how do you clean a barrel on a muzzleloader? I mean eventually it probably needs cleaned somehow because all of the burnt gunpowder would build up in the bottom of the barrel. However,the bottom of the barrel is blocked off so you can't run a cleaning rod all the way through it? It looks like some sort of screw at the back of the barrel but I'm not sure if it is designed to come off or not, anybody know? So how do you get the junk out of the bottom of the barrell periodically?