I’ve said before that some things are so simple they can’t be grasped. “Co witnessing” of iron sights is one of those.
“Grains by volume” is another. It started when Pyrodex, a black powder substitute, came out. People were accustomed to using a powder measure, used to charge a rifle or pistol with a consistent, known amount of black powder, back in the day when black powder was just “gun powder” simply because there wasn’t any other kind. As we do today when reloading metal cartridges, people way back then used a volumetric measure to easily charge a muzzle loader with powder, but of course someone needed an accurate scale to verify that the volume of powder they were dispensing was of the correct mass. Same thing with metal cartridges. Verify with a scale, then dispense time and again, easily with that volume so you don’t have to weigh each individual charge.
Same thing was done for hundreds of years in the field when using black powder guns– you pour from a flask into a measure that was pre-determined to hold a certain number of drams, or of grains, of black powder.
Then Pyrodex came along with their “volume equivalent” and few seem to have understood any of it since. Pyrodex is a substitute for black powder. It’s chemically different, safer to handle and ship (ostensibly) and doesn’t require the onerous licensing, confiscatory fees and demeaning inspections of premises associated with black powder. By design, Pyrodex will generate approximately the same results in terms of pressure and projectile velocity as the same volume of black powder. This makes it super easy to use the old way– you use the same measures that you always used for old fashioned black powder. Though Pyrodex isn’t nearly as dense, so if you were really meticulous and wanted to know precisely the “volume equivalent” grains of Pyrodex powder you’re using, you’d need to weigh real black powder from your measure. Dreaming up the “volume equivalent” was their way of making it easy to switch to their new powder. You didn;y have to think about– just use the same measure, made of brass or deer antler, etc., that your great great grand pappy used in the War of Northern Agression.
Totally, super simple, right? Use the same volume of Pyrodex you’d use of black powder. That’s it. No; shut up– that’s it.
But now it seems we can’t discuss even real black powder and real black powder alone without people (experienced people even) chiming in about “grains by volume” verses “grains by weight”. That would only come into play if substitute powders were somewhere in the discussion. Otherwise there’s no difference, which we all knew centuries ago (or would have known, had we been alive centuries ago).
“Sure; you verified your charge by carefully weighing it, but you might be off ’cause you’re using grains by weight instead of grains by volume.” I actually got a comment like that today, and I’ve seen it many times before.
Now maybe it would be simpler if Pyrodex loads, just like loads made up from dozens to hundreds of very different smokeless powders, were expressed in actual mass instead of “volume equivalents”. At least I wouldn’t have to explain things when someone tried to tell me that there is something out there called a “grain by volume” of black powder. Then I have to remember that we actually do have something very similar– the milliliter, which is the volume of one gram of pure water, which is what you get from a cube that is one centimeter on a side IIRC. Or was it the other way ’round? Something like that. I forget the actual starting point but last I heard it had been decided that we’d count a certain number of wavelengths from the emission from a certain energy state jump of a certain isotope of a certain element and call that a meter. Look it up and count wavelengths (somewhere in the yellowish range of visible light I think) to calibrate your measuring tape, but please don’t talk to me about “grains by volume” unless we’re discussing Pyrodex or other substitute-for-black-powder loads.