Actually you shouldn't weigh black powder or it's replacements like pyrodex, clean shot, or 777. You should measure them by volume, not weight, it's more accurate. The weight of these powders can change with temprature and humidity. Measure 100 grns by volume and then put it on a scale, I bet it's not the same. And if you work up a load during the summer, then weigh out some charges in the winter you may get some different loads. Unless you pre weigh them in a controlled inviornment. At any rate you should check the volume weight to the measured weight to make sure they are close. This would keep you from having an accidental over charge.

smokeless powder is not the same, it can be measured by weight.

Paul