Can someone offer some guidance on choosing alloys for different uses that must be machined? I'm cutting some acme thread components soon for a stop on the Powermatic mortiser project. What alloy should I use for these threads? It's not a high stress project. Second is a general steel for gunsmithing. Anyone know what would be appropriate for picatinny rails? Might make a replica of a specific historic flash suppressor for an M1 too, guesses on alloys for that?

Obviously I'm a noob at this, but having fun.