ive killed many a deer with a t/c hawken .50, percussion, with a patched ball.
ive also killed a few more with my knight wolverine, inline .50, shooting saboted .44 bullets.
where i grew up it wasnt uncommon for people to use cap & ball revolvers to take deer.
some states require that a flintlock, or a minimum caliber be used, or it might be shotgun/muzzle loader only for gun season.
my dad has killed 2 small black bear(200lb, 310lb) with his muzzle loader, and one of his buddies hunts deer with a single shot .50 black powder pistol.