Whoever told you bullets tumble out of a P3AT had butterflies in his head. Out of hundreds of tests with many, many different brands of ammo, I've never had a shot "keyhole" on the target with a P3AT. (There was a case reported with defective reloads. Not with good ammo.)
Now, there is a 380 pistol that does produce "keyholing" and that's the SeeCamp LWS 380. The short, 2 inch barrel is not long enough to get the bullet spinning and stabilized. Some people think this is good. But that's why I do not recommend buying a pistol with a barrel shorter than 2.5".
Also, the P3AT produces good velocity with most JHP ammo, both in gelatin per Goldenloki's work and in wetpack tests. There are exceptions, mostly due to a poor bullet design, like some MagTech stuff. Or with defective ammo from the factory, which can happen rarely.
Clik on my sig line WWW thing for access to dozens of 380 test results.
og