Interesting discussion.. I just happened to have just read something about the muzzleloading handguns not being allowed during ML only hunting seasons. I do not know the reasoning behind the restriction either. Always thought a ML handgun would be fun to shoot.
This is from the Tx P&W site.
Muzzleloader: Any firearm that is loaded only through the muzzle. Note: A cap and ball firearm in which the powder and ball are loaded into a cylinder is not a muzzleloader. Muzzleloader deer seasons are restricted to muzzleloading firearms only.
Technically, are the handguns you mentioned considered cap and ball? If so, then they would be illegal.