Case blackening is normal. The tighter your gun is the less residue you'll have. Remember this is not all bad as the tighter the fit the more prone to failures. Loose guns are dependable guns. Don't worry about black residue on your cases. Faster powder will help, but won't make it go away. HS-6 is a very good, accurate powder, but has a reputation of being dirty. I use what ever I can find cheap as long as it works for the caliber. When I store buy I use TiteGroup.