Help to ID an Inside Primed Cartridge


I don’t know how to ID the below cartridge because I don’t have enough good references.

It is inside primed (non-magnetic) with a flat nosed bullet in a copper case.

The dimensions in inches are:

COL: 1.378
Case Length: 1.033
Rim Diameter: 0.661
Base Diameter: 0.565
Case Mouth Diameter: 0.542
Bullet Diameter Above Case: 0.517

It looks to be close to a 56-52 Spencer but I am not sure. There is no headstamp.

Thanks for any information.


If the case length is 1.330" and not 1.033", then it could be a Benet primed .50 Cadet, although the bullet doesn’t look right - too short and the nose flat shouldn’t be so wide. If it is actually 1.033", then could it be a reloaded shortened Benet primed .50-70 or .50 Cadet case? The rim and base measurements appear to match these two cases.

Hi Guy,

The case length is correct at 1.033 inches!

There is fairly heavy crimp on the bullet as well.

This one has me stumped.


That heavy crimp is also bothersome, suggesting that the case has been shortened and then loaded.

It is interesting, but it’s hard to avoid the feeling that someone helped Frankford Arsenal out on this one. JG

After looking at this cartridge and examining its dimensions again, I think this was a converted inside primed 50-70 donor to make a 56-52 Spencer. The dimension are very close to the 56-52 rimfire cartridge. It must have been reloaded quite some time ago based on the patina of the case and bullet.

I ran across an article on the web which discussed converting 50-70 cartridges into 56 Spencer cartridges which leads me to believe this practice may have been known for quite some time. Although the article discusses cartridges for centerfire cartridges using rifles with converted breechblocks, there is no reason the same cartridge conversion could not be made with inside primed ammunition.

Here is a link to the article if anyone is interested.

Thanks for all the input.



Being an ex Civil War and Indian War re-enactor I had one of the converted Spencer carbines and handloaded my own cartridges from the original 50-70 shortened brass. But in all my years of martial arms collecting I never encountered a rifle or carbine that had been converted to CF prior to the re-enactment craze. And Flayderman makes no mention of such a thing either. But that , of course, does not prove that they do not exist.

In 1869, Springfield Armory produced a very few single shot pistols with Allin-system (trapdoor) actions chambered for a 50 caliber CF cartridge. These pistols are very rare and even most advanced collectors have never seen one. Perhaps your cartridge was one intended for that pistol?? If so, it would be a rare bird indeed.

Just a SWAG on my part.


Thanks Ray. You provided some very interesting insight into something I never heard of before.