Ekeisler, the bullet's finder, wrote:
> This bullet is .58 caliber.
Your bullet is a fired civil war yankee .52 Spencer Rifle/Carbine bullet. Although that rifle was .52-caliber, it was a Breechloader, and its bullets actually measure about .56" in diameter.
You also said:
> Found in the vicinity of some Confederate Artillery fragments and a fuse. Absolutely no clue why it’s here as there were no reported skirmishes in this area.
The Spencer repeating rifle/carbine became the primary US Cavalry longarm in late-1863. The fact that you found some Confederate artillery shell fragments and a fuze nearby your fired Spencer bullet suggest that the CS artillerymen took at least a couple of potshots at some yankee cavalry, apparently not enough to bring on an engagement big enough to get reported in the official records.
If you wouldn't mind adding another photo here, I'd like to see those frags and the fuze, so I can tell you what kind of shell they are from, if you don't already know.