In an ongoing quest to learn more about converting 9.3 X 74R brass to 3" .410 brass I am wanting some info about annealing the top third of the case. It seems to be pretty much a given that the top third of the case should be annealed before allowing fire forming to expand the neck to .410 chamber dims. After reading up on doing it, and seeing everything used from a $1300 electric induction annealer to a handheld propane torch, I'm left with a question about the process. I see conflicting methods concerning the cooling of the brass after the heating. Some dunk them individually, and immediately, in water. Benchrest shooters, who use the expensive annealer I mentioned above, seem to let the case cool on it's own (in the videos I watched).
I've always been told that to properly anneal an action, or any other piece of steel, it should cool as slowly as possible. Some used to even pack them in lime to extend the cooling down period. Is brass different? If the idea is to relieve internal stresses in the case shoulder and neck, and result in maximum ductility, wouldn't a slower cool down be better than a quick dunk in water?
Brass is not steel, so you can ignore that. But quenching brass is not needed and most competition shooters allow them to air cool. But we are just barely heading them. For this, the cooling method will not be anywhere near as important as how much they are heated.
I built my own annealing machine which allows me to regulate heating fairly precisely. If used after every firing, then minimal annealing is desired and the brass barely gets a blue color blush before it is "done". In your case, a bit more annealing may be desirable, so you may opt for a hint of red in a dark room, but just at the neck. If you really want to push that hard, then perhaps the water quench would be advantageous because it will keep the heat from running down the case into the head region.
![[Linked Image from i.imgur.com]](https://i.imgur.com/qclHjMQ.jpg)
