The black powder hunting regulations here in Idaho specifically prohibit a muzzle loading pistol and revolver for hunting, regardless of barrel length. (Revolvers because the cylinder is not loaded from the muzzle of the barrel.)
On the plus side, during the muzzle loader only season 209 primers, and powder pellets are prohibited. The regulations specifically limit you to percussion caps, musket caps or flintlock, and loose powder and a round or conical ball that is within .01" of the bore diameter.
Sabots are specifically prohibited.
Unless a flint lock, when the hammer is cocked the cap/musket cap must be visible, too.
I'm not sure if a black powder pistol of the approprite calibure can be used in the "Any Weapon" seasons.