Annealing
Heating the case neck and shoulder to soften the work-hardened brass, restoring ductility, extending case life, and keeping neck tension uniform.
Annealing is the controlled heating of the case neck and shoulder to relieve the hardness that builds up each time brass is fired and resized. Repeated working stiffens and eventually cracks the metal, so a brief, measured heat softens the grain structure back toward its original state. The neck is targeted because that is where the brass flexes most during sizing and seating.
The practical payoff is longer case life and steadier neck tension, since uniformly soft necks grip every bullet the same and resize predictably. Done as part of a reloading routine, annealing keeps a batch of cases behaving alike across many firings rather than drifting as some harden faster than others. The head and body are deliberately kept cool, because softening the base where pressure is contained would be unsafe.