FMJ, which would be a good, inexpensive practice round. The heavier 124 to 147 gr. Frankly, in this light, little gun, the traditional 115 gr. 9mm loads will do anything needing doing with less fuss and less recoil. Other brands of ammunition tested in the P9 generated considerable degrees of muzzle flash which were distracting to the shooter and not exactly beneficial to one's night vision.
Muzzle flash is an element to be concerned about in defensive pistolcraft.
Cor-Bon has confronted the problem and moderates it much better than their competitors. In the heat of the Arizona summer the P9 carried comfortably in both the pocket and the belt-slide holsters. We would like every semi-auto to incorporate a loaded chamber indicator, especially a DAO that has no external safety. Having to rack back a slide to check if there's a round in the chamber is objectionable. Give us something we can feel to verify the chamber is loaded and the gun is ready.