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40 vs 9mm

9mm vs 40: This Time It's Personal

If there's one thing that's been argued to death, it's 40 vs 9mm. However, people love to talk about it anyway so we're going to hash it out one more time!

Both of these rounds are intermediate, in that they aren't too powerful nor are they too big. Each has their dedicated fans. Both are definitely proven self-defense rounds and - along with .45 - are among the most popular carry rounds out there.

Which is better? Well, both have their strong points but ultimately, it's really down to which one you shoot better or prefer. The reality is that neither of these bullets are barnburners and everyone needs to calm down. You have to get into the big magnums before any handgun round becomes anything to write home about.

40 vs 9mm: The Smallest Big Bullet There Is

40 vs 9mm

For those that missed the story, there's a reason why the whole 40 vs 9mm debate favored the bigger bullet for a time. It all starts back in 1986, during the Miami FBI shootout.

The quick version is a bunch of agents got in a shootout with a couple of guys and their handguns barely did anything. Most were carrying .38 Special or 9mm and things did not go well.

For a time, the FBI switched to handguns in 10mm, which satisfied their ballistic requirements. However, the recoil was a bit much for some agents, so they created a weaker load. Then they noticed the plus-size frame of the 10mm caused problems for a lot of agents - difficult to conceal, hard to operate single-handed with the bigger grip housing, etc. - and thus they had a quandary.

Luckily, Smith and Wesson realized the 10mm case could be cut down and still hold the same powder charge as the weakened FBI load. The smaller round could also work in a pistol frame sized for 9mm and thus, the round was born.

It outclassed the 9mm in the ballistic testing of the day, and impressed enough law enforcement agencies over the years to get quite the following, as plenty still issue the .40 S&W.

What does it have going for it? Basically, it's the smallest big bullet out there, packing a moderate amount of punch but more - at least in terms of kinetic energy - than 9mm, .380 and .38 Special. Since it fits in the 9mm frame, you can carry more rounds than 10mm or .45 ACP and certainly .357 Magnum and people with smaller hands can handle a .40 pistol pretty well. It isn't .22 LR, but it's easy enough to shoot for most people to hack it with a full size or compact.

So...that's why it's so popular. It's the smallest big bullet out there.

40 vs 9mm: The Little Guy Comes Roaring Back

40 vs 9mm

Why is 9mm - or more formally, 9x19mm Parabellum - so popular? It's just big enough to be really useful, but not so big that it's hard to shoot. That's always been its appeal and certainly why the 40 vs 9mm debate these days so often is settled in favor of the 9mm round in terms of sales.

The 9mm was developed from the 7.65x21mm round (aka .30 Luger) by Georg Luger around the dawn of the 20th century by necking the case up to a .355-inch diameter (9mm) projectile to give it more "oomph."

So, what's good about 9mm? It's easy to shoot in terms of recoil and accurate, so just about anyone can use a 9mm pistol - even a compact or subcompact - without too many issues and get competent relatively easily. Loaded properly, with a good hollow point, it's quite effective on hostile personnel.

However, what made the .40 a more viable alternative back in the day was that 9mm hollow points didn't have a good track record in terms of terminal performance, including in the 1986 Miami shootout. The revised FBI ballistic trials that started a year or two later confirmed as much.

That said, the quality of 9mm ammunition has caught up considerably. In fact, many 9mm loads equal or exceed that of .40 in terms of performance but also shootability these days, which is why the FBI dumped the .40 a couple years ago in favor of Glock 9mm pistols as their main duty weapon.

9mm vs 40: Wear And Tear

Another aspect of the whole 9mm vs 40 caliber war is the wear and tear on the gun. The idea goes that .40 S&W beats the heck out of pistols and beats the heck out of the shooter, which is why people that get into a .40 eventually drop it in lieu of a 9mm.

Here we have something with a basis in reality, but also a crap top of sweeping generalizations that should be addressed if a person is to have a good understanding of it.

Okay, so let's get started.

First, .40 S&W has slightly more chamber pressure, about 2,000 psi more than standard 9mm, which is not really enough to make too much of a difference.

At this point, someone might bring up the "Glock Kaboom," a condition wherein the frame blows out in a Glock 22 or 23. Typically, what happens there is that the case head of the cartridge explodes, causing the frame to fracture with it. What causes this? Typically, it's a handloader that's added too much powder, a bad factory load with the same problem, or weak factory brass.

Not, rest assured, the standard chamber pressure created by the round.

Why does the .40 have the reputation for punishing guns?

The typical .40 S&W projectiles are 155-grain, 165-grain and 180-grain. Typical muzzles velocities for these bullet weights are about 1150 to 1200 fps for most 155 grain loads, 1000 to 1100 fps for 165-gr loads, and just under 1000 fps for the 180-gr loads. In terms of energy, the .40 S&W typically adds an extra 50 ft-lbs as a baseline over 9mm.

