Custom gunsmiths have been heat treating parts since the days of Brown Bess muzzleloaders in the 18th. Century, or before. Using a Brinell hardness tester is not rocket science, and neither is using a rosebud torch and some Kasenit powder. The only places that might need to be tempered are the ends where the bushings ride, and those don't need to be brittle- - - -just surface hardened.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!