What are these-Autopistol Cartridges


I have recently acquired several cartridges from a single source here in Utah but have been unable to positively identify them. I don’t have a set of calipers so I have used side by side comparisons in the photos.

This is my first photo post so here goes.

Unknown1 appears to be close to a .25 acp (seems a hair larger) but has no headstamp. Only a U on the primer. Bullet appears to be lead.

It is shown compared to a USCCo .25 ACP with jacketed bullet.

The next photo shows the headstamps.

Unknown2 is bigger than the .25acp but slightly smaller than the .32acp. It also has no headstamp, only a U on the primer and a jacketed bullet.
The next photo shows it compared between the USCCo .25acp and a WRACo .32acp.

The following photo shows the headstamp comparison

This next photo shows a .32 ACP I have not seen before. The Headstamp is U.M.C .32 A.C.P with a U on the primer. No visible cannelure on the case and a jacketed bullet.

See headstamp photo:

This cartridge is also at extreme left in the next photo:
From Left: UMC .32acp, USCCo .25acp, U unknown1, U Unknown2, WRACo .32acp

Any ideas what I have here?

Pat S.
Utah Cartridge Collector


I would say the unknown lead bullet round is a .25 ACP, Theres not much in the way of alternatives so I can’t see it can be anything else.
Rim seated small auto rounds don’t require the dimensional exactitude of the larger front seating cartridges. It could just be that your comparison round was made a little on the skinny side. Some of the fired cases from these little guns do show signs of expansion indicating loose chamber tolerances in manufacture. Its probably how they achieved reliable feeding in these low budget guns.
But as always, that just my guess and I’m happy to be corrected.

The unknown 2 is a bit more problematic, it is front seating and appears to be about .30 cal


Pat, the unheadstamped .25 ACP appears to be just that (your no.1) , but without dimensions it’s very hard to be certain. Mine has a jacketed bullet & prototype U.M.C.Co. ammo is sometimes found unheadstamped, but with just the primer stamped U.
The other might be the .26 or the .28 Browning expmtl. but without dims. ???



Borrowed a set of calipers and here are some dimensions.

Rim Dia .297 in
Neck Dia .277 in
Case length .606 in
Can’t really get a good bullet dia as lead is soft and has some dings

Rim Dia .298 in
Neck .300 in
Case length .610 in
Bullet dia .280

If Unknown1 is a prototype .25ACP from UMC what would be the approximate date of production?


Pat S.


your No 1 fits in the 6.35 Browning / 25 ACP dims.

As to when UMC prototyped it I’m not sure but the pistol is ca. 1906 from FN & ca. 1908 from Colt as the 25 ACP according to Brandt.
However the UMC book lists: June 1904 as “commenced making experimental lot”.
In Jan. 1907 “Commenced making these for “export market” in metal cased bullet”.
So between June 1904 and Dec. 1906 it could have been manufactured.

Your No 2 doesn’t quite fit the .28 Browning expmtl. as Brandt lists case length as .614-.615 however as an experimental, it could be “close enough for government work”?

Perhaps John Moss will know ?


Thanks for the info. Both Unknown1 and 2 came from the same fellow out here and he had 6 of the Unknown2s all in roughly the same shape I may try to drop by and see if we can measure those when he gets back.


Pete et al. Well, I purposely was avoiding this thread, as these rounds confuse the h–l out of me. But, I will give it a try.

Firstly, I believe it is an error to intimate that UMC auto pistol cartridges with no headstamp and a “U” primer are “prototypes.” In some calibers, they simply exist today in far greater quantity then they would if they WERE prototypes. That is not to say that none of them could be, but it would require a lot of provenance to prove it one way or another. In the case of 7.63 Mauser, I have a box with cartridges packed on C96 stripper clips, all rounds having no headstamp and a “U” primer. It is obviously a serial-production box with serially-produced cartridges.

