I just got a Kel Tec PF9 for Christmas, and while reading up on it on the Kel Tec forums, the factory itself does not recommend +P ammo, most use it for carry. I'd never given it much thought for my Sigma, hadn't read anything either. Was at the range today, mainly breaking in the PF9, ran about 50 rounds through the Sigma, (practicing drawing from the holster), after I'd finished up the range ammo, fired a mag of Winchester 115gr +P+, quite a difference back to back, those suckers have some 'pop' to 'em! I've decided to try some 124gr and maybe some 147gr standard pressure HPs in the PF9, safe for the gun, and I can practice with the same stuff I carry. Heavier slugs, better penetration, not as much recoil, helpful with a light gun. I guess I'll go the same way with the Sigma. After shooting about 200 rounds with the PF9, the Sigma was a JOY to shoot, not that the PF9 was bad, but it is a bit 'snappy', the Sigma sure is comfortable, and the trigger pull seems shorter now, imagine that!