Oh jeez, I knew this was going to come up as soon as I mentioned weighing the powder charges the measure throws.
Volume or weight, IT DOES NOT MATTER!
Most of these type of powder measure have a slide on them, and they usually have some numbers inscribed on them. Like this:
So what do you think those numbers mean? Grains Volume? A mythical unit of measure that does not exist in any scientific tables?
Here's how it works. You set the slide to some number. This one happens to be set to 30 grains. Back when these things were being manufactured, the prototype was set up and the number was inscribed at the spot where a charge of KNOWN WEIGHT would be measured out by volume. Then the manufacturer went to town and produced a bazillion of them. If you are using real Black Powder, and set the slide to 30, and then weigh the resultant charge, it will weigh very close 30 grains. Will it be exactly 30 grains? Probably not, because not all brands of Black Powder weigh the same. I keep a chart in my loading notebook of the actual weights of known charges of different brands of powder, and they do not weigh the same. In addition to that, the weight of a known volume of powder will vary by the granulation, because finer grains pack more densely than coarser grains.
But in the grand scheme of things, IT DOES NOT MATTER. Set the powder measure to one of the scribed lines and fill the measure to that level. Then pour it out and weight it. I double dog guarantee you the weight will be somewhere close to a convenient number, like 10 grains or 20 or 50. No, it probably will not be dead nuts on that number, it may even vary by a few grains. IT DOES NOT MATTER! This is not Smokeless loading where an overcharge of 1 grain of Whiz Bang may blow up the gun. Give or take a few grains of Black Powder simply does not matter unless you are shooting BPCR and are trying to consistently hit a small target at 500 yards. And guess what. Most of the guys who shoot BPCR actually weigh their charges, they do not rely on a volume measure.
This whole stupid grains/volume thing started when Pyrodex first came out. It weighs substantially less than real Black Powder, but it was formulated to have the same energy as a similar
volume of Black Powder. So when using Pyrodex, one needed to measure it out by volume so the charge would be similar to a known charge of real Black Powder.
Set the powder measure on one of the scribed lines. Fill it with powder. Dump it out and weigh it. Do it several times so you can average the result, because it will not be the same every time. Then fudge the number to the nearest whole number and scribe it on the measure.
Repeat for each scribed line.
P.S. I go through close to 20 pounds of Black Powder every year in CAS. I load 45 Colt, 45 Schofield, 44-40, 44 Russian, and 38-40 with Black Powder. Yes, I use a powder measure that portions out the powder by volume, exactly as it was done back in 1873. No, I do not take the time to weigh each charge. But I do keep a notebook of what the charges are. Guess what unit I use? Cubic Centimeters. A scientifically accepted unit of voulume. (Sorry, I have not converted to milliliters yet.) And in my notebook I keep track of how much each CC measurement of each brand and granulation of powder actually weighs. Guess what else? Even with the same brand and granulation of powder, it varies over time. This is not Smokeless powder where great effort is made to keep the chemistry exactly the same year to year and lot to lot. It is Black Powder, and the actual weight by volume varies over time. That's why the BPCR guys will requalify their loads when they buy a new lot of powder. Does it matter for relatively informal shooting? Not at all. Even if a slide type powder measure is throwing 52.25 grains when the slide is set for 50, IT DOES NOT MATTER. Set the measure the same every time and you will get all the consistency you need for accurate shooting.
But the big point is that for REAL BP volume is supposed to equal weight.
