What you're seeing is that the once-fired brass hasn't fully formed to the chamber. Not unusual. What I'd do is take the longest case and bump the shoulder a thousandth (less than .002" anyway) and size all the cases at that setting. Write down the number so that after the second firing you can remeasure and see if the cases are still growing to fill the chamber. If so, repeat the process. Usually I find the longest cases from the first firing are pretty close and if a second die adjustment is needed it's just a couple thousandths.