My p99 is ammo sensitive too. Doesn't like S&B, but loves Winchester. I bought some hi-caps from a guy who traded his P99 in on a Steyr, and he said he had the same problems and put a lighter recoil spring into the package for no charge. I haven't tried the spring, but rather just keep feeding it Winchesters. I can run the S&B's in my other 9mm's.