9mm VS 40: Why the .40 Caliber Round Fights On

Lately, the .40 S&W has been awash in a stormy sea of unflattering ink. But why are some experts convinced that the .40 is dead and buried? The most common answer is that improvements in 9mm ammunition have made the .40 obsolete. Well, it’s true that a number of federal and local police agencies have switched to the 9mm. But are some people just getting on the 9mm bandwagon, assuming that what’s good for the police is good for them? And just because the 9mm is getting better, does it mean the .40 is getting worse? We discuss this in our evaluation of 9mm VS 40 cal.

9mm VS 40 Cal

No, the .40 is not getting worse. Many people declared the .45 ACP dead when most American military units traded their .45-caliber 1911s for Beretta 9mms. However, the .45 ACP didn’t disappear, and .45-caliber pistols still sell briskly.

People even buy “obsolete” .38 Special and .357 Magnum revolvers for personal protection. This is despite the fact that police departments began to transition to semi-autos in the late 1970s. So, I’ll ask again: Why is it that people believe the .40 S&W is dead?

Is the 9mm Really Better?

The question is, better for who? Switching to 9mm made sense for the military because our NATO allies standardized the 9mm. In addition, 9mm ammo is about half the price of .45 ACP. Not to mention, many 9mm semi-autos have a significant firepower advantage over most .45s.

In the late 1950’s I saw an Army training film on the tactical use of the M1911 .45 pistol. It demonstrated that firing double taps with the 1911 significantly improved the chance of scoring a vital hit.

Most military .45s held eight shots. The “new” SIG M17 holds a total of 18 shots using the flush-fit magazine. Would you rather keep shooting or spend your time reloading during a human wave attack?

So, from the perspective of the military, the 9mm has a clear advantage over the .45. But what about civilians and police armed with the .40? Is the 9mm better for them?

Are Capacity and Recoil Viable Arguments?

People who claim that the .40 is dead often argue you can get more 9mm rounds into similar size magazines. However, the difference usually amounts to 1 or 2 more 9mm rounds in similar guns using flush-fitting magazines.

That’s a small advantage, and it gets smaller when you consider that most shooting incidents rarely involve a person firing more than the 16 rounds that fit in my Ruger SR40.

The M&P 9c magazine (left) holds15 rounds, but you need a bigger magazine to hold 15 rounds of .40 S&W (right). The .40 therefore requires a bigger grip frame to hold the bigger magazine and that makes it a bit less concealable. The 9mm holds a slight edge VS the 40 in this aspect.

Next they argue that the .40 S&W has too much recoil. This is a difficult claim to evaluate because each caliber has so many different loads. However, CorBon’s well-respected 9mm +P 115-grain JHP produces 3.7 pounds of free recoil in a fully-loaded S&W M&P9c.

Compare that to the 4.7 pounds produced by Winchester’s .40 S&W 165-grain PDX-1 in my fully-loaded Ruger SR40. So, in this particular case, the 9mm does kick less. In addition, the pressure curve of the .40 is quite steep, making the .40 recoil quite sudden.

The Terminal Effect

Up to this point, it looks like the 9mm has the advantage. But we haven’t yet looked at the terminal effect of each cartridge. Using the data from the Lucky Gunner Labs website, I reviewed the muzzle energy, penetration, and expansion produced by the 9mm and .40 S&W loads selected by Lucky Gunner.

CORBON’s 9mm 115 gr DPX and Winchester’s 165 gr PDX-1 both met the author’s criteria for good terminal performance in the Lucky Gunner Labs tests in our 9mm VS 40 comparison.

For a load to be included in my analysis, every bullet fired in the test using that load had to fully expand and penetrate at least 12 inches and no more than 18 inches in denim-covered Clear Ballistics gel used by Lucky Gunner. Loads meeting these strict criteria delivered ideally consistent performance.

The 9mm test gun was a Smith & Wesson M&P9c and the .40 was a Glock 27. Both of which are common compact concealed carry pistols. I used Lucky Gunner’s data because it is the largest database I could find that’s easily available to our readers. Also, because it offers a controlled comparison of some generally available personal defense loads in 9mm and .40 S&W.

Lucky Gunner Results

Interestingly only seven of the 52 9mm loads tested by Lucky Gunner (13 percent) met my criteria for ideally consistent performance. This is compared to 11 of the 37 (30 percent) of the .40 S&W loads.

The average penetration for the 9mm was 14.02 inches, while the .40’s average was 16.3 inches. The average expansion for the 9mm was 0.59 inches, while the average for the .40 was 0.77.

In addition, the average muzzle energy for the 9mm was 304 fpe. However, the average muzzle energy produced by the .40 was 373 fpe. It’s pretty clear that in Lucky Gunner’s database, the best-performing .40 S&W loads exhibited superior terminal performance compared to the best 9mm loads. Specifically with respect to controlled penetration, muzzle energy, and expansion. So why is anyone declaring that the .40 is dead?

A Switch to 9mm

LE agencies were relatively quick to adopt the .40. Mainly because it was designed to make up for the deficiency in penetration shown by a 9mm bullet in the infamous Miami Incident in 1986.

In that incident, a 115-grain 9mm JHP failed to penetrate deeply enough to end the shooting spree of Michael Platt. He went on to kill two FBI agents and seriously wound several others. But in the three decades since the .40 appeared, the FBI and several agencies switched to 9mm.

One reason was that many of today’s law enforcement recruits have little experience with firearms. Because of this, they face a steep learning curve when it comes to being proficient with the .40. This creates increased training requirements and costs.

In addition, agencies also learned that the steep pressure curve of the .40 can be hard on guns. Not to mention, the costs of repairing and replacing .40s over time mounted up over the decades.

This airplane hostage rescue from 10 yds. was shot from low ready.

Then there’s the assumption that less expensive 9mm ammo would always be cheap and available. Specifically due to the large number of 9mm guns in service worldwide. Surely, ammo companies would always have a good supply of 9mm ammunition on hand.

Recent ammo famines have proved just the opposite. In present times, the rush to hoard ammo has rapidly depleted stocks of 9mm ammo and almost tripled its cost. However, the slower-selling .40 S&W has been more available and sometimes even less expensive!

Last Licks

In the end, a .40 S&W pistol is like a high-performance sportscar. It’s not for everyone. Generally, .40-caliber ammo is more expensive than 9mm. In addition, the .40 requires closer attention to maintenance and takes more skill to shoot well. On the other hand, many .40-caliber loads outperform 9mm loads in the ballistics lab.

So, some will switch to 9mm, and some will stay with .40 because it offers a better balance of firepower and on-target effectiveness. Because of that, the .40 will be around for a long time despite recent “rumors of its demise.”

This airplane hostage rescue from 10 yds. was shot from low ready. Neutralizing the threat generally requires a head shot in a restricted space. The head is a difficult part of the body to hit when it the target is motionless. It can be even more difficult target when you have to shoot quickly in an aircraft which is an unstable platform.

This article was originally published in the Combat Handguns January/February 2022 issue. Subscription is available in print and digital editions at OutdoorGroupStore.com. Or call 1-800-284-5668, or email subscriptions@athlonmediagroup.com.