i have my kentucky flinter which i barely shoot due to BP being harder for me to get. When i have it, i go through it so fast that it gets expensive.
You can buy a 25 lb. bag ( 400 ounces - 175,000 grains - 2,058 85-grain loads) of Jacks Battle Powder (which is non-graphite 3F GOEX) for $275 shipped to your door. That should last you quite a while and costs the same as 100 ounces of that black gold you shoot so much of.