This is a cut and paste with the author, Rocky Raab permission about powder measures.
"There are several facts and truths about this issue - some of which nobody believes.
One: Most measures are better with one type of powder than another. Be it flake, extruded or spherical, some measure are liable to choke on at least one. It's just the way it is.
Two: Operator technique is at least as important as mechanical factors when it comes to dispensing consistent charge weights.
Three: The water content of the powder changes, and that affects the WEIGHT of a given charge, but not the actual amount of powder IN that charge. So a measure that's set to dispense 50 grains of powder one day may dispense 49 or 51 grains on another day. BUT IT IS STILL DELIVERING THE SAME AMOUNT OF POWDER! If you change the setting to get the "right" weight, you are actually changing the charge.
Four: It is NOT always that vital to get a charge weight down to the exact tenth of a grain. It can be important in very small charges for very small cartridges, but not in most rifle rounds. Instead, what you want to achieve is ±1% of the desired charge weight or less. For a 50-grain charge, that means anything less than a half-grain either side is not only acceptable, but you probably cannot tell the difference on target. (And that's one that hardly anybody believes, but it is true.)
Five: The only way to get exact weights is to - weigh. That means weigh every charge. You can use a trickler, a spoon or even tweezers, but if you insist on getting right to dead-nuts on, that's the only, uh...way. Or get a digital dispenser which does the weighing for you. (But read #4 again. Really.")Rocky Raab