I'm a full length sizer but I have 3 30-06s , 4 12ga's , 2 308s , 2 357s , none of them seem to cooperate if I don't . My 8 mm mauser only gets the neck sized though . The 8mm is 1 of 1 and a mil chamber of war diress . The idea in neck sizing is that you don't work the whole case and with annealing you can extend the case life . If you have an "odd" chamber (i emaximum size) each time the case is fired it has to fill up the chamber too . In the "odd" chamber neck sizing can improve your groups . Full length is a nessecity if you shoot an auto or more than one gun or chamber in the same cartrige . In the end try it both ways if accuracy improves from necking you win and your cases may shoot 3 more cycles . If you have trouble chambering your rounds go to full length .