Definitely a cool bullet. Without a diameter measurement guesses at the caliber are guesses since they came in several sizes. Like TMD says it could have been used by a civilian hunter. This was actually pretty common in the rural areas of the south and west. Remember Grant said all the southern troops could keep their rifles so they could hunt for food which was in such shortage back at their homes. As the government phased in breech loading rifles to the military they sold off most of the muzzle loaders as army surplus and poorer folks used them for hunting all over the country for years after the civil war. Since you are near civil war activity it could well have been dropped by a soldier enroute to a camp or battle, you could look up and see if troops were marched through your area. Hope you find a lot more!!