Ted, in my long experience with muzzleloading arms I've never known that to be the case, the loading procedure I mean. Nothing would have ever been used to plug the nipples. Had that been done the cap couldn't possibly get fire through the nipples to the powder chamber. Wax was used to plug the individual chambers ahead of the ball to prevent hot gases from blowing back past the ball and reaching the powder, in chambers adjacent to the one being fired.
Patches weren't normally used in revolvers. A lubed wad went in between the powder and the ball, which was seated "naked". Thus, the ball didn't fit tightly enough to prevent hot gases getting by it.
