When I do get a wild hair and weigh out charges (usually a rain day operation) I make sure to recheck the jug every time I do so. I have had the weight of the charge actually change a little as the jug gets lighter. That's because some of the fine grains of powder will in time sift towards the bottom of the jug. Also, when you change jugs you start over with the weight average. Normally I will weigh out five charges which I set aside in some speciman cups (plastic ones the pills in the hospital is served to you in) Then when I have the average, the first five charges are basically set that cup back on the scale and add or subtract from it until I get what I want. Then I pour that into the loading tubes.