Hello all. I'll bet that part of the reason that we are all involved in this "stopping power" discussion is that the choice of defensive ammunition is something we CAN control unlike many of a firefight's parameters. I'm "on record" as stating that 9mm with high performance loads is my favorite all around caliber and one I've used confidently for self-protection for years as both a police officer and private citizen. As many have said, "There's no free lunch," in this "stopping power" aspect. Usually, this has been in reference to recoil and weight/size of weapons. I think it should apply to yet another aspect, placement. I do believe that a .38 is "better" than a .22, but only if they are both properly placed; a perfect hit with a .22 will be better than a graze with the .38. With certain loads, I've little doubt that forties and .45ACPs, etc are "better" than a hot 9mm, but I don't think that the difference is as great as might have been believed in the past. Example: A police officer under my command took a (low) torso hit with a 180 gr JHP in .40 S&W. He was seriously injured, lost a kidney, nearly died, but didn't even know he'd been shot until officers having seen him shot advised him to sit down while they summoned medical attention. (I don't honestly remember the ammunition make, but did see the recovered bullet which was mushroomed and partially fragmented.) Another officer who'd worked for me was forced to shoot a felon while in a life-and-death struggle over the officer's weapon. The felon was shot squarely in the heart and dropped instantly, apparently dead on the scene. (The load was +P Federal 124 gr HydraShok.) It, too, expanded and showed some fragmentation. The difference was shot placement in my opinion. I do agree that a 9mm with proper loads is the lower limit for a "serious" defensive handgun, but recall yet another case in which a citizen being chased by a dude with a knife, fired one shot from his Raven .25, killing the dude with a heart shot. The load was the Winchester FMJ load that has virtually no "stopping power." This bullet did not expand and made but a tiny wound to the eye. Placement did the trick.
I truly believe that the nine with its best loads (whatever they are) is superior to some larger calibers with certain loads, but that heavier calibers such as forty and forty-five
with their better or best loads will exceed the nine. Much earlier in my career, 3 officers were involved in a firefight with a fleeing suspect who was shot with a .38 Spec JHP, a .357 Magnum 158 gr JHP, and a .45 ACP 230 gr Norma JHP. All were torso hits, but not centered. This suspect outran the officers and was found nearly dead from loss of blood in a garage! This was over 20 years ago and neither of the two recovered JHPs expanded at all. The .357 bullet was not recovered as it'd passed all the way through the suspect. 9mm, .40, and .45 high performance loads are sufficient rounds with placement and all are deficient without it.
Best to all.