Yes, I know this is an old thread, but still on the first page, so what the hell.
I had a P40 for a while, it was terrible. Recoil was as bad as is generally said, but that wasn't the problem. The problem is that the gun was unreliable and multiple trips to the KT factory didn't fix the issues. The biggest issue was that the nose of the bullet could (and often did) slam into the bottom of the feed ramp when chambering. This would cause a smile shaped divot in the bullet and could potentially push it back into the case causing a serious over pressure situation. KT was aware of the problem and two trips back to the factory they failed to fix the issue. On the third trip back they replaced all the .40 parts with 9x19mm parts and turned it into a P11 for me (at my request). The only way to actually see this problem was to eject an unfired round that entered the chamber after firing the previous round, it didn't show up with manual chambering. It leaves me wondering how many P40s have been lost to KBs after a lightly crimped bullet pushed into the case when chambering.
The "smile" problem was well known at the time, the K-TOG forum was alive with people talking about the "P40 Smile" back in the late 90s.