Tom Gillman of Hot Springs AR was an outstanding gun maker as well as long time national record holder in c.f. bench and a short time in ML. He shot only FF Goex even in his .40 flinter. Gillman was very pragmatic and addressed his shooting projects using many years as a smith and shooter (including 18 years at amp Perry on both rifle and pistol teams).
Tom tested FF and FFF over chronograph 100 shots each. Same gun, ball, patch, lube etc. I wish he had published his findings. He shared them w me as we split a room near a match out of Jackson MS. His reason was that FFF had velocity spikes of about 300 fps w 3-5 shots out of that 100, as best I recall. FF did not show the velocity spikes. If those all occured in one agg or target ..... well.
Using FF in that .40 flintlock I witnessed him head shoot a fox target 50 plus Xs two years in a row. That's offhand at 50 yards folks.
I shoot FF Goex in all BP guns .32s, pistols flintlock, all of them.
TC