Goodness.
Case brass anneals, or softens, at something like 650-700F, not going to look it up now but that's under any visible red glow in a lighted room. Heating below the annealing temp will accomplish nothing, the brass won't be changed at all.
Brass hardness comes first from the alloy and it work hardens more as we use it. Hardening actually changes the metal's grain structure. Annealing restores the hard, brittle grain structure to something close to the original characteristics, softer but with some springyness. Meaning, good annealing can extend the useful life of our cases If it's done right. Not only will the softer necks not split so fast, they will shoot better AND seal the gas pressue in the chamber better than work hardened brass can.
I have a few .243 cases I've reloaded, hot in a factory sporter barrel with a sloppy chamber, as many as 15 times with no fear of a seperation. They have been annealed twice, and are due again, but they HAVE NOT been FL sized by "touching the shell holder" each time. If they had been conventionally sized some of them likely would have stretched and ruptured after as few as 4 or 5 loadings, as the magazine "experts" caution but don't explain why it's true. There is no justification for our cases to have that much stretch and seperations, even after many reloadings and, if they are properly sized, it just won't happen.
Annealing has no value to anyone tossing brass after a half-dozen or so loadings unless it is brass that has been reformed from another cartridge. Normally, I find that rifle cases which are PROPERLY SIZED will last as long as 20 or more fulll power loads IF the necks don't split! Annealing after maybe each 5-8 loadings will reduce the incidence of neck splitting.
Evenuatally the bodies will split and no annealing can help that. Attempts to soften the bodies would also soften the heads and allow them to rupture. That's not a pretty thought!
Heating brass to a red glow, even in a darkened room, damages the alloy by burning out the zinc. Such over-heated brass is dead soft and will have no "spring back" at all. It destroys neck-to-bullet tension and that hurts accuracy. Proper hardness simply can't be restored after over heating.
Using a HOT propane torch and holding the inner blue cone at the neck-shoulder junction while spinning the case in your fingers will do the job. That will limit heat creep towards the head because you WILL drop the case before excess heat migrates there! The hot cases should be dropped directly into a full water bucket. The water cooling is not part of the heat treatment, as it would be for steel, but to STOP heat from getting to the head and softening it there
Neck annealing in a shallow pan of water will prevent head damage but it is almost impossible to get the brass temp consistant around the full circumfrence of the neck/shoulder in a pan so the heating is uneven. That can and will end up causing bent necks when it's pulled out over a sizer's expander plug - the softer side stretches more - so even heating is not a trivial issue.
Spinning cases in the fingers seems to be best method unless you want to spring for one of the (expensive) motor driven annealing machines.
You can somewhat gage the results of proper annealing visually. It's best to start with clean, polished brass. After annealing, the annealed surface will be discolored but should still have a shiney look. The soft blue blush should only reach a short portion of the case body below the shoulder, maybe an eighth inch. If the heated surface has a dead, flat look the zinc is gone and the neck is too soft.
