No matter what, you're dealing with an approximation.
It's always been my understanding that traditional volume measurements were based on FF grade black powder - that is, a 100 grain volume measure should throw 100 grains weight of FF black powder (i.e. weight and volume are the same). But because other grades of powder and different subs have different densities than FF black powder, that same 100 grain volume measure will throw different weights of each of those powders. Even then, I doubt that 100 grains volume of two different manufactures black powder, say FF GOEX and FF Swiss, would weigh the same.
Even with the same brand of black powder equal volumes of different grades will not weigh the same, and equal weight charges will have different volumes. For example, 95 grains weight of GOEX FFFg fills my TC U-View measure to the 105 grain volume level, and 95 grains weight of GOEX FFg fills it to the 100 grain volume level. Now with Triple 7 FFG, 95 grains weight will fill that same measure to the maximum 125 grain volume level, and I have to tap it down to make it fit.
Adding to the confusion, there does not seem to be any industry standard for volume measures. Set on the 100 grains volume mark, my TC U-View measure throws a charge to fills my old unknown brand brass measure to the 95 grain level.
So, probably the only valid way to determine load equivalents among different powders is to go by velocity. If you have a load of Pyrodex RS that shoots a certain bullet at 1600 fps, then you can experiment with GOEX, Triple 7, etc. to find what load of those powders push the same bullet to 1600 fps. Then weigh the charges of each powder and you have equivalent loads for that velocity.
Simple, eh? :lol:
