KS, I don't think that graph you linked showed M4, and I think it showed S7 as being the toughest. SR77 is S7 with awesome heat treat if I'm not mistaken.
You are correct - I edited my post. I left out S-7 when I spoke of toughness. Regardless, that S9V looks like a pretty good steel to me and I bet we some some knives somewhere being made of it - if there aren't already. <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />
