The process of treating brass cartridges with heat to eliminate cracked necks or produce uniform neck tension as practiced by cartridge reloaders that is described as annealing, is not annealing.

Annealing is the heat treatment of metal for a time determined by section thickness and temperature according to the alloy phase diagram, that permits re-crystallization of the metal matrix, from a finer crystal grain structure to a coarser crystal grain structure.

What cartridge reloaders do when they heat their brass is not annealing, it is stress relieving. It is sometimes referred to as stress relief annealing, but the word annealing is misleading and has nothing to do with the process.

The time at temperature is simply not enough for crystal growth to occur, and in the few seconds at temperature for brass case "annealing", no annealing actually occurs.