Annealing. For me the key is to keep it moving. I use a cheap battery operated drill motor, a 1/4" socket adapter and a 1/4x1/2" deep socket. Put the case in the socket and you have a heat sink that prevents the heat from traveling to far towards the base. When you get a uniform color change invert the drill and dump the case in a 5 gallon bucket of water.

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Front sight and squeeze