Temper embrittlement? I've had blue tempered plain carbon tool steel be surprisingly subject to breaking on impact. Looking it up (ain't the Innanet wonderful?) I found that steel, alloy in particular, looses impact strength (permanently) if tempered between 250C and 400C. I temper outside that range if I'm gonna hit it. Last time I tempered (W-1) in the kitchen oven, ran it up to 450F (232C), let it cook for about an hour, and let it cool with the door closed. You can't cook too long when annealing.
But all I know, beyond that damned blue tempered thing breaking when it shouldn't have, is what I've read. Google "temper embrittlement" and get confused.
Here's a
Link with a nice graph.
So how impact resistant do you really need it? Dunno, but for a SxS or O/U firing pin I'll take all I can get.
