[Berk]

I got this from another site.
There is a bit of difference between the pellets and loose powder. Because of the added inert ingredients to form the pellet shape and hold the pellet together, it addes some mass to the overall volumetric charge, which is controlled by purchasing an equivalent powder charge in pellet form.

Loose powder doesn't necessarily have these ingredients, and so have less volumetric mass, which will cause a lower volumetric measurement from larger individual particles (what is used to measure black powder, not a physical weight), so in essense a 2F loose 120gr charge is the equivalent to 150gr volumetric charge in pellet form. As you switch to finer grades of blackpowder (3F, 4F) you are getting more a more dense charge for the volume equivalent, so you'd use less 3F than 2F, and even less 4F over 3F!

FFF t7 is in smaller granules. as a result, more of it fits in a given volume of space. When i set my volumetric measure to 90 g., i get more weight of t7 powder if i fill it up w/ FFF t7, than I would if I filled it up w/ FF t7. So the same volume t7 FFF will give you higher velocity than the same volume t7 FF because there is more powder and less air space w/ FFF. theoretically ....

I wont post the other site unless I get the OK.