I have what is suppose to be a Spencer blank but I’m now not sure. The rim and head are correct dimensionally but the case length is 1.150. The case is headstamped U, it has a rolled crimp with a buff colored wad. All the information that I have shows cases with a length shorter than the one I have. Is this a Spencer or something else?
Thank You Carolyn

What is the rim diameter of your specimen? It should be .63 - .64 if it is a Spencer. I suspect yours will measure around.70 at the rim which would be the correct diameter for a 58 Miller blank.

The Rim dim. is .635

The 56-50 Spencer case is 1.150" long. You have a case-length blank typically used to train Cavalry horses.

Or, it could be a shot cartridge. You’d have to weigh it to tell.


This headstamped UMC cartridge dates from the 1880s or later, so the days of the Spencer as a cartridge for military use were in the past. Frankford Arsenal did produce a blank in 1870 for the Spencers, but the case was short (about the length of the 56-56) and the loading was evidently intended to be used in any of the Spencer military caliber chambers. Jack


Did you find out what your cartridge is??


I believe that it is a Spencer, I checked other cartridges and I can’t find anything that is close to the dim. It is a blank and not a shot cartridge. The only thing that bothered me was that I’ve only seen cases that are shorter in length.
Thanks for all the help


Any chance of getting a picture of it?

Here are a couple pictures

Hi Carolyn.

Check the head and rim dimensions against a 12.17 x 42 R Swedish rimfire. This looks very much like the blank and the case length is right. It does not have that ‘American’ look to it. I have two Swedish blanks that are similar, but the both have cork top wads. They also used horse hair which is what yours looks suspiciously like. In that regards it is different from mine. Sorry I no longer have a 56-50 spenser nearby to compare measurements.

When I was collecting American rimfires, I never had a US made blank that looked like that. That is not to say it’s not US, but my money is on Sweden.


The case has a U headstamp and the rim and head dimensions are both .010 bigger than the Swedish round.

Carolyn, the rim diameter is too small to be cut down .50-70 rimfire case, which as far as I know only exist with this headstamp as a board dummy. Please, can you double check the rim diameter and also tell us the head diameter?

The rim is .635 and the head is .560

Carolyn, the dimensions of this case are consistent with a UMC impressed “U” ball loading which usually has 1.159" case lenght. In my opinion this is most likely an improvised blank using a pulled down cartridge.

Hi Fede and Carolyn.

Sorry, I missed the headstamp. Fede, the crimp looks factory. The wad does not, so I don’t know what it is. I have a number of UMC centre fire rounds with exactly the same crimp. I no longer have any rimfires to compare it with, but do remember Spenser rounds having the same roll over crimp. The wad is what is giving me the problems.
Since I got rid of my US rimfires about 20 years ago, I don’t recall whether I had a blank like that or not. Perhaps an e-mail to Vic Engel with photo’s and dimensions would be in order.


My husband was looking for something else when he came across a picture of this cartridge in a book. The American Cartridge on page 119 number 4, the only real difference is that it has a pink wad.

Carolyn, you are absolutely right, it looks the same as the one pictured in Suydam’s book. Maybe the original wad was missing and replaced with this furball?