Howdy KC,
I sent you a PM.
The words "load by volume" can cause a lot of confusion. When a load specifies "grains", the common reference is weight. Loads "by volume" basically refer to the relative volume of black powder (of some specified granulation) as it compares to whatever substitute you are loading in it's place, such as Pyrodex or 777.
The important thing with real black powder is to ensure the volume of the cartridge is filled with some combination of powder, filler, and bullet. How much of which depends on how heavy of a load you want.
Using a 200 grain bullet, I've heard of loads as light as 15 grains and as heavy as 37. Fifteen seems kind of light and 37 goes through a lot of powder in a hurry!