I too have noticed there are variances between different manufacturers so I decided to standardize on TC's adjustable brass measures and use them exclusively..
While a particular charge might actually be something slightly different from the setting, as long as I set up, zero, and only use those measures, I'm consistent.

I also have good quality weight scales for my centerfire rifle and handgun reloading, but have made the concious decision not to "moderernize" my muzzleloading hobby by using those kinds of approaches for basic things. I've got a safe full of top quality rifles with high end Leupold scopes that shoot bullseyes at distance all day long...been there, done that...no challenge any more.

I'm not a purist and don't wear period correct clothes or any of that ...but I at least want to live by a few of the blackpowder basics like staying with volume measures, black english flints, real black powder, patched round balls, etc, etc, like our forefathers did...no better sense of accomplishment than to lay a flintlock back down across my lap, see the smoke curl up out of the vent, with a nice big 8 pointer laying in the leaves 50 yards away...no slam on others...just my personal choice.