Weighing Cartridges to measure powder variation is an exercise in futility though. Brass varies plus and minus 2-5 grains or more, and so will bullets. So you will never be able to see how accurately the measure is throwing. You will need to weigh each charge for a good number of the first loads, to assure the accuracy, then weighing every 5 charges or every 10 chages and so on.
+1. I weigh the brass (tare/zero), and then throw and weigh three separate charges. Periodically, I weigh the a thrown charge during press operation to be sure that the rotating hopper/charge is the same as me sitting there throwing multiple charges on a motionless turret press.
If you are using W231, the auto disc will be pretty accurate. W231 is a "ball" powder, and meters very well. If you pick a disc in the middle of the load range, you will produce decent rounds even without a scale. According to my scale with W231, they usually produce a load that is low by about .2gr from their published amounts (on the info that came with the Lee dies).
I was in your position (new press, no scale because the Kemph kit did not come with one), and I read and reread the auto disc/W231 charges in the table, produced a graph to interpolate between the published points, figured out how much I wanted to charge my .40 S&W loads, and then used the appropriate disc off the chart. It all worked well, except that I started at the lowest charge level and the ACTUAL charge level (after later getting a scale) was about .2gr lower than I predicted.
So, I was .2gr lower than the minimum, and failed to cycle my auto about every eighth or tenth round.
What I am getting at is that, if you triple check your work and really know how to use the auto discs (vs. just sort of understanding how they work), you could go ahead and start making rounds
