Sorry I joined the party late. My loaded rounds - with Hornady brass - measure .385. A fired case measures .386. I suggest pulling a bullet and pressing the expanded case into the chamber to see if it fits. I am guessing it is very close. If it?s less than .001 you could possibly find slightly smaller bullets for fire forming. Once fired brass may thin out enough to work in the future. You could also have newly formed brass neck turned on a trimmer tool or a lathe. My chamber was cut by SSK in 1981 and has seen a lot of action.