Steve is absolutely right on the plastic wads. Stay away if you don't want melted plastic in the barrel.
This is what I use.
Black Powder (the real stuff) 60g measured in a homemade measure made from1/2 inch CPVC pipe
Nitro Card, seat with wooded dowel of about bore size and hand pressure.
1 1/2 brown fiber wads, just tear one in half with fingers. Also seated with wood dowel.
7/8 oz shot
Over shot card wad held in with silicon or waterglass.
A trick for good patterns is a balanced load, same volume of powder and shot. This load has worked well for me when I was shooting Cowboy Action, throws about 5 feet of flame from my double.
CF