Try as I might, I can't think of any reason MV would increase 100 fps with crush fit casings versus .002" shoulder setback resized casings. I could understand how one might shoot better than the other out of a particular rifle. But I can't figure any explanation for an extra 100 fps MV provided your using the same brand & lot of casings, the same primers, the same charge and Lot of powder, the same case trim to length, the same bullets, the same bullet seating depths, the same fouled bore, fired at same temperature.