The disks will throw different weights based on several things such as powder type (ball powders work best in my experience), amount of powder in the hopper, how hard you pull the handle, etc. consistency is key.
Simple things that will help: create a baffle inside the hopper. I use a pice of paper rolled into a funnel so the opening is maybe 1/4" about 1 inch above the bottom of the opening. Pour the powder in funnel and now the amount of powder above the opening is constant, and more consistent charges should follow.
Strive for consistent pulls, each time you throw a charge use the same technique and things should even out. This is where the screw in the cavity comes in handy. Instead of changing disks screw in or out to dial in a charge.
Overall strive for consistency