Rather than search for a Title 1 cup, I'm interested in making my own.

I have a copy of the machining prints for an M2 mortar cup. I have access to a retired machinist who is quite knowledgeable and interested in the project.

That takes care of that. Barrel can be made or buy an already existing one. Other parts to be searched for and assembled.

Most important part:

I have a trust with stamps already and would like to e-file paperwork on the M2 before the 41P goes into effect this summer.

Does anyone have any experience doing so? What barrel length, OAL, etc did you use?

TIA.

Hey Mr. ATF man

OP has indicated he knows how to play by NFA rules, and what he's asking is legal.... so are you saying you don't know the NFA rules, and don't know how to listen and learn?


OP:  While I do have my own form 1 DD projects, I don't have a mortar or know much about them. Do a goole search for the mortar you wish to duplicate.  Specs for US made stuff should be readily available.  Better yet, find a copy of the TM for the mortar you wish to build... the answers will be found there.

Head over to the ReardenArmament.com forums for all the info that you need to build an m2 mortar from scratch. It is a tremendous undertaking and will likely take years. Start watching eBay for parts and accessories now.

LOL. I'm asking what OAL, barrel length etc to fill out on a F1 for something that lots of folks are interested in. On ARF's DD forum where other folks have done it and posted build threads on.

Does your Daddy know you're talking to grown ups on the Internet?

Perfecto. I'm here and on Grog's, this is what I was looking for. Thanks man.

ETA: I'm gonna PM a follow up question.

I have a newly made barrel and cup.  The barrel length I used on my form 1 was 25.5 inches and overall length of 28.625 inches.

Thank you!!!! I have a newly made cup as well. Any reccomendation on sourcing a newly made barrel?

Don't forget the little things like muzzle covers, sights, crates, EE-8B field phone, aiming stakes, whiz wheel, etc.

Wing, the shot of your boy with your M2 sealed the deal for me. I am also getting some other stuff ahead of 41p to make sure I can pass something along to the next generation.

Any other Form 1 specifics on an M2 are very helpful. Is there a source for brand new barrels?

No good source for barrels yet. Working on that though.







I have my own mortar team and will have a little grenadier showing up in October.

You do know that 41f won't prevent you from filing Form 1s & 4s, right?  Slightly more of a pain in the ass for trusts, but still just a paperwork drill.  Much easier for individuals.

Yup. It's also a bit of a mental goal to have most of my NFA stuff done by then so I can focus on other things. Plus who the hell knows what's gonna happen, one side being Hillary and the other being Nolo's lawsuits.

There's a giu on the 1919a4 forum selling machine blueprints for the M-2 cup for iirc $25 or so shopped

We're in the same boat. Although I'm willing to jump through post 41F hoops, it's more like a mental stepping stone

from my notes the barrel length is 25.75" long, with tube and ball overall length is 29".  OD can be 2.75" with the ID of 2.392"-2.410"   I'll double check what I can later

Here are the basic dimensions for a U.S. 60mm mortar barrel as measured from a M2 and supplied on line at G503.com forums

Outside diameter..................................................2.720"

Inside diameter....................................................2.394"

Diameter of threads..............................................2.835"

Pitch diameter of threads.......................................2.783"

Thread pitch..........................................................12 TPI

Overall length of barrel..........................................25 5/8"

Length of barrel protruding from base cup/receiver when screwed together...................23 15/16"

Length of threaded portion from bottom end of barrel...............................................1.750"

Thread size is not an English standard, if you have a Mil spec cup you will have to match it by using it as a go/no go gauge


I made up a few prototypes and after 5 iterations ended up 3d printing an adapter for threaded aluminum beer bottles to use 60mm mortar fins.

Is it possible to make practice rounds that are not NFA or does any round have enough propellant to be considered a DD?

If the round has no explosive charge, it is just solid like the M69 practice round or contains no explosive then the round its self is not an NFA item.  Well less than 4 oz explosive in the projectile.

The device they are launched out of would be the DD.  If you build a spec 60mm mortar and it utilizes the firing pin to initiate the launch charge it is a DD.  I have been told, but not seen a determination letter, that if you use a firing pin and loaded shells of lift charge then the device is a DD. One way people get around it is they use black powder in the base of the cup as a lift charge and use a fuse to initiate.  They often have the bore undersized to help aid in the argument that it can not be readily converted to a DD.

I figured I better do this too. Just submitted my form!

Unfortunately I put my trust name for the manufacturer instead of "FMI".

This interests me....

So a bit off topic, where does one get the associated bits like the tripod, base, sights etc?

I can handle the cup and maybe the barrel.

Watch for them to come up on eBay or gunbroker or make your own.

The barrel is actually pretty difficult to do correctly, even for full time DD manufacturers.

M-2 barrel is pretty simple I thought...it's once you get into the barrels with the outside threads and/or cooling fins that it gets complicated

The hard part with the barrel is it is not a common standard dimension on the inner diameter.   It must be line bored,  honed or someway opened up to spec.  The outer diameter is not common either but turning the outer diameter is not difficult.

Per the TM, the 60mm barrel should  be:
60-mm mortars --------------2.392 to 2.410 in.

Anyone know of what type of steel should be used?

Also what wall thickness?

Does anybody know how much pressure 60mm projectiles make?