First, did you clean it properly? I use my old Hornady cleaner and dry lube spray on my powder measures (air dry, don't wipe off). Hoppers get washed with a rag of warm soapy water and allowed to air dry (don't wipe off).
Next, you need to cycle a hopper full of graphitized powder (or even simply graphite powder) through the measure to get parts properly coated.
When you add powder to the hopper, the powder must settle. This can be done by gently shaking the measure for several seconds. Then, throw at least ten charges (and return them to hopper) before you ever start to weigh charges.
With a bench-mounted measure, you rotate the handle and Tap-Tap at each end of the handle throw to help keep the powder settled and knock powder clear of metering assembly.
As Lee says: Always make an uninterrupted up and down stroke when expanding or charging the case. If you become distracted and reverse direction, a double charge could result.
With a press-mounted measure, you may have to tap/tap the measure manually every so often (say with a handle of a screwdriver or such).
Some people find that an aquarium pump or vibrator works wonders. Some people find a baffle works wonders. Neither has worked well for me, but my measures work very well without them.
Always verify the appropriate drum/metering assembly is installed—this happens with other measures that have a couple of metering assemblies
For rifle cartridges: Select proper Charging Die
Allow 1 second per cc for charging and dispensing the powder charge.
Check charge weight every 10-25 rounds until you are confident the measure is consistent.
With a progressive press, use a powder check die that will freeze the press. A powder cop die is the easiest thing NOT to look at. I like the RCBS Lock-Out die.
PS: my bench-mounted PPM is the most consistent. My Hornady L-N-L and Lee Auto-Drums are next. My Dillon measures are fine, but not quite as consistent. ANY of them are more than adequate.