Wow! Lots of choices out there. I do not know enough about the machining properties of various alloys to choose intelligently.
I have been using hardware store mild steel then case hardening. It can be poor quality. Some of it machines very poorly, galling and leaving a rough finish. Some is brittle yet soft.
For something like a sear, or other lock parts, I would think that some thing homogeneous, tough and heat treatable would be good. All the identified steel I have worked with is o-1 and Brownells spring steel (1075?). I do not want anything that hardens while I drill it. It need to be anealable if I mess up. Something I quench in veggie oil. It need to be workable with common drills, files, hacksaws, and high speed tool bits.
Is my initial guess of O-1 the best choice? I do not want to buy a lot of steel I end of not using. Any help would be welcome.
Thanks,
Scot