To echo what Mike said, take a look at the Ramshot and Accurate powder web sites. Western powders distributes both (which is why they look so similar) and they include bulk density and both mixed unit VMD's (same as Lee's; cc's per grain) and metric unit VMD's (cc per gram). But unlike Lee, they list a bulk density tolerance. For some powder's it is as high as ±5.6%. That means the charge you throw from a specific volume measure could be as much as 11.2% different from one lot of powder to the next. So doublechecking the weight is important to knowing what you are actually shooting.
Mr. Guffey's comments remind me to suggest you can use the dippers to learn what a powder measure's arbitrary scale means. You set the measure to throw the same weight the scoop does. You then change the scale numbers by some number of units and weigh the new charge weight it throws. Divide the first weight by the second weight and multiply by the number of cc's on the scoop handle by this number to see how many cc's the powder measure changed when you adjusted it. Then divide that result by the number of graduations you changed the measure setting to learn how many cc's per graduation your powder measure changes. Inversely, divide the number of graduations you changed the setting by the cc calculation result to learn how many graduations you need to change your measure to equal one cc.
As always, your results will be more accurate if you average a number of throws rather than take just one, and if you let the measure settle for several throws before starting and after making the adjustment.
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