Understood.....
I haven't got to the bushing die question yet, as it requires uniform neck thicknesses, to be able to chose the bushing for desired tension....

Just was at the can I take the high spots off the neck by turning and use a standard non bushing die to get better results part of the question..or does it need to be turned to a standard thickness..

(At this point being the average of the thinnest dimension on the cases I have, some lc, some fed,win,r-p,etc..

The idea here is that the neck stays concentric while going in as well as coming out of the size die.