Not responding to anyone in particular, just babbling:

BP volume powder measures are designed/calibrated to throw the same actual weight of BP...ie: a 100grn measure of BP is 100grns weight of BP.

TheBP Subs are usually a different weight...they're designed PHYSICALLY to take up the same amount of volume even though 100grn measure of Pyrodex RS only weight 72 grns or something.

Energy wise, it still equals the 100grn thrown charge of Goex...I assume otheres like 777 will weigh differently toobut they're all benchmarked against a volume measurement.