Originally Posted by Uncle Bubba

You may be right on this fact, I don't know anything about round stock. But I do tinker with forging steel for Knife making. I've played around with tempering to different Rockwell Hardness levels through the years and always find that if I get the steel to hard it tends to not just break but kind of explode and shatter when it goes. I've also found this to be the case on Grade 8 and harder bolts. It looks just like a glass rod that has broke.

So I'm wondering if you could harden this anymore either by cryogenic freezing or by heat treating.