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9mm vs. .40 caliber: How do the cartridges stack up?

Smith & Wesson released the .40 S&W, and the new cartridge has gained traction, but the 9mm remains far more commonly used — here are some key differences


One of the biggest differences is that 9mm ammunition is generally cheaper because of the disparity in the cost of materials.


In mid-2016, the Federal Bureau of Investigation (FBI) awarded Glock an $85 million contract for new pistols chambered in 9mm Luger. Then in early 2017, the U.S. Army awarded Sig Sauer a $580 million contract to supply a service pistol based on the company’s P320 handgun also chambered in 9mm. The new sidearms will replace the venerable Beretta M9, a 9×19mm Parabellum pistol.

Meanwhile, in the past couple of decades, police departments across the country have departed from the 9mm, electing instead to move to the slightly larger .40 caliber.

So, the debate rages on, and questions continue to be asked (and answered) by proponents of each. Which is better? What differences are there? What are the similarities? Is this a tectonic shift or simply another chapter in the rivalry? Here are some thoughts.

Differing history

For starters, the 9mm is a far older design. Georg Luger designed the 9mm in 1901, releasing it to the market about a year later. Smith & Wesson released the .40 S&W in 1990.

The intention behind the .40 design was to take a parent of the FBI’s 10mm load, shorten the case and enable a larger round in existing 9mm designs without having to make significant modifications to the frame. In the 25 years since, the .40 has definitely gained traction, but the 9mm remains far more commonly used.

The two cartridges have some substantially different characteristics. For example, the .40 caliber cartridge typically sports a heavier bullet with loads between from 135 to 180 grain, compared to between 115 and 147 grain for the 9mm. The heavier bullets of the .40 caliber will be a little slower in velocity. The .40 also delivers more felt recoil and has a slightly higher recoil velocity.

Another difference is that the 9mm round is in pistols around the globe. The .40 caliber pistol is — with some exception — restricted to United States deployment. This is quite probably because there simply are more pistols on the market chambered in 9mm. That’s slowly changing — with more .40 cal guns emerging — but availability of more purchase options as a factor, the 9mm still has a slight edge.

One of the biggest differences is that 9mm ammunition is generally cheaper because of the disparity in the cost of materials. The materials used to make cartridges — particularly the lead, zinc, copper, and tin — are sold by weight (provided that other factors like the number of units are the same) so with less materials used, the cost to manufacture 9mm is slightly less costly than .40 caliber.

Another reason for the cost differential is that there are many more 9mm cartridges sold than .40 caliber.

Differing performance between the 9mm and .40 caliber

In terms of performance, the .40 has the edge. When comparing apples to apples (same brand/bullet design across the calibers) bigger calibers will almost always expand to a larger diameter and penetrate a little further. The bigger the bullet, the bigger the hole it makes. Sometimes, the 9mm will do better in penetration because of its high sectional density and because it easier to push a smaller frontal area through the tissue simulator.

When it comes to performance after barrier penetration (particularly auto glass in the FBI eight-part test) the bigger bullets will typically get more mass through the glass to do more damage to the target.

All that having been said, the margins between the performance of .40 cal vs. 9mm are close enough that in a real world situation, the damage done by each round is — for practical purposes — about the same. Further, the tests which net the results we discuss about penetration and expansion need to be assessed alongside a substantially sized grain of salt.

People are not comprised merely of muscle (which ballistics gelatin simulates). People have bones and vital organs, which affect the lethality of gunshot wounds. Consequently, shot placement and accuracy are far more important determining factors of a round’s lethality than how the gel looks after the test.

Finally, with bullet designs continuing to evolve, there may come a point in time where the performances practically intersect. So on balance, the “bigger hole” argument is a little, well, hollow.

Come to your own conclusions

So, which is better?

The short answer is, “It depends.” It depends on whether or not you have difficulty with the heavier, “snappier” felt recoil of the .40 caliber. It depends on whether or not you want to save money while shooting more in training with the 9mm. It depends on whether or not you want to drill slightly larger holes with a slightly smaller number of bullets. It depends on the load you choose in either cartridge.

Do yourself a favor.

Shoot both.

A lot.

Then decide.

Either way, make sure you keep training hard, ensure your maintain your positive, winning mindset, and stay vigilant always.

Doug Wyllie writes police training content on a wide range of topics and trends affecting the law enforcement community. Doug was a co-founder of the Policing Matters podcast and a longtime co-host of the program.