It's worth noting that no rifle (even if you were insane enough to try using a 20mm anti-materiel one) can guarantee a one shot stop on a man sized target by firepower alone.
Physiologically the only way to get an instant stop with a firearm is to sever the upper spine or brain stem, and that is something that is entirely dependent on shot placement. A .22 is as good as 20 mm provided you hit.
True. However, for non-CNS hits, rifles do offer more incapacitation potential than handguns. One may quibble about whether pressure wave and cavitation effects are significant contributors to incapacitation with handgun calibers, but with rifle calibers using expanding ammunition, there is no question.
Heart/lung shots are reliably lethal in a short period with pretty much any modern firearm bigger than a .22 with suitable ammunition. Depending on shot placement and timing the short period ranges from several seconds to several minutes. I should explain the timing comment; a strong impact on the heart at the right point in the beat cycle can cause instant cardiac arrest and is the mechanic resposible for 'instant' drops in chest shots in combat or hunting situations, it cannot be relied upon to happen though.
Again, quite true. However, if you compare a .22LR bullet that makes a quarter-inch hole in the ventricles, and a high-energy rifle bullet that produces a temporary cavity larger than the heart as it passes through the ventricles, there is no comparison. They may both be comparably lethal, but the latter will incapacitate more quickly.
The truth is that no matter what firearm you use for personal defense under practical circumstances a determined attacker armed with a firearm should be assumed to be able to survive long enough to target you and fire one or more shots even after you have hit them. The thing to count on is not your firepower but the probability that the average attacker is likely to find, "hit the wall you are facing," to be a fairly challenging feat of marksmanship.
Which is why, if you are facing an armed attacker, it would be foolish to fire once or twice, stop shooting, and hope the attacker drops before he decides to shoot back. Such a situation, while rare, would be precisely the type of situation in which one would not want to be limited to a paramecium-sized 5-round magazine.
Personally I wouldn't recommend a firearm for home defense in most situations in first world countries. A can of mace, a tazer or two, a high intensity flashlight, a cell phone, and some zip ties or handcuffs are probably a better toolkit if you take the time to learn how to use them. Designed for short range, rapid incapacitation, non-lethal if used against you, and you're not in legal trouble if you use them and they work.
It is extremely inadvisable to use any defensive spray indoors as it will incapacitate you as well. Also, mace is of
very questionable efficacy. Also, it is possible for an enraged attacker to fight after being sprayed with OC, even if he is blinded, and an enraged blinded man in close quarters with a knife would still be a fearsome opponent.
A Taser functions like a one- or two-shot handgun with rudimentary sights, a 21-foot range, and little reload capability. If you are questioning the ability of the average person under stress to effectively hit an attacker with a 15-round handgun, the Taser would be harder still. You also can't afford to shoot a Taser regularly for proficiency.
IMO, the Taser's niche is as a bridge weapon in nonlethal altercations that do not rise to the level of "imminent danger of death or serious bodily harm", or in law enforcement use when backed up by another officer with a real gun.
Also if the silhoutte of the presumed evil dangerous intruder turns out to belong to someone you know and like it's a heck of a lot easier to turn off the tazer and rinse their face off than it is to do a bit of on the spot trauma surgery.
That is why I have a light on my primary defensive firearm. Shooting at unidentified things in the dark, whether with a firearm or a Taser, is exceedingly unwise.
If you actually want to be safer though, any firearm sufficiently accessable for personal defense is a bad choice if you come at it from a safety engineering/public health point of view. The probable cost of a lethal accidental discharge is far greater than the probable benefit of saving a life by shooting an attacker.
Lethal accidental discharges are FAR less common than successful defensive uses, by two to four orders of magnitude depending on the population under study and how defensive uses are quantified. I would also point out that the vast majority of successful defensive uses do not involve shots fired, and the majority of successful defenses involving shots fired do not result in the death of the attacker.
My own father had a "save" with a lawfully carried pistol at a remote river access point in the Croatan National Forest, many years ago. His would-be attackers saw the gun, backed off, and left.
If you are not at high risk of suicide, and do not belong to a criminal household (as an inordinate percentage of accidental shootings involve criminals and their families), firearms do have a very favorable risk-benefit ratio, even more so if you take the time to become fully competent with them.
If you want to BE safer it's critical to understand the difference between things that are merely scary ( sharks, rattlesnakes, international terroists) and things that are genuinely dangerous ( the teenager down the street learning how to drive, going boating after a few beers, reroofing the house without fall protection).
Quite so. And a competent adult thoughtfully keeping a loaded firearm accessible for defensive purposes, but secured from unauthorized access, is not in the "dangerous" category by any rational measure.