Like most belted cases they respond best when you size to just barely bump the shoulder like beltless cases but you gen into trouble when the base of the case has expanded to where chambering becomes difficult, what to do !?
Normal reloading practise dictates that you should lower you sizing die to reduce the case dimensions further thus allowing easier chambering of coarse this also creates more headspace so your methods will be a compromise in order to achieve some harmony.
The ideal method would be a die that only sizes the base and one for the rest of the case of coarse this combination does not exist,.....kinda! There is a company that makes a resizing die for the base (whose name escapes me) of belted cartridges and this with a combination of either a neck, body die, collet die or full length die would make a great combo for precise reloading of belted cases. Unless you are full length resizing these difficulties will always be present in belted cases, depends on the chamber dimensions, location of belt to shoulder and diameter of fired case at base with those of the reloading dies.
Hope this helps.
bb