Some folks wonder why black powder is not metered the same way that smokeless powder is. To further confuse the issue, both measurements are quantified using the same unit of measurement (grains), even though the measurement processes are quite different. Here is some information which may help clear up the confusion about measuring different kinds of powder.
Both black powder and smokeless powder are measured in grains - but black powder is measured by volume, and smokeless is measured by weight.
The reason is that black powder is a simple chemical compound (made of sulphur, charcoal, and saltpeter) of a given grain size (Fg, FFg, FFFg, etc), and can be relied upon to produce consistent loads when measured by volume. A volumetric measure (one small scoop, for instance) of FFg black powder can be expected to contain the same amount of powder - therefore the same explosive potential - time and time again.
Smokeless powder, on the other hand, is made in many variations - and the little particles of powder are made in many different shapes and sizes. One type of smokeless powder will be composed of small short cylinders, and another type made of tiny grains resembling grains of sand.
Being composed of differently-shaped particles would be enough to cause volume to be an unreliable measure of smokeless powder, but besides that reason there's also the fact that each type of smokeless powder is chemically different from the other - so a pinch of one vs. a pinch of another will not produce the same pressures and burning characteristics... even if each pinch weighed the same.
Now, all that said, smokeless powder CAN be measured by volume - if it's done very carefully and attentively, with a guide to follow. Lee Precision makes low-priced powder scoops for precisely this purpose. One must pay very close attention when using these scoops, because a scoop of one type of smokeless powder will not weigh the same as a scoop of another type.
It's best to weigh several scoops of a given powder to ensure that the weight each scoop contains matches your reference chart, and to ensure that you are getting consistent charges from scoop to scoop.
- Russ Chastain