Brent;
The majority of my Black Powder use has been in muzzle loaders. With them just make certain the Card wad is a good tight fit & there is no problem with "Blow By" to ignite ant thing in front of it. When loading black for a breech loader it is essential the wad column is long enough to bridge the gap across the forcing cone, from the shells end to the actual bore diameter & that the hard card is a tight fit to the bore.
As I said I have not used plastic wads with black, but have simply never had a problem with Smoldering fiber wads when seated over the proper card wad in a proper chamber for their use. This of course eliminates long cones, much oversize bores & shells shorter than the chamber.
