I started with 85gr pistol powder and worked my way down to a decent group which ended at 55grains.
When rifle grain was still available I used 85gr(volume) with the same roundball which produced a nice and tight group at the same distance. I chronied the rifle then at 1700fps average if I remember correctly.
The new stock of powder which is on the way to the supplier will only be available in one grain, pistol and rifle in one. The guys who produces the powder were scaled down due to bad economy the past 2 years.