Material limits of HSS thread cutting die

hi there I'm trying to make a custom screw of an uncommon thread and diameter, I made a test piece out of mild steel on my very basic mini lathe but it is too ductile for the intended purpose and permanently deformed with use though it didn't fail, looking for the next steps up in hardness and strength that can still be threaded by hand since the project is too small for any of the local metal shops to take it on, the screw is for the latch on a top break revolver if that gives an idea of what types of shear forces will be applied, would turning down a typical long shank machine screw or bolt work? or are there other better metal options available?