I dont use anything other than blackpowder to fill chambers in my Colt Walker just 55 grains of black powder a .44 wonder wad and a .457 ball.
In my flintlock .520 all steel Scottish pistol I use 40 grains of black powder a 10 thou lubricated patch and a .500 ball.
Most satifactory and enjoyable to use.
If you buy a replica at least use an original load in it.