this i found interesting on the cva site.



Pyrodex relates closely to blackpowder on a volume to volume basis, but not the weight of the charge. In other words, a scoop type measure set to dispense 100 grains of blackpowder will dispense roughtly 72 grains of pyrodex "pyrodex is bulkier" This lighter charge weight of pyrodex will fill the measure and provide a charge which is ballistically similar to 100 grains of blackpowder of the appropiate granulation.
Hope this helps those who were asking. I really dont get technical with this type of stuff but ran across it.