i agree on how the powder gets down the drop tube, i "jiggle trickle" by holding the brass pan in one hand and tapping it with a finger of t'other hand. this gives more uniformity to the drop in terms of how much powder leaves the pan at any one jiggle, and the space of time it takes for the next jiggle.
there are so many factors involved in cartridge loading that all need to be done well, not just one or a few. no small task for the impatient or ADD types!