I am thinking of trying my hand at making a 1911 slide. I have a Slide Casting that I bought from Sarco. I believe that it is 4140 which is an oil hardening alloy. In my review of the prints, it looks like the slide is hardened, at least in spots, to 40 – 46 RC. I am trying to decided between heat treating before milling or heat treating after milling. I have a molten salt pot, and high temperature oven and can do the heat treating. However, I am sure that there will be some warping during the quench. So I am concerned that if I mill first and heat treat second, that I will mess up my milling tolerances. If I heat treat first, I am concerned that it will make it difficult to machine with HSS cutters. The other choice would be to spot harden in only the wear areas. Has anyone out there done this before? How did you handle the situation? Do most people just machine it and forget the heat treat?