30 years ago we were all told to use FFF in .45 caliber and under and FF in .50 and over...Fact is, FFF burns a little cleaner than FF...I use FFF in both of my flintlocks (.40 and .54), this way I can also use FFF to prime with...I also use FFF Goex in my inline, just don't feel a need to have 3-4 different powders on hand...