Help with odd 32 ACP

This cartridge came to me marked 32 S&W Auto Experimental but I think it may be a Colt experimental. Does anyone have any information on this?
It is a rimless case not a semi-rimmed. with metal capped lead bullet.
All measurements match the 32 experimental Colt Automatic Pistol on page 139 “Cartridges” volume ! by Datig. That ends by saying “No definite data available”.
Any information or thoughts on my identification would be appreciated.
Thanks , Bob



Here is an older thread on the subject:

I would also be interested to hear more on this one and perhaps Mr. John Moss has some thoughts to share being he’s into the auto pistol end of things…


This is a complicated study, to say the least, as I don’t feel it can be understood with mentioning what appears to be (not my wording, as the documentation for these rounds is sparse in the extreme) a series of at least 4, and possibly as many as 7 different rounds.

One of them is a cartridge named by UMC as “7 m/m Browning.” I have never seen a single cartridge that could be attributed to this entry in the UMC Log. That does NOT mean they don’t exist. I have no specifications on the cartridge, other than the sparse information contained in the UMC Cartridge Log. The following entry is there:

July 1908 - Commenced making samples (up?) per Browning letter dated June 14, 1908.
Aug. 7, 1908 - Sent sample of loaded catridges, primed shells and bullets to Mr. Browning. Shell and cartridges same length as 25 caliber Browning, cartridge not crimped. (a few short words, “as” and “25” are difficult to read but this was the most logical interpretation to me).

There is nothing else on this early experimental cartridge that I have found, anywhere.

Still earlier in the log is a cartridge named by UMC as .30 Cal. Browning. There is only a single Entry, but it matches well to a known cartridge"

Mar. 1904 - Commenced making experimental lot for Browning. Bullet 64 grains. Diam. 288, mix1-6A. plain not grooved.

The above entry seems to match a cartridge in my collection which has a half-mantel, also called “capped” or “Metal-capped” bullet that has a jacket measuring 0.2885" (7.33 mm) at the base of the jacket, above the case mouth. However, the true maximum bullet diameter is greater, as there is a very thin amount of lead showing below the jacket, above the case mouth, that measures 0.2945" (7.47 mm) the best that I can measure it. It has a smooth case cannelure that likely is positioned to prevent bullet setback, which would make the entire bullet about 0.471" (12 mm) in length. Primer is copper, with “U” marking. Headstamp is U.M.C. .32 A.C.P. It is a true rimless cartridge, so is not simply a 7.65 (.32 A.C.P.) Browning/Colt cartridge. This may be the cartridge sometimes called .30 Smith and Wesson, perhaps because of the Half-mantel (capped) jacket with lead lower-half, relative typical of the .35 Smith and Wesson cartridge that came much later.

There is a third cartridge that has a case and overall length almost identical to the one above, except that is has the capped bullet with slots and locking flanges to hold the jacket to the core, another feature prominent on the later Smith and Wesson .35 caliber round. This round is headstamped REM-UMC .32 A P (note the absence of the “C” for Colt), and has a nickel-cup primer with “U” marking.

The next cartridge I am looking at looks like an over-sized .25 A.C.P. (6.35 mm Browning cartridge. It is unheadstamped, has a case cannelure, and a copper-cup “U” primer. 0.2745" (6.99 mm) diameter bullet measured at the case mouth. It has a CN FMJ.
This may be the .28 Caliber Smith & Wesson round, using the popular name for it. This cartridge is likely meant to be rimless, although it has a slightly rebated rim - 0.2995" (7.61 mm) with base at 0.303" (7.70 mm).

The final cartridge has a rim of 0.296" (7.53 mm) and a base 0.2985" (7.58 mm). The bullet measures 0.2580" (6.55 mm) at the case mouth, and like all the others, is a nickel or zinc-plated FMJ RN jacket on a lead core, (all non-magnetic). The bullet is of the capped lead-core type with the slots and leading (from the core) locking flanges so typical of Smith and Wesson. I do not have any opinion about the correct designation for this round, but is is usually called the .26 Smith & Wesson. This round, by the way, had a copper “U” primer, and no headstamp.

More information can be found in Datig’s books, although scant in my opinion, and in Erlmeier-Brandt Vol II Hanbuch der Pistolen- und Revolver- Patronen, published 1980.

