I've been making large bore reloadable rimfire brass from centerfire cases lately. I had a damaged 50 cal centerfire case, (Starline .56-50 I think) laying around. So I got wondering if there was a .50 rimfire case that I could make from it. A quick look at COTW revealed that a .50 navy rimfire pistol cartridge for the m1865 navy rolling block pistol was short enough to make from the damaged case I had. So just for fun, I set out to make one.
The original cartridge is similar in diameter at the rim and base as the 50-70 and other. 50 cartridges of the era. But the case length is .850" - .860". So I trimmed this one to .850", then converted the case from centerfire to rimfire.
It was originally loaded with a short, 290gr bullet over 23gr of black powder. Digging through my 50 cal bullets I found a Lyman 515139 bullet weighing about 340gr. It looked pretty close, but was too long and heavy. So it was chucked in the lathe and the bottom band and grease groove were turned off. This resulted in a pretty usable substitute weighing 285gr.
Unfortunately I have no pistol to shoot it in, but it looks impressive :-)