Now, the UMC .25 auto shown on this thread is described as haveing a “bullet appearing to be lead.” I have never seen a “U” primer, unheadstamped .25 with a lead bullet, although that of itself means absolutely nothing. Cartridges I have not seen in my own field, but are known to exist, are legion. It is the doubt registered in the description that becomes a confusion. Regardless, I agree with Pete that the dimensions given are indicative of a standard .25 Auto Pistol cartridge.

Now, regarding “unknown2.” A couple of things make it difficult to decide which cartridge this is.
Firstly, the picture is not clear and it is hard to tell if there is a case-mouth crimp or not with my old eyes. I would bet that it is not crimped. If uncrimped as I THINK it shows, then my specimen has the following measurements:

Head (rim): 0.2995" (7.50 mm)
Base: 0.3015" (7.66 mm)
Mouth (neck): 0.301" (7.65 mm)
Bullet diameter at case mouth: 0.280" (7.11 mm)
Case Length: 0.612" (15.55 mm)
Overall Ctg. Length: 0.9075" (23.06 mm)

I would consider this well within specifications to be the same cartridge as “unknown2.” The question is, what did UMC call it? It appears to me to be the cartridge from Mar 1904 labeled in the UMC Register as the “.30 Cal. Browning,” even though the entry shows a bullet diameter of 0.288". Without pulling the bullet from the case, which I will not do, it is hard to know its true diameter at the largest point. Case mouth measurements are often smaller than diameters of bullet bases.

However, there is a very similar cartridge, also with no headstamp and “U” primer that has the following dimensions:

Head (rim): 0.2975" (7.56 mm)
Base: 0.2985" (7.59 mm)
Mouth (neck): 0.295" (7.49 mm) (measurement taken below heavy roll crimp)
Bullet Diameter: 0.259" (6.58 mm) (measurement taken just about very, very thin line of lead
from half-mantel bullet base. This is a Smith & Wesson-type bullet with half-mantel bullet
having two opposing-lead flanges just above the base of the bullet jacket)
Case Length: 0.6165" (15.66 mm)
Overall cartridge length: 0.895" (22.73 mm)

Unfortunately, the UMC Register, often oddly lacking in technical information, does not tell the bullet type for the 7 mm Browning, produced in July and August of 1908. It does seem to mention (I say “seem” because it is hard to read) that the case length is the same as the .25 caliber Browning, and it IS certainly close to that. My UMC no headstamp, “U” primer .25 Auto round has a case length of 0.6175" (15.68 mm), well within specification tolerances with the above cartridge. Can this cartridge with the heavy mouth crimp and half-mantel, Smith & Wesson-type bullet, be the “7 mm Browning”? I don’t know.

Then there are the rimless .32 APs, one with “UMC” headstamp and “.32 ACP” caliber designation and one with “REM-UMC” headstamp and “.32 AP” caliber designation. But those are for another question, another time.

All dimensions taken as carefully as I can with a Lyman electronic digital caliper.

I know I have not positively answered your question - as I said, this subject is a confusion to me, and many others that I know. From the scant documentation available, it is difficult to be dogmatic with one’s answer.

Edited to correct spelling error only


[quote=“JohnMoss”]Pete et al.

Firstly, I believe it is an error to intimate that UMC auto pistol cartridges with no headstamp and a “U” primer are “prototypes.” In some calibers, they simply exist today in far greater quantity then they would if they WERE prototypes. [/quote]

Please note I said “sometimes found unheadstamped” not all.


Pete - I know. I probalby used the wrong word in “intimate.” Better wording would have included “but unheadstamped, “U” primer, serially-produced rounds were also made.” Or, something to indicate that.

I hope there was more interest in that posting than just that. : )


OH Yeah! Lots more interest. I try hard to absorb most (koff, koff) everything you say.


Pete - that’s more than I do. That’s why I have to research this stuff every time. : )

See you at St. Louis.


Pete, John,

Thank you both for taking the time to provide a wealth of information! I have learned quite a bit and will endeavor to improve any future posts with better pictures ( have to practice) and dimensional data (my calipers are on order).

It has been quite a good first experience for posting questions and it won’t be my last.

See you both in St Louis next week.