Been loading Black in 45-70 and 45 Colt, you can't overcharge BP. I don't remember how many grains I use but if you figure out your seating depth, then fill enough BP so that you can compress the load about an 1/8 inch or so. If you use a wad, figure that in and use the wad to compress, don't use the bullet to compress. #1 Rule - NO Air Space between bullet and powder under ANY circumstances!