I'm doing load development for a 300 win mag. Before I did my ladder test with Noser 180 AB and IMR 7828, I shot 10 sighters/foulers with virgin Norma brass that had been FL resized with RCBS dies. ES was 19 and SD was 7. The ladder test with once fired Norma brass had much more variance in vel, not just do to increases in powder. I've always had problems with relatively large ES (40 to 90) in group testing with the same powder charges. This is the only time that I have shot virgin brass before a ladder test or group test. Question: why would ES be lower on virgin brass than once fired brass??? Thanks for your help.