I am playing with the idea of trying to neck down some 375 rum brass for use in a 300 rum to cut down on neck clearance. I have heard its not a goot idea to do this kind of work in a bushing die and I should use a FL sizer. I am guessing i would have to get a 338 rum sizer to neck down in two steps(338 then 300) and then neck turn to uniform to about a .016 to .017 to come up with .003-4 clearance and see if that helps accuracy any. Initially this would just be a test and I would sort through and take 20 cases to try. It would be nice to just buy a bushing to do the job. Any recomendations? Right now my necks are showing about .0142 thickness(fed brass) and Im showing a min neck clearance of .010", I measure .009 and added .001 spring back.