Well it isn't that simple. There is FFg in Swiss, GOEX, Wano and Schuetzen just to name a few and they are not all equal. They also all have different burn characteristics.

Just like smokeless powder you are going to have experiment a bit to find what works. But that's half the fun of shooting these old guns.

Do some reasearch and see if you can identify the powder used and the velocities obtained. Then using the same grade powder buy a lb of several different brands and start testing and see if you can duplicate the load.