Since you are using the dipper method, you may need to make some different dippers. Take a shell case, say 32 Long or 380 acp. Use a short piece of wire or coat hanger, and make a loop handle about 3 or 4 inches long. Make a few of each. Now find a friend with a decent scale, and weigh the amount an empty case averaged, and mark that dipper. The old way was to drip candle wax into the next dipper and weigh the result. right on down the line. Instead of candle wax I prefer epoxy. Then off to home you go. The Dixie Gun Works catalog used to have a table for standard cases and the amount of Black Powder they held.

Ivan