this is a black powder firearm. If it is a brown bess firing a 3/4” lead ball, it is probably lethal in freefall. If it is a ten gauge black powder shotgun firing a .775” diameter lead ball, it is probably lethal in freefall.
My reckoning was that if you are out farting around with a black powder rifle now, you are most likely whitetail deer hunting. Everyone I know that hunts deer with blackpowder uses a .50 Saboted, conical shaped projectile.
In much of the midwest, deer can only be hunted with bow, shotgun, muzzle loader and some pistols to avoid this very thing from happening. Population is too dense to use large center fire rifle loads.