Is there empty space in a casing? - Part II

A few days ago there was a question: "If powder brand A says use 4.7 grains and brand B says use 8 grains, what's up with the difference in empty space in the casing. Is there empty space in a casing?"

There were a lot of good answers and many answers touched on the correct answer. I would like to expound on the correct answer.

Yes, there is empty space in a casing sometimes. This depends on the density of the powder being used. Density implies a given mass within a given volume, that is to say, weight of the powder versus the space available within the casing. Example - given a pound of lead and a pound of feathers, both do not occupy the same volume (or space) because their density is not the same. Think of it this way, if you filled a gallon milk jug with 1 pound of lead and also filled a gallon milk jug with one pound of feathers, which one would be fuller? Powder is no different.

Fast burning powders are usually more dense because their grain sizes are comparatively smaller to promote faster burning. More grain do not fit into a case because they burn faster, it is because more grains can fit into a given case size. The more grains that can fit into a case of given size, the more it will weight.

This is exactly the principal behind volumetric powder measures. They determine the weight of powder based upon the volume the powder occupies.