[Armedanddangerous]

These rules will serve you well.

1. shot placement
2. Shot placement
3. In in the words of Massad Ayoob..air rushing in, and blood rushing out. The secret is to choose the bullet that causes the most bleeding in the target in the shortest amount of time. THAT is what causes the goblin to lose interest in interacting with you and persuades he or she to fall down or go away and fall down.

In my Glock 26, I choose Cor-Bon 115 gr +p+
In my 45 acp Kimber Gold Match, I have a case of Remington 185 Gr +p+ ammunition, that I use sparingly, because I don't think they make it any more.

[epow]

Up until recent years, the general concensus among people who shoot other people in their line of work seemed to be that either the .45acp or the .357 magnum were the rounds to count on when your life is at stake. OTOH, the .40S&W is now the standard police round in the US, and there must be a good reason for that too. The newer .357 SIG is also used by some departments. I have never fired a .40 caliber pistol of any kind myself, but I have friends who believe they're the best thing to come along since smokeless powder.

I wouldn't hesitate to choose a 9mm, or even a .38 with good ammunition, if I were limited to a medium caliber handgun. But since I'm not, I practice regularly with both a .45acp 1911 pistol and a model 66 .357 magnum revolver. It's almost impossible to conceal either of those guns in hot weather clothing, so I admit to carrying a small .38 revolver, or at times an even smaller .380 pistol in summer. My theory is that in the unlikely event that a life threatening confrontation occurs, any gun is better than no gun. So even if I were for some reason restricted to only a .22 or .25 caliber pistol, I would make it a point to have it close at hand whenever possible.

[Hinoki Cypress]

I carry a full 5" frame Kimber .45cal ACP with Corbon +P 165gr JHP hollow-points (1250fps/ 573ftlbs) and also use Sellier & Belloit 230gr as a practice round. Since I wear my shirttail out, concealed carry isn't a problem even in the summer. I still carry my Glock 32/.357sig and use Corbon 165gr for that too, in the appropriate caliber.

That said, and a bit off-topic, I just bought a .50cal Beowulf - http://www.alexanderarms.com/beowulf.html - and I can guarrantee anyone that it'll drop anyone with one shot. Go to the ammo page and see the 325gr and 400gr loads. Their motto is, "If you are going to make a hole, make it as big as possible" is correct. A bit *too big to carry concealed*, though. Blew a piece of 12" x 12" oak lumber into teeny-tiny splinters, though. Awesome stopping power.

[5Madman2]

All the comments you've gotten so far are valid. There is no magic bullet, althought the 45 aficianados will sometimes lead you to believe it is (I avidly shoot 45 ACP). You need to look at your overall situation. How big a gun can you carry based on concealment needs and how well can you shoot the weapons you have. Mass and energy transfer are true, but they mean nothing if you can't hit with what you shoot so shot placement is critcal too. A target hit in a vital area with a .380/.32/9mm will suffer more energy transfer that a target missed with a .44 magnum.

Find a weapon you are comfortable with, get good quality factory hollow point ammunition (Speer Gold Dot, Remington Golden Saber, Federal Hydra Shok, Winchester SXT)to carry in it. Get some decent target ammo and shoot. A lot. My solution to the shooting a lot is a Dillon 550 progressive re-loader and once a week on the range with my duty weapon and my fun guns

The right gun to have in a crappy situation is the one you've got on you. Make sure you know how to work it and hit the target. Good Luck

[Mulder]

Shot placement is the most important factor.

Kinetic energy is the next most important.

Other folks have complied numbers on the kinetic energy of rounds. 45 caliber and 357SIG are at the top of the list of practical calibers. .40 is close and 9mm is lower. There is a big gap between 9mm and .380.

For that reason, I'd be uncomfortable depending on anything less than 9mm.

[SauronOfMordor]

Therefore, is it possible that even with a "smaller" caliber such as .22 or .380, I can compensate by having a higher velocity round? In other words, do different types of ammunition vary that greatly in speed as to affect stopping ability?

A 55 grain .223 will have significantly more stopping power than a 150 grain .38, due to higher velocity, and thus higher kinetic energy.

The "stopping power" of a round is dependent on how much kinetic energy can be applied to damaging tissue and causing rapid blood loss, which depends on how much energy is in the round, and how much of that energy is actually expended in the target (a round which makes a neat tiny hole and expends most of its energy in the wall beyond the target doesn't do you that much good.

Big, deep holes are better than small or shallow holes

Depending on the target, a .22 may stop one aggressor, while another (for example, hyped up on PCP) may require an RPG splattering body parts over the landscape to stop.

One final note: a .22 in the hand beats a .44 magnum left home in the closet. The ideal carry gun is the one light enough to be carried habitually, while having enough power to take down an average attacker. You may be best served by having two carry guns: a small light one for times when concealability is most important, and a .45 for those times when you need to be going thru nasty parts of town at night

[Shooter 2.5]

There are diffent ammunition manufacturers that make different types of ammo for the same gun.

Let's say you have that Walther .380 and you decide to practice. You can go to Wal-mart and pick up some inexpensive ammuntion that has a standard Round nosed Jacketed bullet on a standard load of powder. The powder would give a medium velocity and you could practice all day with it.

The same manufacturer could also design a bullet that could open up to a larger diameter and increase the powder charge for a higher velocity and it would still be safe to use. The price of the ammunition would be higher too.

