45 Thompson?

How can you identify the 45 Auto made for the Thompson machine gun from the regular 45 auto pistol round? Vic


It’s my understanding that many cannot be identified once they are out of the box. But, issue #438 of the IAA JOURNAL has a couple of Remington drawings courtesy of Dick Fraser. Issue #436 contains a brief discussion by Vidar Andresen.


If we are talking about the .45 A.C.P. cartridge with loadings special for the Thompson SMG, very few boxes are marked as being exclusively for the TSMG other than blanks. I have several of those in my own box collection. There are two Winchester white boxes with black print, one a 50-round box that says “For Thompson Submachine Guns,” and the other a 42-round box that says “For use in Sub-Machine Guns.” I think both of these boxes were a contract for England. I doubt that the ammunition was any kind of special loading, not only from experience in collecting this round, but also because in the case of the 50 round box, which is lot number 23 of 19 April 1941, I have another 50 round box of the identical lot number, and the same style of print and format, except that it says “For .45 Automatic Colt and Other Automatic Arms.” The 42 round box, by the way, is from Lot 54 dated 30 AUG 1941 (the month is pretty illegible, but I think that it is “AUG” for “August”).

These are about the only ball-round boxes I have seen indicating the ammunition was “special” for submachine guns, and frankly, I don’t believe it was. There would be no reason for it since the Tommy Gun functions flawlessly with any ball ammunition made for the pistols. I can tell you that from personal experience firing them.

Now, if we are talking about the .45 TMG cartridge (Designation taken from factory drawing) made by Remington, you don’t need any box to tell them apart from pistol rounds! The case length is 1.015" - 1.020", much longer than the approximately 0.884" to 0.906" case length of the standard .45 A.C.P. (more popularly called simply .45 AUTO these days) cartridge. This load is found with two bullet shapes - one almost as pointed as the old Highway Master .45 metal-penetrating bullet, and the other is pointed as well, but with a slightly more rounded ogive.

The case length alone will immediately tell you the difference between the .45 TMG, sometimes called the .45 M1923 Thompson, and the normal .45 auto pistol cartridge.

I hope I have expressed this clearly enough, and that is of some interest and assistance.

I have seen a review that identifies the REM-UMC with a nickle primer to be hardened for the Thompson?

Have never heard of special primers for the Thompson. Would be totally unnecessary. On one day alone, we shot 700 rounds of Evansville Chrysler WWII steel-cased ammo thru a Model 1928A1 Thompson without a hitch. Have shot them other times with a variety of commercial and military ammunition as sold or issued for pistols, with no problems what-so-ever.

The gun was designed for the .45 A.C.P. pistol cartridge.

What is your source for the “hardened primer” information? I would like to obtain copies of it and see what it has to say. I have never seen mention of such in any catalog, Thompson manual or other literature, of which I have some in my library, nor on any box label.

The source was a gentleman selling Thompson 45’s so I guess the buyer needs to beware. Vic

Yes, think you’re right. Sounds like the gold old “Gun Show wisdom” at work.

Was he selling the long “.45 TMG” rounds, or the standard .45 Auto cartridges?

Here is a Remington Thompson cartridge compared to a Maxim made 45 ACP. Despite my camera not being that flash for closeups like this you can still see the large difference in case length

I can vouch for the Thompson SMG not requiring any specially designed ammunition to function properly.

A friend of mine owns a Thompson M1A1 and we will shoot it occasionally. I don’t like shooting up all of his ammo, so I feed the weapon with my own reloads that I make for my two 1911 pistols. The reloads are composed of 230 grain lead bullets and use Winchester large pistol primers with about 4 grains of Bullseye.

The above is a target load for the 45 ACP and it functions flawlessly in the Thompson. The guy who owns the Thompson doesn’t like to reload so he buys the cheapest factory made 45 ACP pistol ammo he can find. It works flawlessly too.

Therefore, I also concur with John that the Thompson does not require specially loaded ammunition to function properly.


The only two loads made specifically for the Thompson that I can think of are the lengthened Remington-Thompson rounds shown by craigt above (used in a short-lived Squad Automatic Weapon version of the TSMG, with bipod and drum mag), and the “riot-control” shot loads. The riot control loads used a special 18-round stick magazine that resembles the standard 20-round sticks.

Dittos on the comments re special primers for the TMG. I have fired many thousands of rounds thru both commercial and GI Thompsons, including many handloads, and have never experienced any primer problems. The later GI versions did not even have a firing pin and worked as well as, or better than the commercial guns. Sounds to me like someone who either doesn’t know what he is talking about or does know and has larceny in mind. JMHO

Hey heavyiron - better edit your post before someone does it for you. :) :)


The photo that Craight shows is the version with the slightly more rounded ogive to the bullet. The tip is as pointed as the other variation, but the ascent to the tip does not begin as soon as that on the other bullet variation, whose ogive begins almost at the case mouth.

I made an error of commission and an error of omission in my main posting on this round. I have edited the first error out - this round really never had a bullet similar to the standard FMJ RN bullet of a regular .45 A.C.P. “hardball” round. When I posted that, I had forgotten how pointed both bullet variations are.

I did not mention the headstamp on the long Thompson rounds. Although a factory drawing shows the proposed headstamp as “REM-UMC .45 TMG” there are no known specimens, to my knowledge, of that headstamp. These rounds have a standard “REM-UMC 45 ACP” headstamp, adding to the confusion about them.