 AM EDT
[#6]
My f1 was done using LMT DEFENSE, UNITED STATES and due to being a rail mount version, I had put model as M-2032003 which is as engraved on my receiver.
6/27/2026 5:18:40 PM EDT
[Last Edit: AK-12][Edited] [#7]
OST

Planning to get a receiver (old school mount for my 6940) and keep a 37mm barrel on it until I get it on a Form 1.
6/30/2026 3:37:14 PM EDT
[#8]
Quote History
Originally Posted By AK-12:
OST

Planning to get a receiver (old school mount for my 6940) and keep a 37mm barrel on it until I get it on a Form 1.
View Quote


I don't know that the barrels are interchangeable.   I beleive them to be a slightly different design to prevent a 40mm barrel on a 37 mm reciever, and vice versa.  So use caution and do some research if that is your plan.
6/30/2026 3:47:26 PM EDT
[#9]
Quote History
Originally Posted By Stan_TheGunNut:


I don't know that the barrels are interchangeable.   I beleive them to be a slightly different design to prevent a 40mm barrel on a 37 mm reciever, and vice versa.  So use caution and do some research if that is your plan.
View Quote


From what I've read it depends on which receiver and barrel you have.

LMT makes a 37mm M203 launcher/barrel that will not accept a 40mm barrel and can ship to your door as it is a "signaling device".

Colt 37mm launchers use an actual M203 receiver that will accept a 40mm barrel, but transfers as a title 1 firearm on a 4473 with the 37mm barrel.

From what I understand, the Colt and McCollum Machine 37mm barrels will fit a standard M203 receiver, so you can transfer the receiver as a title 1 firearm and keep the 37mm barrel on it until you form 1 it into a DD. I have a 12" 37mm Colt barrel.
6/30/2026 7:29:10 PM EDT
[#10]
Quote History
Originally Posted By AK-12:


From what I've read it depends on which receiver and barrel you have.

LMT makes a 37mm M203 launcher/barrel that will not accept a 40mm barrel and can ship to your door as it is a "signaling device".

Colt 37mm launchers use an actual M203 receiver that will accept a 40mm barrel, but transfers as a title 1 firearm on a 4473 with the 37mm barrel.

From what I understand, the Colt and McCollum Machine 37mm barrels will fit a standard M203 receiver, so you can transfer the receiver as a title 1 firearm and keep the 37mm barrel on it until you form 1 it into a DD. I have a 12" 37mm Colt barrel.
View Quote

You are correct. LMT confirmed their barrel won’t work but there are barrels made by other parties that will.

McCollum is one that will.
Esstac’s Retarded Social Media Influencer
7/3/2026 7:21:54 AM EDT
[#11]
Picked up my receiver yesterday, everything went together pretty easily on my 6940. The ninja star fit on the zero dot setting and it did not require any spring washers to fit the QD latch properly.

The 37mm Colt barrel does indeed fit the 40mm LMT receiver.

Sign up to continue the discussion

Create a free account to share your thoughts, follow topics, and connect with the AR15.COM community.

Already a member? Sign In

Armory Sponsor