I use two scales to confirm weights. I only have one die set but I decided to try full cam over to see if I could set the shoulder back further on the cases that were sticky and they did not reduce at all with my comparator set so I’m at max shoulder setback with my current lee shell holder. I have a Redding shell holder set on the way that should help.is it the same lot of brass? Hopefully that are from the same lot and not mixed brass, and are you trimming to minimum trim length by the recommended standard.?
And how reliable do you believe you scales are? Also, you mentioned changing your die setting, this could account for some differences in your findings. Always remember, only make ONE change at a time. Otherwise you'll never know which change affected your test results.
The heavy bolt lift, cratered primer and ejector marks would have me concerned.
Just some things to consider.... my .02 cents