All necks eventually split.
Anneal your necks after the first reloading. I use a propane plumbers torch and hold until the brass gets hot in my fingers. Not exactly scientific, but it is to a count of nine which about 6 or 7 seconds in the flame.
I know of a reloader who anneals every time, and I guess that is because he pays for Lapua brass. Every other time seems to work for a bolt gun, and in a semi auto, anneal with the first reload, then chuck after four reloads.
Machine guns are awesome until you have to carry one.