Smith Carbine Round?

Spent an hour playing/learning on some property I own yesterday before getting rained out. But I found a bullet I can't quite recognize. From what google taught me it looks like a Smith Carbine Round. But that's a Google guess. Can anyone give a more experienced or educated opinion? The bullet looks about 0.50 cal., though I don't have calipers with me to be accurate. The base is flat and solid without indent. The bullet also appears to have rifling impressions along it's base.


Thanks!!!