This is something that didn’t happen to me until now and I wonder what the cause is. I had many split necks in the past but always in parallel with the neck and never like this. This happened to a batch of 20 cases and all of them show it to a different degree and length as shown in the pic. These are 6.5X55 PMC cases with about three firing before this one. The cases were not in use for about fifteen years but annealed just before this last reloads. Two loads (10 and 10) both were using mid-range book loads of RL-15 and jacketed bullets. (Hornady 100sp @ 2860fps and Sierra 140BTSP @ 2450fps) The rifle is Husqvarna M38 that never showed this in the past.
The way I annealed this brass is no different than what I always do and that works well for me. (Propane torch for 4-5 second, air cooled etc.) I am aware of PMC brass quality and it is pretty obvious to me that something is wrong with the brass, but what is it, and why is this split direction?