Ok to use powder already dispensed.
One trick I found helpful, when the powder measure is all clean, it can build up some static and cause some powder to still stick in the hopper and spout.
Wipe the hopper, and all parts that make contact with powder, with a dryer sheet. You know, the same ones you put in the dryer with a load of wet clothes... Helps a lot!
"Laws that forbid the carrying of arms disarm only those who are neither inclined nor determined to commit crimes. Such laws make things worse for the assaulted and better for the assailants." - Thomas Jefferson, 1776