ALL loaded by volume, FOR volume; weight is completely irrelevant to them. Specifically I'm not sure if they use mL or CC.
Loading extruded powder by volume will take advantage of the relationship between the BD & BR. So when the BD shifts a corresponding inverse burn rate change happens. As a wonderful side benefit, you always have a singular volume, so your cases don't have a moving case fill, which will further aggravate a change in burning rate.