The advantage to neck sizing is less working of the brass along the side walls.  Every time you full length size you set the shoulder back and when fired the case stretches to set the shoulder forward to match your chamber.  This work hardens the brass just above the head and will eventually result in a partial or complete head separation.  If your rifle is tightly chambered this may not be an issue, but many Krags have what at best can be called loose chambers.  Google case annealing and every ten reloads or so anneal the case necks.  I just shoot cast bullets at very moderate velocities (1400-1500 fps) and have about 25 reloadings on the lot of brass I am using.  Eventually the necks do split, but nothing lasts forever.  If using a full length sizer adjust it down so it just sizes the neck, if tight chambering then adjust it down a little at a time til the round will chamber and stop there.