I believe the current sear would be more wear resistant than crs or 1018. I've never worked with D2, but I believe it is a much better choice than CRS. If you can get D2 up to 64 rockwell, then you have tool quality steel. I think the problem with it would be the tempering process. If you can get a high carbon steel in the annealed state, I believe it would be perfect to work with. It's easy to harden and temper unlike the martensitic and precipitation hardened alloys. Carbon steel can be brought up hard enough to gall HSS drill bits and tough enough to make springs. I'm no metallurgist, but I work with crs and hrs all the time. You could even use crs to make the sear and have one of your buddies use a 70 or 80 series welding filler to build up the area for your engaging surface and grind it to the final shape. I believe that would be hard enough for sear work. Like I said earlier, CRS can be case hardened, but, it's time consuming and to do it to a good depth requires cyanide. It can be done with bone meal and a furnace too, but I would think just a plain old piece of high carbon steel hardened and tempered would suffice. Keep posting your progress, this is the kind of stuff I dig. If you have access to an old leaf spring, they are a good high carbon steel. It would have to be annealed so you can cut it, but it can be re hardened and tempered when you're done.
