The .45 ACP was the only round specifically developed for the military to stop a man dead in his tracks. The weight, size, and speed were taken into account to do just that and in my opinion is still the best man stopper out there. They sought this stopping power during the Banana Wars, tribsman in the jungles would attack them high on some type of drug and the old .38's just would not stop them, hince the .45 was born. The 9mm is the same diameter as the .38 with just a little more umph behind it, that proves to me it's ability, of course that was with hardball ammo, the stuff out there does help the 9mm (9x19) out a little.