That is a beautiful rifle AND a nice whitetail!!
I think it was Sam Fadala who said, "round balls kill all out of proportion to their paper ballistics." I've yet to find fault with that statement.
They don't tumble and unless they hit substantial bone they don't slow down very much.
How can you tell if they tumbler or not?! Lol! And remember, smokeless powder IS a black powder substitute!
Beautiful rifle and great buck, congrats!