The propellant, that is. It's very useful; for a number of cartridges and loads it's the 'go-to' stuff for best accuracy. And they improved it a few years back so it's a lot cleaner-burning. But it's still a pain in the ass.
I have yet to see a powder measure it'll go through and consistently give the same amount. You'll go along and get anywhere from two to a dozen exact measures and then you'll get one(or three, or five) that are light. Not just a touch, mind you, but tenths of a grain off. Occasionally more. And if you keep throwing charges and checking suddenly it'll be exactly on the setting again. And then may give a few that are slightly high.
Pain In The Ass.
Hopefully I'll someday find a way to cause this stuff to meter consistently and precisely, until then it'll continue to be a great big PITA.