I found this while turkey hunting Saturday. It appears to be .58 caliber. The case is in two layers and has a shoulder but no rim. There is a copper cap on the back that appears to be a priming device. There is the letter "U stamped in the side of it. The copper cap doesn't protrude past the diameter of the case. reflex264

Dimensions ?

U usually means UMC (now Remington)

SWAG: 41 Swiss reformed into bullet for 58 caliber smoothbore musket.

reflex, that's cool. Is there a dimple in the bottom from a firing pin?

A friend oncce found a case just like that. Never did figure out what it was.

No dimple. It appears to have been unfired and that the bullet had been pulled. There are red flakes that appear to be priming material that fell out as I cleaned it. We already tested it to make sure it is inert. Deffinately not a .41 Swiss as there is no rim that protrudes beond the diameter of the case. This was in a civil war area though no big battles were located here. I will try to take good measurments tonight. reflex264