If you got the powder measure from RCBS,, meaning a Uniflow,, you should not be having a serious issue. To get repeatable powder charges,, you will have to rotate the handle/drum exactly the same way each time. I can vary my charge by simply changing the amount of force, or tapping etc of my handles when loading.
And as asked above,, what is the amount of variation you are seeing? What caliber? Pistol or rifle? Type of powder?
If you are loading match types of rifle loads,,, where weighing each & every charge is normal,, then most competition shooters throw a slightly light charge,, then "trickle" the rest into the scale with a powder trickle.
If you are just reloading hunting or target shooting rounds,,, a small variation in the charge isn't a problem,, unless you are already maxing out the charge.
More details will help!