Let's put this to rest once and for all.
1. In the process of manufacturing, powder (black and otherwise) is made in batches aka "lots". Because of variables, powder differs from lot to lot.
2. In pursuit of accurate or safe ammo, load development is done by WEIGHT. Mass is mass, doesn't matter how big your measure is. That said with a caveat, keep reading.
3. Once a load is determined, ALL powder is measured by volumetric methods, in both black powder and suppository guns. That's a fact of how the majority of measures are made. Some competitors will dispense a set amount and then use a trickler to bring it up to WEIGHT and they're weighing each charge for maximum accuracy.
So virtually all charges, once the weight is determined, are dispensed by volumetric means. When loading match ammo, consistency is king and that means doing the same thing the same way each time every time. After I work up a load, match ammo is assembled using a volumetric measure but I check every 10th round to see if it's within my predetermined tolerance. Now for the fly in the ointment. Since powder varies by lots, if you change lots, you'll have to verify your load data all over again. I'd bet good money that 50gr of 3f by volume from lot A will weigh different from that of lot B. What does that mean? It means you're using more (or less) powder in your gun. If you're a competition shooter, that matters A LOT. Remember consistency?
Now for "the rest of the story". When we discuss accuracy and consistency, there must be a point of reference for any comment to mean anything. How many times I've heard- "I can hit a deer with my gun", so what, I can do that with a Ford or Chevy. Or, "I can hit a 12in steel gong at 100yds"- really, that just tells me your gun shoots 12in groups, sorry not impressed. In discussing things centering around accuracy, be specific. Group size, loading methodology, testing criteria, testing methodology all are very important. Otherwise, yer just plinking and having a good time. Not a bad thing, but it don't win any matches.