I use mostly 3F for everything but have used 2F in a number of rifles including a .45. worked about as well as the 3F.
I have used 1fg in a bullet gun for a while and got good accuracy.
The gun was the Whitworth/Alex Henry long range rifle and the
bullets weighed a minimum of 485 grains which probably helped with
combustion. Mostly I used 75 grains of DuPont(GOEX) or 75 grains
of Curtis&Harvey"s 1fg which looked exactly like DuPont's 3fg and
gave the same performance and trajectory.
I used only DuPont 3fg in a flintlock rifle,loaded and primed with it
and no problems at all.
Bob Roller