Why the Forty for defense?

an editorial by Mark Freburg

I received the following question about the .40S&W cartridge recently and thought I'd publish my reply. 

"I'm curious.  You've probably discussed this before, but why the interest in .40? I have one firearm in .40 S&W.  I've kind of struggled with accumulating more in that caliber.  I tend to favor the 9mm or the 45 ACP.  Both for different reasons.  I love the economics and availability of the 9mm and the hard-hitting power of the .45.   I've always looked at the .40 as a compromise.  Higher velocity than the .45 but greater mass than the 9mm.  Anyway, the LE community sure seems to like it." 

I'm glad you asked that question because the topic interests me, plus you force me to analyze this a bit. 

I had some interest in the 10mm so I was interested when the .40 came out in 1990. I waited what seemed like a long time to try it out--I bought an EAA Witness (CZ75 clone) in 1994. At that time accuracy wasn't that great with factory ammo, but once again the gun press was too worried about target accuracy and not enough about combat accuracy--and there the .40 was fine. Since then, the .40 now is as capable on targets as most any caliber in similar loadings. By that I mean there are still unique target loads for the .45ACP especially that will blow away anything else--but we have to remember that those .45 target loads would suck for self-defense. So it pays to compare apples to apples. 

Since the Witness, which I let go, I have had a Smith & Wesson 4053, a Browning Hi-Power, a SIG P239, two Glock 23s, a Glock 22, a Glock 24, a Glock 35, and Glock 27. I still have the last seven forties. The Smith was a good gun in every way except for its trigger--the long DAO just wasn't my cup of tea. So it's gone too.  The Hi-Power was also a good gun, but my interests changed.  I list these guns just to show I've played with a variety of action types, and so my comments on the cartridge are about the cartridge itself, not the guns. 

Most savvy folks who have been in the gun game for a long time did or do consider the .40S&W a compromise round. The early guns and ammo solidified this impression. Consider this little table I made.  One can see how the .40S&W came right smack in between the other two rounds when it first appeared.

Those figures don't tell the story however.  While the above info is based on averages, neither the 9mmP nor the .45ACP have changed much.  The .40S&W has changed a lot.  It started as a 180gr bullet at 950fps which is quite similar to a 185gr .45ACP, although the .40 has a better ballistic coefficient.  Does that matter at close range?  Oh, probably not, but having longer range capability never hurts. 
 
But since that original load, the .40S&W also comes in 165gr, 150-155gr, and 135gr loads.  The 135s run 1325fps to 1350fps, with the middle loads in between the two.  So if someone wants a light bullet at high velocity (like the incredibly effective .357 Magnum, he can have a load that has approximately the same energy as the .357--well over 500 foot pounds.  This exceeds the 9mmP, which usually has about 325 to 350 foot pounds of energy in common loads, yet the .40S&W is available in most of the same guns as the 9mmP.  Where the 9mm shines IMO is in the super small hideout or backup guns, because 9mm recoil is lighter than the .40--and in the tiny guns it really matters.
 
The average .45ACP like the Federal 230gr Hydra-Shok load achieves around 400 foot ponds of energy, about the same as the 180gr .40.  Clearly there is no major power advantage with the .45 auto.  To those who feel momentum is the critical aspect of stopping ability, I'll have to suggest you do the research yourself as those figures are not readily available compared to energy figures--which should tell you something about the industry's opinion on the subject.  (You'll need a ballistic pendulum to test it yourself.)
 
As to bullet diameter, I don't think it means a lot.  35, 40, or 45.  Bigger is better all else being equal, but when is everything else equal?  I like the .40 because I can have a high capacity pistol without sacrificing a comfortable grip.  Nowhere is there a better example of this than when comparing the Glock 21 .45ACP with the Glock 22 .40S&W. The 22 fits most people well, the 21 does not.*  They are making progress in down-sizing .45 autos--Glock had to go to a new, shorter cartridge with their .45GAP, but it does have .45ACP ballistics.  Springfield and Taurus have plastic pistols in .45ACP that improve on the Glock 21 but they probably still won't fit all hands as well as most 9mm/.40S&W frames--which are identical in most cases.  Para offers wide-stack 1911-based pistols, but those are not a particularly good universal fit.  I think ultimately one can have a single stack .45ACP that fits them well--1911, SIG P220, Ruger, etc.--or they can have a double stack in their choice of 9mm or .40S&W.  As long as the guns don't get too small the .40 wins the power battle there.
 
Is mag capacity important?  It is to the police, who have overwhelmingly turned to the .40S&W.  The private citizen generally has much more leeway in choosing a defensive piece.  Most of us live safe and sane lives and don't deliberately go into harm's way.  Our own personal ideas about this topic will govern our choice of gun and caliber. 
 
I tend to be one who believes that if you feel the need to have a gun, you should carry something big enough to handle easily and shoot accurately, of enough power to get the job done as well as a handgun can, and with enough ammo that if, God forbid, we have to shoot in self-defense, we will not run out.  When it comes to self-defense guns I am a belt and suspenders guy.  I even carry spare ammo.  OTOH I rarely practice speedloading anymore and probably fall back on my higher capacity guns.
 
My normal carry is a .40S&W.  I frequently carry a .45 and have even carried my 10mm a few times.  For quick, "safe" milk-and-bread runs, I sometimes turn to a tiny 9mm.
 
The .40S&W is a compromise still in the sense that it falls in between the 9mm and .45ACP.  It will always be so.   Yet there are more loads and more variety of ammo types in .40S&W than anything else now.  There are also more guns.  The 9mm kept up for a long time but note that S&W's new M&P Auto came out first in .40.  That is telling.  If the .40 is a compromise, it is a very good compromise indeed. (3 April 06)
 
* Since this was written Glock came out with the better-fitting Short Frame version of the Glock 21.  (updated 15 March 08)