Now that I am searching for a replacement sear/sear bar for the 25 I'm working on I thought I'd do some research on hand machining the part myself. Not at all likely to do it, but might as well learn something about the process. What hardness does a sear surface need to be to not wear out prematurely? I figure most sears are made from tool steel but there is a fairly large range of hardness for tool steel. General purpose tool steels are O-1 Rockwell C 65, A-2 C 60-62, and D-2 C 62-64. I read that better wear characteristics are found in the A-2 and D-2 grades but the hardness numbers don't seem to prove that out. I'm looking at https://www.hudsontoolsteel.com/technical-data/steelO1 for my basic information. It is my understanding that all of the tool steels purchased at Hudson would arrive in the annealed state and would be suitable for shaping with conventional tools before hardening. Does that mean what I think it means? As in it will be 'softer' as it arrives and needs to be hardened after it is shaped. I realize this option would require heat treating and that is another bit of research. I can reach the required temperatures but I have no idea how I'd maintain the required temperatures for the durations required. Keep in mind, this is a one off proposition. So I will have to make do with what I can get at an affordable cost. Meaning, I won't end up with a full size furnace with computer controlled temperatures. But heat treating is the second part of the equation that can be addressed later if this thought even has a chance of working. Heck, I may find someone locally that could heat treat my finished project. So for now, lets stick to the basic question, what material should a sear be made of and what hardness. I think the general purpose tool steels are a good place to start but maybe there are other possibilities.