Even rifles and shotguns have failed to stop bad guys on occasion. That being the case, ANY handgun, regardless of caliber, can and will fail. Handguns are a compromise. They are hole punchers, nothing more. They do not have the velocity, not even the 454 Casull (note the correct spelling), which I own and use to hunt big game with, to guarantee an instant drop.
Every deer season there are instances where 150 pound deer are hit perfectly by guys using centerfire rifles like the 308 and 30-06. However, even though these deer are hit in the vitals with rifles that make FAR more power than even the 454, still can run 100 yards or more before dying. That being the case, do you really think a .45acp is a "stopper" or stops any better than a good 9mm JHP? Handgun cartridges are all too close in power (yes, again, even the 454) to instantly drop a human in their tracts, except for a CNS (central nervous shot). Again, I urge you guys to read the link from ammolab.com. It's a FAQ section that deals with myths like "stopping power", etc.
The following is an excerpt from an article that explains why firearms fail, even the big ones, at times when trying to stop a determined attacker. Source is here.
This is a true story that occured in NJ.
The bottomline is as long as there is oxygen in the brain, which there is for up to 15 seconds after someone has been shot even with a direct bullet through the heart, he or she will continue to live. 15 seconds is a very long time when that person is shooting at you. The fact is, pistol calibers are piss-poor at incapacitating humans. A .45 is down-right puny when compared to a 1 ounce, .72 caliber 12 gauge slug that the above mention bad guy took to his chest. If he didn't stop on the spot by the slug, do you really think a .45 caliber pistol would have stopped him?
Can't say it enough, carry what you shoot best and pray you never have to use it.