And why does that crap matter?

Okay, for two big reasons. First, when it comes to wear on the gun with 9mm vs 40, the lighter projectiles send a bullet out the tube at fairly brisk velocities, which propels the slide back at brisk velocities, as well more overall force. What this means is that the slide is cycling more violently than it is with 9mm.

Especially since what most people tend to prefer shooting in .40 S&W pistols is the lighter grain weights, which we'll come back to momentarily.

What doesn't help, and this is something not everyone gets, is that a lot of gunmakers don't change the spring weight from 9mm to .40. Since the slide is cycling more violently, with more force, a .40 S&W pistol should ideally come with a factory recoil spring that's 2 to 3 lbs heavier than 9mm to tame the recoil force and slow the slide down.

As to more of a beating on the shooter, remember that there are two aspects of recoil: recoil force, literally the amount of force generated by the gunshot - which can be quantified by mere calculation; it's literally a physics equation - and then you have felt recoil, which is what the shooter feels.

Any gun where the slide cycles more violently produces more felt recoil.

And in the modern era of light, compact polymer-framed pistols...the .40 S&W is going to bring the pain. Recoil force for a .40 pistol is roughly double that of a 9mm pistol of the same size and weight, after all. However, if you were to switch to a .40 S&W pistol with a metal frame, shoot the 180-grain bullets to tame the violent cycling (heavier bullets are slower and produce less muzzle energy) and add a stiffer recoil spring to slow down the slide...the shooter might have an easier time of it.

Not as easy as shooting 9mm, but if you felt like you HAD to shoot .40 S&W, that would tame it a bit.

40 vs 9mm: The Straight Dope


Okay, so how to REALLY settle 40 vs 9mm?

Go out and shoot a bit of both. Is there one you hit better with or prefer? Then get that. It's that simple.

We could sit here and compare ballistics all day, but that's not going to...okay, fine. We'll do it anyway.

A (one of them, anyway) standard 9mm load is a 115-grain projectile - ball or hollow point - going at about 1,200 feet per second (depending; it varies by manufacturer) and carrying about 350 foot-pounds (again, depending) of energy. The standard .40 S&W load is a 180-grain bullet at about 1,000 fps (again, depending) with about 400 ft-lbs. The difference in those terms is marginal. Expansion in gel tests usually reveals about the same; marginal advantage at best, which isn't enough to make a serious difference.

Frankly both are kind of weak, even in the handgun realm. One standard .357 Magnum load is a 125-grain bullet at 1,400 to 1,600 fps carrying 500 to 750 ft-lbs of energy, depending. The .44 Magnum, if you feel lucky, punk, has a standard load of 240 grains at about 1,200 fps and around 750 ft-lbs of energy for the practice stuff. A hot load would be like a 270-grain flat-top booking it at 1,450 fps and carrying 1,200 ft-lbs of energy.

Why does that matter? Because even the mighty .44 Magnum doesn't have a perfect record as a man-stopper. No handgun cartridge does; there is no such thing as stopping power (well...maybe a .500 Smith and Wesson) in pistols. Only an accurate hit to the spine, the kneecap or the pelvis compromises ambulatory function to stop a person, and only a hit to the brainstem will drop them permanently.

Thus, we can say that neither 9mm nor .40 is a ballistic wunderkind. They are basically adequate. If you put 'em where they're supposed to go...they'll work.

Here, though, is something else to consider.

The aforementioned 115-gr 9mm load in a standard service gun or compact (like the Glock 19) will produce about 5 ft-lbs of recoil. By contrast, the same size of gun shooting the standard .40 S&W load makes about 10 lbs. Granted, that's the physical recoil; felt recoil will be different and subjective. This can be mitigated by dropping down to a 165-grain load (about 9 ft-lbs) but the point here is .40 is going to be more difficult to shoot.

Therefore, it can be said that 9mm is big enough to be reliably effective and can be shot easily and accurately by most people. Since 9mm ammunition has advanced light years beyond the old HydraShok loads of the 1980s that didn't always work too well, any advantage that .40 S&W enjoyed in terms of terminal performance has been abrogated.

9mm is also cheaper and you can carry more bullets. It should be said.

That said, there are people that just want or prefer a .40, and that's totally fine. There are people who hate it, and that's fine too. The reality here is neither is really "better" than the other, but one has some advantages in terms of mass appeal. Neither is well-suited to any purpose beyond self-defense and target shooting, so that's a non-starter. Neither is really a handloader's playground either.

So...40 vs 9mm...the winner is whichever you like.

About The Author

Writer sam hoober