When ever you size a case and then shoot it, you are fire forming it. You are correct in not resizing it. The chamber of the NEF 38-55 is such that 379-380 bullets don't need resizing, at least at 38-55 pressure levels. Don't resize, just run the case into the expanding die to bell the case mouth, load and then runt he case into the sizing die, but only enough to get the case to chamber. Turning the die into the press 1.5 -2 turns is enough. More than 2 turns is too much.