To predict the future we only have example from the past that may repeat themselves in a similar way in our presence and may call for us to defend ourselves with a firearm.
Virginia Tech recent shooting
VT a few years back
Flash Mob robberies (did these really happen the way they were reported?)
Ok, what are the attributes of these events? Well in some, it is a single, semi-determined shooter with a group of targets they are attempting to murder. Low capacity pistols and good shooting and a 5 shot snubbie would have been all you'd need in a Luby or VT situation. So obviously the "you want that ammo capacity! 18+1 and 2 reload mags are a START!" argument doesn't apply there.
Another is a ambush. Even the most alert and trained person can be bushwhacked. Like that officer in VT the other week. It can happen. And it would suck if it happened to you. Again, if you had a .22 derringer or a Thompson sub machine gun with 4 extra drums with you, it isn't going to matter. Ammo cap is irrelevent in that scenario, too.
The others is group of assailants, going after a single good target or a group of targets. It doesn't really matter which if you fall inside the Venn circle as 'target' (like a flash mob) and are alone or are one of very many (like in Mumbai)
I'm not a cop. I'm not an infantryman. Chances are if you are CCWing you are not either. There is no duty to 'get' the bad guy, save the day, rescue the kitten, put out the fire in the orphanage, and take on evil single handedly. While it is often very nice when such a heroic circumstance occurs that is not your responsibility. You carry CCW for defense, not offense. Your pistol is for getting your butt out of a jam that has been initiated by someone else. Regroup. Get a rifle if the situation warrants going on offense. But offense is also beyond the scope of this post.
The hypothetical circumstance a high capacity magazine address is a group of armed or unarmed assailant targetting you alone or you and a bunch of other people, but you are the only one that thought to tote a pistol.
Let's stipulate first, right off, if a group of armed assailants wants you dead your future outlook is not so good. Your chances aren't GREAT with a group of unarmed assailants either, but obviously better.
So what do you have when going against a group? The group might not be expecting you to be armed. The introduction of ANY firearm, regardless of capacity, might be the only edge you need. You'd alter THEIR decision making process in many circumstances. In that case a capacity of "3" may be all the bullets you need. Only "1" as long as the bad guys don't know that that is all you have. 20 unarmed assailants and one of them takes 2 rounds from your 5 shot snubbie? You can only shoot about 3 more, or so at that point. 16 assailants will be unscathed! You're doomed! Except none of ad guys wants to be numbers 17 18 and 19. Many cases, they will run away.
The same COULD apply to AK wielding terrists at the mall. 2 shots from a snubbie and they start to wonder, "yeah, that guy has just snubbie, but this is a big mall and who knows how many more guys like him there are... Better withdrawal, regroup, and rethink this."
Ok, no really support yet for high capacity magazines yet.
Now for the really dark scenarios. You are against a group of unarmed hoodlums (let's dispense with the mall terrists at this point, you're gonna have to be lucky AND a good shot, AND fleet of foot against that kind of evil doers...) and the unarmed hoodlums aren't dissuaded by the surprise presesence of a pistol in your hand, aren't detterred by the VERY loud bangs of a round or two, and they don't care that one of their group just had his gray matter introduced
This is the meat of the high cap argument. THis is the snubbie carrier's Kobiashi Maru, the supposedly unwinnable scenario. This is where T-Bolt thinks, "Man I wish I had Glock 17, instead, right now." And the high cap people win the argument and everyone get's a double stack carry piece, right?
Not necessarily. The scenarios can ALL be ratcheted up. You can add more adversaries to the mix so that the Glock guy with 55 9mm rounds ready to go says, "Gee, I really wish I had my AR, and a buncha friends with ARs, today, and a few hunder 30 round mags. This is a hairy situation!"
The only REAL histoical scenario where the high cap mag is vital is the unarmed flash mob assault. And those aren't prevalent as yet. It's up there with "killed by meteor" chances. Some might armor their roof. My risk assessment is... The advanatage a high cap 9mm gives me is not so big a jump as to justify the extra hassle and inconvenience.
With those 18+1 and 2 spare magazines... Your gunfight will be over before you get one quarter of the way through that first magazine in non meteor hitting your head probability cases.
When carrying a semi... it is worth the hassle and inconvenience, to me, to have a spare magazine because of the point of failure inherent in a single magazine. But those 2 magazines could carry 5 rounds, for all I care.
If a gun fight comes to me, I hope to have the biggest quantum leap in requirements. A gun. "The important thing about a gunfight is to have a gun." That improvement from nothing to something is a much bigger jump than 5 rounds to 55 rounds. That gun, nowadays, is a 5 round snubbie. One day will be a 8 round 1911. Even that 5 rounder is rare, of course, because of my state of residence. But that's an old familiar story round here.
Ooops. Tam summed up my post much more succinctly in a comment:
"GENERALIZED RANT TO THE ENTIRE GUNTERNET:
Here’s a secret: .38 Spl +P 158gr LSWCHP will reliably expand to .6″ and shoot purt near clean through a man no matter which angle you shoot him from. Anything beyond that is just whistling past the graveyard.
I carry a 1911 because it works, and because I shoot it the best. I carry it in .45 because that’s the caliber that is most reliable in the gun.
Caliber itself is bullshit. Capacity is bullshit. All this “mine holds 18″ rounds stuff is just as much pointless wanking as the “Europellet” nonsense and you all know it as well as I do. This isn’t Mogadishu, and if it were, I’d be carrying a fucking carbine anyway.
Carry a gun that works. Carry the gun you trust and that you shoot best. Period fucking dot.
Jesus. Wept. But I have so lost all my tolerance for the silly gun forum/gun shoppe counter “Glunk” and “Europellet” and so forth pointless chest-beating about make, model, and caliber… Shouldn’t you people be off training someplace?"
I'm carrying the set up that doesn't pull my pants down. With the pistol I reliably hit stuff with. With a single set of reloads for the just in case factor. When the Wildings or Zombies get prevalent I'm carrying the M14 and bringing friends. If my JOB becomes chasing bad guys, that snubbie I'd prefer to carry might be innappropriate. Until then.]
[Update 2: No one ever says. "All I had was the one mag of for my 1911, and it wasn't enough" outside a battlefield, have you noticed? Cops run out of revolver bullets, and 9mm, but never complain that they didn't have enough for the 1911. Is it because the 1911 cops panic less and miss less because they train more?]
[Update 3: From here, "If you carry, be prepared to shoot. Some folks carry around a pistol like a talisman to ward off evil. They figure if they ever need to draw, they will not need to shoot. That thinking may get you killed. You might NOT have to shoot, which is fine, but don’t assume that to be the default." Oh, it is most definitely not a talisman.]