Make sure that when measuring charges thrown by the Auto Disk measure, that it is done out of the normal loading sequence. It is important that the measure work consistently in the amount of force used to move the disk to the drop hole and return. This is accomplished through consistent press lever operation every time.
It is very also very important to ensure that the Auto Disk measure is seated securely into the Powder Through Expanding Die which must also be properly adjusted. View topic here.
If you are using a chain return system, it must be adjusted properly. This ensures that the disk moves the same amount each and every time the lever is operated. View topic here.
You may want to "condition" the measure by either using powdered graphite on the disks or running the equivalent of a pound of powder through the measure. Powdered graphite is available at most hardware stores (often used as a dry lubricant for locks). If you find that inconsistencies still exist, you may want to wash the disks in warm soapy water, rinse and let air dry. This should help eliminate any static that may have been present.
With 24 holes in 4 disks, you will not get the exact charge weight you require. You will get close, and never get more than specified. Different powders meter differently, some with more uniformity than others. Another variable is powder density. The manufacturers tell us powder density can vary 15% from lot to lot. If you want to get closer to the prescribed charge, get the Adjustable charge Bar, product # 90792. Our goal is to provide a consistent powder charge. We feel this is more important than the exact weight in the charge table. Varying a velocity by 50 FPS, from a book specification, is less important than each round producing the same velocity. CONSISTENCY!
If you are confirming the charge weight with a scale as you should be, there is no problem going to a larger hole to get closer to the specified charge weight. Just make sure you stay between the starting load and the never exceed load. All powder measures will have some variance from charge to charge. Work with the average charge weight of at least 5 different charges.
Lastly some powders do not meter well, Unique powder is one example that meters with "casual uniformity". You may find the same symptom with small flake powder in small quantities.