.58 Caliber Minie Ball?

[noxer800]

Found this bullet along an old wagon/stage road in So Cal. AI identified it as a fired (slightly deformed) 3-ringer Minie Ball .58 caliber. It measures a slight bit longer than 1" and not quite 1/2" wide. Does that ID seem correct? Any feedback would be appreciated.

 

[robertk]

I don't think your ID is correct. The grooves in the rings make me think it's modern, and it's definitely not .58 caliber -- would have to be quite a bit wider. For reference, here's a dug .58 caliber civil war minie ball:

 

[Ism]

My guess is a modern muzzle loader bullet. Looks like something between .35-40 cal. The grooves would either accommodate a sabot or be filled with special grease or wax.
If you look at images online, you will see BP bullets that are very similar.