My .40 flintlock rifle shoots really nice with 65 grains of 3F under a .395 round ball, with a 10 thous's patch lube with what ever lube I'm using. I have a couple, including real bears oil and all lubes perform equally well. I have tried reduced loads in my .40 flint and it didn't shot as well as the normal .65 grain load.
James Blue Lightnin'