Many of the traditional type flintlocks will handle up to 110 grains of 2f and 90 grains of 3f in a .50 caliber and it jumps to 120 grains of 2f and 100 grains of 3f in a .54 caliber. This could vary from manufacturer to manufacturer but those are the general guidelines. Some of these values will also vary according to the kind of projectile you use. Those listed are for roundball.