Mr. Edpert....We have CCH from Rossi to Purdey....from Mossberg to Parker....from Savage to Sauer...from Marbles to Lyman...from Baikal to Boss....from Taurus to Colt....
Millions of firearm parts have been, or are being manufactured and casehardened at industry standard temperatures.
It ain't rocket science.....
And....hardly anyone but an amateur uses a torch as a heat source........... Grant.