Thompson SMG riot cartridges

How common are these?

I usually can find them at gun shows for a few dollars each.Never have found a complete box. Tom from MN.

The cartridges themselves, both with commercial and with military headstamps, I would consider fairly common. The ones with nickel cases (commercial/police) are somewhat scarcer than the military or commercial variety with plain brass cases, and the ones with blue Sabot rather than red seem to be the scarcest.

I would class the boxes shown as quite a bit scarcer than the cartridges, although not absolute rarities. There are several other versions of the box for these rounds, military and commercial.

Regardless of one’s opinion about rarity of these rounds, they are a very interesting and important part of the collection of anyone who collects auto pistol/SMG cartridges.

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Here are two Peters boxes with similar contents but different uses. The top box has the contents of the video and the cartridge on the left The bottom box (which does not mention the Thompson) has the middle and right examples (also is shown disassembled). Notice the lack of case crimps on the brake test example, which are also much lighter in weight.


Pete - thanks for posting that box label. The Brake Reflex Test cartridges are far rarer than the shot rounds. While there are many variations of the Peters shot cartridges, I have only ever found two variations of what are reported to be the Brake Reflex Test rounds. Both rounds are headstamped “PETERS .45 A.C.” but differ in most other details:

Earliest of the 2 BRT rounds: Red Paper Sabot, brass case with no cannelures, nickel domed primer cup with red primer seal. OACW: 151.7 grains (9.82 Grams).

Later version of the 2 BRT rounds: Red Paper Sabot, brass case with two cannelures, upper one smooth and lower one knurled, nickel flat primer cup with no primer seal. OACW 121.9 grains (7.86 grams).

I cannot explain the 30 grain difference in weight between the one with no cannelures and the one with two cannelures. I am loathe to pull them apart, as I had no duplicates of either. For comparison, a shot cartridge of the same description as first round as to primer, primer seal etc., but with the two cannelures, has an overall cartridge weight of 285.6 grains (18.5 grams).

It is interesting that the over-labeled box for the BRT rounds seems to have no mention of their purpose. I was not aware that the BRT rounds were ever used in a conventional firearm. My understanding was that they were for a special fixture, mounted to the undercarriage of an actual automobile, and that when the break was applied in view of a visible warning, it actually fired the yellow-chalk projectile into the ground, living a visible mark that showed the exact distance between sighting of the hazard warning and application of the brake.

I have never seen anything on this fixture, so am not at all sure that description is accurate. When I took a driving test in the Army (actually in the Army Reserve, after my active duty tour), all this was down on a testing machine that was basically a video game. It was all done electronically, even though that was some 58 to 60 years ago.

I failed to mention in my original entry that the commercially headstamp versions of the shot cartridges are much more common than are those headstamp “R A” but perhaps a little scarcer than the Evansville Chrysler military versions.

John Moss

Interesting John.

I’m going to start another thread on Brake test’s as I have another box.

The total weight of the one I showed is 147.8 grains (so pretty close) & otherwise meets the description of your earliest.

I also have one that is of the same description of your 'later" example, however it weighs only 251.4 grains & I can hear the shot when I shake it (so perhaps it’s lost a couple shot?), so it’s obviously not a brake test.

I’ve also heard the story of a fixture but with the addition of a lanyard to fire it.

But to my mind to record the distance between the sighting and the brake being applied and the actual stopping point would need two markers. So I believe / think these were only for stopping distance tests as it could easily function to mark when the brakes were first applied / the gun fired to where the vehicle came to a full stop.

The military M12 shot cartridges contain a similar “for single shot loading only in .45 caliber pistol” warning sheet inside the 20 round boxes.

Had no idea this post would turn into a lot of real cool info. Thanks for all the education.

Pete - I did not word my explanation of the device very well. It confuses even me. I think you are right about the two contacts, and tried to explain that. There likely was a portable sign that the instructors could put out saying something like “Hazard” or “brake” and that the distance from that sign or whatever visual warning was used, to the yellow chalk on the pavement, measured the reflex distance between warning and using the brake.

That is all conjecture on my part, because I have never seen the device or know if it really was used. The chalk tells me that it is logical that it did. Firing a chalk-laden projectile from a pistol would seem to serve no purpose at all.

The elctronic device used in my military driving test essentially worked the same way, but all electronically. The hazard warning came on the screen, in cartoon form but I don’t remember what it was, and you had to hit the brake, which was an actual floor pedal like in a real car, and then the distance between warning and initial use of the brake was measured electronically. No cartridge of any kind was needed.

I think if I have time today, I will weigh all of my M23 style cartridges by Remington/Peters. I weighed only the two that I believe to be Brake Reflex Test rounds, against a known shot round of the same headstamp and primer as the former.

Decided to put this info on this thread, since these are not for the Brake Reflex Test rounds.

I weighed all of my paper-sabot shot rounds as made by Evansville Chrysler, Peters and Remington (also perhaps Peters, but with R A military headstamps).

Evansville Chrysler. All rounds the same characteristics, generally visually varying only in the headstamp font sizes and letter shapes and spacing. All are brass case, and have two cannelures in the case. All are headstamped, in one form or another, “E C 43.”
The numbering of the cartridges is simply to clearly denote the separate rounds. It has no significance otherwise.

  1. 256.4 Grains (16.61 Grams)
  2. 266.3 Grains (17.25 Grams)
  3. 257.8 Grains (16.71 Grams)
  4. 258.5 Grains (16.75 Grams)
  5. 254.9 Grains (16.51 Grams)
  6. 263.7 Grains (17.99 Grams)
  7. 260.0 Grains (16.82 Grams)
  8. 262.5 Grains (17.02 Grams)
  9. 262.0 Grains (16.96 Grams)

Peters commercial loads. All headstamped “PETERS .45 A.C.” All plain-brass cases except as noted. All with two case cannelures, except as noted. They are arranged in the order, one thru eight, that I feel they were made, based on the total of all cartridge characteristics. I could be off here and there.

