Picked up a TC Hawken 50 cal. from an estate sale at a very good price. While reading the instruction manual, it only states FF powders or substitutes may be used. I find this strange. I've been shooting Lyman GPRs over over 30 years and Lyman has always had some type of conversion for using FFF powders or substitutes for their muzzleloaders; usually 10 to 20 % reduction depending upon projectile, Sabot or Round Ball. Suggestions or comments?