That is another really good point. Cheap digital calipers are not comparable to Mitutoyo at all. I had a Frankford arsenal years set years ago and it was really inconsistent. I use whidden shoulder gauge and Mitutoyo calipers these days. However, I think he is saying that he consistently is getting the same measurements.
My first question when I saw the original post was actually, why not just develop your load with brand new brass? I did that last year for a last minute elk load that I was working on and found a 1/2MOA load pretty easily and continued fireforming my brass after I came home with a full cooler. It can certainly be done. It's a little late for you to do that now, but it worked for me and I wouldn't hesitate to do it again when using premium brass.