Include a half dozen manufacturers making different cartridges for different applications and you could see a wide range of ammunition that can be used in the same pistol.

[tdadams]

I think a lot of people are confused by stopping power and lethality. I see a lot of people who seem to use them interchangably.

Almost any size round can be lethal if used right. As someone else posted, the AR-15 (an excellent gun) uses a .223 round and it is a highly lethal weapon. However, if you shoot someone with a .22 short round from a short barrel pistol, well you might as well beat them over the head with the pistol. It will probably be more effective.

A bigger round, like a .44 magnum, a .45 ACP, or a .50 caliber will almost always stop someone dead in their tracks. A smaller, high velocity round like a 9mm can go straight through someone without them even realizing they've been shot (for a while anyway).

But I also subscribe to the school of thought that says I'd rather carry a .25 than nothing at all.

[TLI]

Stopping power?
OK just remember this when everyone is going on about velocity + mass >>> energy = some number and so on....

A 9mm MIGHT EXPAND,
A .45 WILL NOT SHRINK.

Think Glock 21.

[Jim Noble]

Hitting the target is #1.

[rockfish59]

Well, I heard the 'Mob' uses .22's to the back of the head.

My personal .357 handload is a 110 grain hollow point with 23 grains of 296 ball powder.
At 1,600 fps it should stop something!

[archy]

What are the most important factors in determining "stopping power"?

First most important? Availability. The first rule of surviving a gunfight is to have one with you when it happens. And sometimes, just your having one will keep your problems away, just as having an umbrella seems to make it less likekly that you'll be caught in the rain, or the presence of having a first aid kit seems to lessen the odds of the need for one. Of course if an umberella or first-aid supplies are needed, that need isn't as disasterous if the required equipment is at hand and familiar.

After that comes reliability. Neither power nor accuracy will do you any good if anything prevents your most critical first shot from happening, and a stoppage of followup shots can be just as unfortunate if multiple or particularly enthusiastic opponents are involved, with firearms themselves or without.

Then it's accuracy. You *might* get lucky and scare off an inexperienced or amateur burglar or holdup rookie, but you'll more likely encounter some experienced ex-con who'll figure the only out of the mess he's in will be to kill you. Nothing personal. In that case, you'll have to hit him to stop him, or at least slow him down enough that you can both make your escape. And again, if you're facing multiple assailants, you won't want to be wasting ammunition.

After that you can begin to concern yourself with bullet diameters and mechanical systems of operation. But you can learn the principles with inferior equipment, and improve on your gear once you've at least got a rudimentary grasp of the fundamentals. I'd far rather spend $200 for a fair handgun and $300 for ammunition with which to practice, than $500 for something newer and more state-of-the-art with only a box or two of ammo with which to run through it. Handguns that can use inexpensive surplus ammo are a good dweal in this regard, as are those for which reloaded ammunition can be arranged or obtained.

-archy-/-

[George Smiley]

Hunt down the "rec.guns FAQ".

Search using that exact phrase.

There's an entire section devoted to ammunition and a subsection devoted to self-defense ammunition.

[Trooper512]

Stopping power: once upon a time there was not much question about this. The Army used big (and fast) bullets (45 ACP,, 30-06, 308). The frontier shooters (big N.A. game) used big (slower) bullets -- 45 Colt, 45-70, 30-30. Experience taught them that a big bullet was needed to knock down a big target. When they started messing with full auto rifles, the problem became how to carry around all the ammo they can process. (It took 2 guys to carry a BAR and feed it) So they opted for little cartridges. I do not like the 223, but it is adequate for man killing. The 9 mm is worthless (North Hollywood proved it). Skip the engineering tech notes and get a large caliber (pistol .357 mag, .40, .44 Mag or 45 ACP). If you want to shoot through car doors and windows take a magnum. (Rifles: 30-30, 308 or 30-06; Grizzly 300WM). Bullet -- flat nosed lead (SWC) knocks down, jacketed penetrates, JHP does both. Magnums prefer jacketed or JHP. If you need more firepower than this you have a really special problem and need some special planning.

[EdReform]

BTTT to find later

[Durus]

First most important? Availability... After that comes reliability... Then it's accuracy... After that you can begin to concern yourself with bullet diameters and mechanical systems of operation. (Archy)

That couldn't have been better said. There is way to much hype concerning ammo/caliber selection and Archy, in his wisdom, has cut to the chase. Anything 9mm or greater is a sufficient round if you have met the criteria above.

[Little Ray]

There is no such thing as "stopping power." Physics dictates that every action has an equal an opposite reaction. If a bullet could knock down a target human, then the firearm that launched it would knock down or injure its user.

The reality is "wound channel size." Basically this how big a hole the projectile makes in the person. Bigger bullets make bigger channels; since bullets keyhole ("tumble") when they enter flesh, bullet length can also affect the wound channel size. Finally, the velocity determines how deep the bullet penetrates (and may otherwise widen the wound channel). These are the basic factors governing the lethality of ammo.
There are other factors such hollow points (expands to a larger diameter), jackets, etc.

In the end though, the real "stopping power" is shot placement. What you really want is a fire arm and ammo you are comfortable shooting, then you want to practice a lot. Tape over the sights, too. According to some folks, you might not be able to use them in a real gunfight.