I assume you are using the Pro Auto Disk. Mine is VERY consistent, from the first powder drop to the last, but I only use HP38, so I am not familiar with the characteristics of your powder. I never bang it around, or throw practice drops, etc.
First, puff the base with graphite, then puff the top of the disk with graphite. I do this every time i have it apart. Then tighten the brass nuts FIRMLY, but not over tight.
Next, screw it tightly directly into the die--don't use a riser. This keeps it from swinging around and loosening as the turret turns.
I weigh the first five drops as I am loading the cartridges. I then weigh # 10, #20, #40, #60 etc. Never more than the width of the scale marker off.
I have a small $30 electronic scale, but would not use it for weighing powder, as it (as I think are most) is only accurate to .2 grains. I believe the cheapest beam reloading scale would be much more accurate. Try weighing the same charge on yours several times, over a period of a few minutes. You may find that it does not weigh the same every time.
As to the MBC 200gn RNFP, 5 to 5.5gn of HP38 is very accurate and easy shooting.
I agree with Lost Sheep, if your powder measure is dropping varying weights, and average of 10, or 20, etc. will tell you nothing.