In order to determine the optimal neck hardness when annealing brass cartridge cases, we tested multiple cartridges, brands and dies. We ran a range of hardnesses from 85 HV to 125 HV, and did multiple reloading and annealing cycles with each. The objective was to find a level of annealing that is repeatable each and every cycle. The accuracy of our program settings has now been confirmed at competition level by many of our customers. To really benefit, brass annealing should be done every reload.
For more detail on brass hardness and the benefits of annealing, see our study Annealing under the microscope