I doubt this does more than compound confusion on these rounds, but that is the nature of the beast with these four cartridges in my collection, plus the fifth, from the UMC Log (7mm Browning Auto) which I have never seen.

There are also a couple of case lengths of experimental .38 Auto rounds pegged with the Smith & Wesson appellation, but I have never seen either, even though specimens exist in better collections, and know little about them.

The biggest feature tying these rounds to S&W are the capped bullets. If they were not there, because of the timing of most of them, and the few mentions in the UMC Log, I would think they had nothing to do with S&W. Because of the bullet designs, however, I am not willing to make that statement.

Edited for typos and to add the term “metal-capped” only.
Edited a second time to use the correct word from the UMC Log, that I found illegible. A member with far more knowledge of the tech end of cartridges than I graciously sent me his interpretation, which I found to be unquestionably correct. I thank him.

John Moss


I had figured if there was someone with the scoop on this it would be you! The wealth of info you provided is very welcomed.

The UMC log reference I found interesting and perhaps is related to the more common “.32 S&W Auto” that is often seen on the collector market is:

June 13 1911 S&W order for 5M cartridges (#9558C) like last metal point only perfectly headless and not crimped)

I have no idea if this would relate to the subject cartridge but would think it might have been an early step towards the rather redundant .35 S&W Auto.

Thanks for any thoughts on that.


Dave, thank you for pointing that out. It is an important point that I agree with. I know the UMC log pretty well, but just had a total mind blank about that particular entry. It is good that wiser folks pick up on these things. Yours was the second excellent correction/addition to my comments.

John Moss

John and Dave
Thanks for the very interesting information.
There are a lot of people on this forum with a great deal of knowledge who are willing to share.

Isn’t this the so-called M-1924 model?

Pete - I not positive what you are referring to, but I assume it is the last couple of entries on the .32 S&W Automatic Pistol, a very rare gun - they made, I believe, only about 950 of them - and its cartridge. I have never heard the “Model 1924” designation, but then I never collected .25 and .32 caliber auto pistols, and that designation is perfectly accurate since production of that model was from 1924 to 1936.

Despite the UMC Log calling the cartridge #9558C the “.32” S&W Auto, my feeling is that it was more like a prototype for the .35 Smith and Wesson Pistol. The cartridges, as is noted in the Log, were made in mid-1911. That was about 13 years prior to the manufacture of the first S&W .32 automatic, which in production was for the normal .32 A.C.P. cartridge, now called simply .32 Auto. The timing of the UMC cartridge in question seems, logically, much more likely to be part of the experiments for the cartridge called “.35 Smith & Wesson” by S&W. The .35 S&W pistol began production in 1913, and was phased out in 1921. By serial number, it appears they made 8,250 of this “Model 1913” pistol.

Just my thoughts on the matter.

John Moss

Hi John
I was referring to the round in question on this thread, & have this cataloged as a .32 S&W Auto Model 1924.
Referenced in Datig Vol 1 pg 139 top, EB (vol 1) # 333, Suydam pg 264 and White & Munhall Pistol & Revolver Cartridges, 2nd printing pg. 39.

Pete - o.k., as I suggested might be the case, I misinterpreted the gist of your question. However, the round that started the thread was made by U.M.C. and so headstamped, so was made before 1912 and therefore, I don’t think it could be cataloged correctly as a Model 1924 cartridge. I suspect that the cartridge headstamp REM-UMC .32 A P, with a nickel-cup “U” primer, which is think is basically a rimless, not a semi-rimmed, round (head/rim 0.849" and base 0.847") is likely the prototype round for the S&W .32 Auto Pistol made in 1924, although the production pistols were for the standard .32 A.C.P. cartridge.

The REM-UMC round has the FMJ RN capped bullet with lead locking flanges holding to metal cap to the the lead core, pretty typical of Smith and Wesson. I only have four of these experimental case types - there may be more - but of the ones I have it is, in my mind, the only likely candidate to have anything to do with the “1924” pistol, as the others of my four are all UMC production, making them awfully early to be related to the pistol or to have a 1924 designation of its own.

John Moss

I have been delving even deeper into the subject of the two rounds that are most similar to the standard .32 ACP, that I have in my own collection, which includes the cartridge this thread began with. This IS, by measurements taken from my own round, the cartridge shown on the reproduction of the page from Fred Datig’s books on cartridges shown above, with the title .32 Experimental Colt Automatic Pistol.

