I had a P9 with a longer slide, and ported. Don't remember the model, but it was a .40. It Kaboomed on me. No harm to the gun, and just a little shrapnel in my forehead, numb hands, and gouged glasses.
Gunsmith determined that it would indeed fire out of battery. You could see the barrel dropping out of battery and it would still drop the hammer. Check the function of the disconnector before you buy.