  1. 293.2 Grains (18.99 Grams) Note: this cartridge has only one case cannelure.
  2. 268.8 Grains (17.42 Grams)
  3. 279.3 Grains (18.10 Grams)
  4. 285.5 Grains (18.51 Grams)
  5. 270.6 Grains (17.54 Grams)
  6. 248.5 Grains (16.10 Grams)
  7. 264.5 Grains (17.15 Grams) Note: Nickel case with red-paper sabot.
  8. 251.5 Grains (16.29 Grams) Note: Nickel case with blue-paper sabot.

Remington military M12 loads. Brass case, sabots as noted. Headstamp of No. 1 is
“R A 42.” The other two are both “R A 43.” All have two case cannelures.

  1. 257.9 Grains (16.71 Grams) Note: Red full-length paper sabot.
  2. 248.6 Grains (16.12 Grams) Note: Silver full-length paper sabot
  3. 230.8 Grains (14.95 Grams) Note: This include for completeness. The red-paper sabot has the visible (what is outside of the case mouth) length and shape of a 230 Grain, FMJ Bullet), so is non-typical, and the lighter shot load is no surprise.

What did I learn from all this? Basically nothing. The total cartridge weights are all over the board in each type. Evansville Chrysler 254.9 Grains to 266.3 Grains, a difference of almost 12 Grains. PETERS 248.5 Grains to 293.2 Grains (285.5 Grains if we eliminate the first round listed, which is different in that it has only one case cannelure, and I would judge it to be the first of the PETERS types judging from cartridge characteristics.) Even with the lesser of the heavier rounds, that is a 40 Grain spread even eliminating the nickel-case versions. R.A. Hard to make a judgment about the weight spreads since all three rounds are variations from one another.

It is, without documentation, hard to judge if these weights differences were of design, or simply very loose manufacturing specifications. I cannot make that call, so these figures can only be offered here for whatever interest they are to anyone collecting these types.

All weight measurements taken on a calibrated, RCBS Digital Scale that allows instant conversion from Grains to Grams.

John Moss

I found no documentation regarding the tolerances allowed for shot pellets used in the M12 cartridge. But you are not dealing with a single bullet, but a cluster of pellets, each pellet with its own weight tolerance. As a result, the weight of the shot load in the cartridge varies more than a conventional bullet.
IMHO the consistency among the Evansville cartridges is very good, considering they are shot cartridges.

Peelen - in comparison, I agree that the overall cartridge weight spread of the Evansville Chrysler rounds isn’t all that bad. This is not surprising. This company’s manufacture of ammunition during WWII is pretty much a miracle story. They had no prior experience in this area of manufacture, yet were producing very soon after setting up, with ammunition not only in brass cases, but also in steel. In 1957 and 1958, we were still seeing EC .45 ball ammunition in use in the Army. Their production level was so high, that even with the war expected to go on as late as 1947 or thereabouts, they shut down .45 production in late 1944 because they were producing it faster than the military could use it up. Their quality level was very high throughout production.

I guess my surprise at the spread was that I have little knowledge of shotgun ammunition. Despite being a shooter and collector most of my adult life, until I got into Cowboy Action Shooting in my late 50s, I had never owned a sporting shotgun and had no experience in shooting shotguns for any purpose. I did not have a pressing need to know at the store I worked at, because we had two highly knowledgeable, active “shotgun guys” to take care of that department.

Thanks for your evaluation. I have a huge respect for your opinion.

John Moss

I will try to post some pictures of boxes for these .45 shot cartridges that I have in my own collection and already have photos of. If I do this successfully, there will be a little duplication with previous pictures, as some are “group pictures.”

My God, it worked! My first go at posting multiple pictures.

John Moss

John Moss


Really GREAT boxes John, THANKS. That one with the patent date is just super.

To add to the mix, and although not exactly a shot loading by name, or noted specifically for the Thompson, it is a “riot” load, and it is a multiple projectile loading but unfortunately it is just the top of a box.

Here are pictures of the M15 Shot and riot ctgs.




Pete - Thanks. . Great!!! It is a treasure whether just the top or not. If it is like mine, than the top is all that is germane, since the Riot Load label on my box is an overlabel on a ball box. I will try for a picture of it, again from an H.P. White Lab Card. It shows all the other labels from the box, including the top one that was covered by the Riot Load label.

My early T-23 box label is just those parts of the box that were different from one another, on an H.P. White Laboratory file card. I am still glad I have it. I got it at a Mundalein Show, the older Chicago ICS, years ago, along with a few other good labels, like an original 1906 .45 label, also on White Lab cards. You can see that some of the other labels were for the Riot Load as well, also over labels like the top label one.

Thanks for posting it.

john M.

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Yes John it is an overlabel on another box, undoubtedly the same box as you show & it can be seen along the left side & bottom edge

O.K. this time it worked. For some reason, my computer has decided it takes one more step to enter a picture.

Top Row, left to right: PETERS shot cartridge with single cannelure; PETERS shot cartridge with two cannelures; PETERS shot cartridge with nickel case & red sabot; PETERS shot cartridge with nickel case & blue sabot.

Bottom Row, left to right: Remington M15 type shot round with commercial REM-UMC headstamp; Remington relatively current shot cartridge with R-P headstamp including the word “SHOT;” CCI Aluminum-case shot load with short mock-bullet profile; CCI shot load with longer OAL of the mock bullet.

I will try posting a second and third picture as well.

John Moss


Edited to delete duplicate picture.

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