Did something like that with a 6.5 Arisaka once. I had two identical rifles with me at the range and one I had re-cut to 6.5x55. I felt less recoil and thought it was a light load. I jacked it out and when it rolled on the table, it looked it lost part of the neck. I was lucky because the case diameter right in front of the head had swelled to 6.5x55 dimensions. The whole case was paper thin. I never put two different boxes of ammo on the table after that.