I propose the best way is to use a PID (800F) temp controlled 'pencil' soldering iron with proper stainless or ceramic 'expander' plug tip, inserted into the case mouth. 310 SS won't oxide fast, timing of annealing is the only variable. Only possible contact with case is the neck.
Dipping into a hot pot of silica/sand/etc would work fine but depth control is a problem. Plus I don't want my hand held over a hot pot for any period of time. as others have stated, only loading and shooting will test the results.
I'm trying to remember the name of the genius Israeli engineer/machinist who immigrated to Canada (I think) quickly became wealthy on some of the processes he developed, and has a 16, 18 video (something like that) YouTube series on a long list of processes that are done to bring a product to existence The machines and modifications to machines that he has done to create his home machine shop would make your jaw drop as far as their capability, if not their ability to turn out product on an industrial scale.It's January. I've been immersing myself in machining videos in my spare time.
National house arrest? Around here things are about normal.
I'll repeat what I said earlier: I bet somebody said EXACTLY the same thing to whoever it was that first thought about trying to bake powder coating powder onto bullets instead of simply tumble lubing them. Or whatever.
And if I had too much money on my hands, I'd probably have an AMP induction annealer sitting in my reloading space right now.
But yeah... it is January, it was -20 outside this morning, so yeah, I have some extra time on my hands during this period of national house arrest along with the temperature.
You do have me on that point.
It's January. I've been immersing myself in machining videos in my spare time.