A friend just sent me a CRKT M16-13Z. I think they have switched from AUS6 to AUS4 for the blades in the zytel handled M16's. I didn't see any markings on the blades as to which steel is used. Is there any way to tell? I have several carbon fiber and titanium M16's that I think have AUS8 blades. I have no complaints with them. Is AUS4 a big downgrade from AUS8 or 6?