A#1, when a person starts working with smaller and smaller particles, the particles begin to react to small electric charges of static electricity caused as the particles move around. This causes the particles to move or relocate themselves to unusual places, as they are poured from their container, which would mean they will not go back into the sample bottle or stay in the pan of the scale and in general will go where they go due to the charge. Or, the particle could maybe contaminate your ammunition loads. You are staying on the safe side by using your powder scale just for powder as if a round does not ignite properly odd pressures could develop sending the projectile down range without uniform pressures behind it.
Every time I remove my gold from its vial, the 100 mesh or smaller particles, do not just fall down onto the pan or paper, they fall outside of the location of where the heavier particles land. As whatever is mixed in with the gold (dirt, hematite, magnetite, etc.) as it moves from container to pan/paper/etc., it can fluff out and away anywhere..............63bkpkr