The only ammo I know of that is not recommended for use in the P3-AT is MagSafe.
There is no SAAMI standard for +P in .380 ACP; either it is marketing fluff, or they are loaded above the maximum pressure for .380 ACP, which makes them outside the standard completely. I suspect the former.
i have heard from several reliable sources that their claimed velocities are real and reproducible, which would imply that in their case, the p+ notation is more than just marketing. ive seen many posts on this board from users shooting them in their p3ats. per keltecs advice p+ ammo can be used, but in moderation.
Some of the ammo I used this PM to check function of my newly returned gun was some Buffalo Bore +P 100gr. There is a difference! Bout tore the gun from my hand. (J.K. ;D) Seemed to be harder to hit the target on the second round and the slap was more pronounced, thinking about using the Buffalo for the 1st round and CorBon DX for the rest in the mag.
(Or maybe the other way around, kinda like a 'hail mary' play)
If you want it to be a 9mm, you need to trade it for a 9mm.
With that said, the .380 is perfectly capable of putting a DGs di ck in the dirt with standard ammo.
All you have to do is hit COM and keep hitting COM until he falls down, or decides it hurts to much to stand there and let you shoot him.
With that said, practice with ammo you can control, and Buffalo Bore isn't necessary, or necessarily desirable.
A couple of weeks ago I purchased some MagTech Gaurdian Gold +P JHP for my P3AT by accident. I did a little research and couldn't really find any thing saying it was ok to shoot it through the P3AT. So I called Kel-Tec and they said not to shoot +P through the P3AT. On their website is says it is ok to shoot +P in the P11 and PF9 but not all the time. Hope this helps.
I've shot the BB JHP and HC in my P3at. I know it's hard to tell the velocity based on recoil but I found it to have more recoil than standard FMJ. It was also more difficult to shoot well compared to DPX or Critical defense. I also question the reliability in my P3, I don't remember any FTF. It just feels like a little too much for the P3.
Well I just had to make a run to the Sprint store to get a couple of our phones fixed and while I was out I decided to stop by a couple of places to see what the ammo situation looked like.
Either I showed up at just the right time or else the ammo shortage is fading away. Both places had every shelf full of every caliber!
So I picked up some 380 ball ammo and a couple of boxes of JHP's in 380. The JHP's were Critical Defense and Remington's yellow and green box (read: expensive ) JHP's.