This cartridge is identified in the UMC Cartridge History Log (the log mentioned throughout this thread) under the section titled “.32 Automatic Colt, M.C. & S.P.” There are two entries for two similar cartridges, one with the semi-rim of the standard .32 A.C.P. cartridge, and one rimless. The Datig page is on the rimless and I therefore assume the cartridge shown at the top of this thread is the rimless version. No separate measurement is given for that precise cartridge, but I have never seen one of the semi-rimmed versions, of which they made only 1,000 rounds on June 21, 1910, for Smith & Wesson.

The rimless round, which is given no designation other than “.32 Automatic Colt” by UMC, is listed as follows:

June 18, 1911 - S & W order for 5M cartridges (#9558 G), (or possibly S - it is an oddly shaped letter - my comment, not in the log) like last metal point only perfectly headless and not crimped.

The cartridge first shown on this thread fits that description. It appears that this round had no official designation to separate it from .32 A.C.P.

The two cartridges with no headstamp and only a “U” copper primer could not be found by me in the Cartridge Log. I checked the log for the approximate calibers of the two rounds, .26 and .28 respectively. The log is long and my time right now is short. It is not impossible, given that American cartridge names do not always accurately reflect the true diameter of the bullets in the cartridge, that they could appear under some other caliber designation.

John Moss

John and Pete,

Thank you for the additional discussion and information. Very interesting topic for sure.

To add some additional visual reference to this current thread, here is an image from the thread I referenced above with an example of the topic cartridge in the middle between a regular .32 ACP on the left and a .35 S&W on the right:

From L-R:

REM-UMC 32 ACP weighing 116.0 gr.with a 70.3 gr. bullet .312” dia., ND = .335", HD = .334", RD = .355", CL = .679", “U” copper primer.
U.M.C. .32 A.C.P. weighing 113.7 gr. (the subject of this thread and I didn’t pull the bullet…) ND = .335", HD = .336", RD = .336", CL = .679", “U” copper primer.
REM-UMC 35 S&W weighing 122.0 gr. with a 75.6 gr. bullet…317” dia., ND = .346", HD = .349", RD = .347", CL = .674", “U” nickel primer.

Less than perfect headstamp pics of these can be found in the earlier thread referenced.


You can see the relationship of the center cartridge above to the, the one I discussed in my last entry above, to the .35 S&W by a feature that I completely forgot to mention, and that is the unusually-wide extractor groove and extractor-groove bevel.

Thanks for posting that picture. My whole photo setup is down right now due to new software that I cannot seem to use correctly.

I like this little group of cartridges, and originally thought they were a “series.” That included the so-called .26 and .28 caliber rounds. Now, I think the only series are the two rounds relating to development of the .35 S&W Cartridge (the round primarily featured on this thread), and the later cartridge, the REM-UMC round with nickel-cup “U” primer that almost certainly relates to the Smith and Wesson .32 Auto pistol, even though that pistol in its finished form used the standard .32 Browning/Colt cartridge.

I am not saying that the smaller caliber versions could not have had something to do with the Smith and Wesson company, by the way, simply that I think they may have been for experiments that went no where, regardless of who they were for. I could be totally wrong on that, of course. I need to find time to go thru the whole UMC Log to see if I can find those rounds, neither of which are headstamped, but have the copper-cup “U” primer. My first efforts indicated they were not in the log, but to find anything, you must have some idea of the nomenclature UMC assigned to a specific cartridge case type.

I want to thank cztrouba for starting this thread. I thought I had a good handle on these four cartridges, but clearly, I did not. As I originally stated, they are a somewhat confusing little group of rounds, but I discovered some things I had not find before due the cztrouba initiating this thread.

John Moss

Thanks, John Dave & Pete
Here are measurements for my cartridge
bullet metal cap .290
bullet lead band .309
neck .334
head .336
rim .336
case length .680
OAL .973
weight 112.4 gr

To all contributors to this post!!
I would not dare to get involved in this discussion,simply I do not know
enough of the subject,However I am in possession of CHARLES SUYDAMS
book US CARTRIDGES AND THEIR HANDGUNS,on page 264 there is a
write up about this cartridge and a pistol for those of you that desire another
view take a peek as everybody knows Suydam is one of the out standing
experts in the field of collecting