Well I'll play the advocate and comment on why I choose 9mm over .40 and .45. I'll start by undermining my own choice by saying I think they all are good choices and nothing I am about to say can change that. But...
Starting with ballistics, 9mm, .40, .357 sig, .45 ACP, and .45 GAP are all gel and street proven. Modern bullet designs have closed the gap dramatically in terminal performance, although one may need to be a bit more selective with 9mm ammo for self-defense, but that's easy these days, Federal Hydra Shok, Remmington Golden Sabre, Speer Gold Dots, Corbon, etc.
It has been debated endlessly which caliber works the best but all have proven to work well and fail miserably - they are handgun rounds - they are anemic. Plus, all "experts" agree that shot placement is far more significant than the difference between a 9mm and .45 cal. size. I personally saw a police video of a man shooting a woman three times in the upper torso with a .45 ACP. Not only did the woman not go down, she ran around a car yelling, "He's shooting me!"
Ostensibly the 9mm has a slight capacity advantage over a .40 cal, but essentially nearly insignificant.
This will step on some toes here, I don't mean to but, I personally believe there is a signifcant advantage in capacity "in the gun". I know, I know the average gunfight and all that, but I prefer 15 to 18 9mms over 8 or even 9 .45s. This is where the "spray and pray" and the "you must plan to miss a lot" incantations usually begin. Well, if I'm in a gunfight, you can believe I'll be praying. I shoot about 200 rounds a week, so I hope I won't be spraying. And, I don't plan to miss a lot but, I do plan to shoot a lot, at least until the gunfight is over.
It seems unrealistic to think that we will always have the opportunity to do the two to the COM and one to the head when we're moving, the BG(s) is moving AND shooting, so I'd think it'd be pretty good planning to figure we may miss some. I believe I am correct in crediting P45Carry with posting the concept of suppressive fire as a tool of excape. I concur. I can do that better with more rounds.
I have changed my mind recently about speed reloading in a gunfight. I no longer think that's a good thing to count on. Oh, I still practice speed reloads, I just now believe that in a gunfight, if the rounds are not in the gun, they are very unlikely to become involved in the gunfight. In the stress of a gunfight, it will take 2 - 3 seconds to speed reload if we don't muff it. I know, we can do it in 1 second in the "match" with all that match pressure, but how many rounds are incoming at a match?
I have had the unfortunate experience of hearing, without muffs, a .40 cal and a 9mm discharged in an enclosed room that would typify a room in a home. I can tell you the difference between a .40 and a 9mm muzzle blast is tremendous! The .40 cal. Corbon blast was painful, my ears rang and my hearing was diminished for quite a while. Many years later, this was repeated with a Gold Dot 9mm. Because I was dumb enough to do it that's why. I was surprised that I didn't experience the pain and I don't remember the ringing as prominent. Also, I could hear surprisingly well. What's this got to do with anything? Well, if you have to defend yourself in your home, you have to deal with the muzzle blast. I know, under stress we don't hear the muzzle blast anyway. The problem is, not only will we not hear the muzzle blast, if the muzzle blast is very loud, and a .40 is, we probably won't hear so good afterwards - that's not good.
I know none of us are recoil sensitive and we can handle the recoil of a 230 gn .45 just as well as a 115 - 124 gn 9mm. Well, unless you have some extenuating issues like weaker wrists, etc. the dreaded arthritis, or you're a woman with a smaller frame, or you don't want to compete with a .40 or .45 against a comparably talented guy who shoots 9mm. Or, you still believe in the laws of physics. So I guess there's no sense discussing recoil.
I shoot a lot, as I mentioned, about 200 rounds a week; that's not counting about 1200 rounds at some training school nearly every summer. At Walmart, I can buy 100 rounds of 9mm for $11.34, 100 rounds of .40 cal. for $15.97, and 100 rounds of .45 ACP for $19.97. Maybe that doesn't sound so significant, but if you consider I'll shoot about 11,000 rounds a year, that's $1247 for 9mm or $1756 for the same rounds in .40 cal. That's a yearly savings of $509.70. The savings would represent potentially, buying a gun a year just on the savings.
But, if you don't shoot much, first shame on you, then there's very little economics involved. But some don't shoot much because it costs too much. To offset the costs, some practice with 9mm and carry .40 or .45, but many, myself included, tend to think that's not the best approach.
For self-defense ammo, the economics are almost insignificant - it's all expensive.
So for the 9mm, effective terminal ballistics with modern bullet designs, high round count in the gun, lower muzzle blast, less recoil, and more economical to shoot.
Euc, see what you've done, to quote a respected friend, "I outta be shot with both calibers for making a thread like this..." :bigsmile: