Just as Oldbloke said...
Definitely don't over heat them.
When brass gets too hot the zink can burn out of it leaving you with copper, it'll become too ductile.
A general rule of thumb is that in a dark room with only the light from your butane flame the brass shouldn't get no hotter than a barely visible dull glow.
Do not heat more than the neck and just beyond the shoulder.
Heat evenly while slowly rotating.
Quench in water instantly when a very dull glow is present (only visible in a dark room) to stop the heat travelling any further down the case... some say quenching is unnecessary? I like to do it just to be sure.
I hold my brass in a deep 1/4" socket that leaves just the portion exposed that I want to heat sticking out, I rotate it slowly with a cordless drill.
Or you could go all out and buy a killer machine
- 20210225_220321.jpg (86.24 KiB) Viewed 2168 times
There's a thread on annealing here
viewtopic.php?f=3&t=9849