I occasionally load black powder shotgun shells, and I recently came across something I found interesting. A published load from the Lyman Black Powder Handbook listed a load of 100 grains of FFFG under 1 1/8oz of shot for a 3 dram velocity of 1200 fps. 3 drams is in fact 82.5 grains, a 17.5% difference from the dram designated velocity, to the velocity of a load of FFFG Goex. It seems then that Goex must be weaker than the powders used at the time the dram designated velocities were established. My question is, by how much? I would like to have some idea as to how much I need to compensate for the power difference to get the listed dram equivalent velocities.