Shootall,
I'm no expert, by any stretch of the imagination. I am told that the longer pressure peak of the .40 S&W pressure curve contributes to the increased slide velocity of the cartridge over the 9mm. That is: Pressure remains at a relatively high level for a longer period after the barrel unlocks from the slide, driving the slide at a higher velocity in recoil. It would appear to me, that in the Glock, (Mdls 17/22) the unlocking occurs at the same point in rearward travel. The only thing I can say with absolute certainty, is in my guns, the .40 is showing the wear well before reaching the round count of the 9s.
Savage