I recall a Civil War guy would come to the grade schools and give a show and tell about the equipment and guns.  This is in the late sixties and he was a way old guy.  He said he had acquired a war rifle that had three charges rammed down the barrel.  Yep in the heat of battle or maybe just a story to impress the kids.  Either way it stuck with me and should I ever buy a muzzleloader I will be wary of multiple charges.  Which rolls right into being wary of double charging pistol or rifle cartridge rounds.