The .40 S&W cartridge, left, was developed from the larger 10mm cartridge. It has the same diameter bullet and case, but is shorter overall.

The .40 Smith & Wesson cartridge came to be because of a tragic firefight in Florida 31 years ago: the infamous “Miami Shootout” between eight FBI agents and two serial bank robbers. In the end, two agents were killed and five were wounded. Such an outcome seemingly never should have happened, because the agents shot the bad guys over and over, but the rounds that the agents had shot at the suspects—most of them 9mm—appeared to be ineffective.

It took six hits to kill one of the robbers and 12 bullets to kill the other. Some of the bullet wounds were in vital areas. Toxicology reports showed that the suspects had no chemical boost from any drugs to help them withstand the hits. Instead it was the poor performance of the cartridge and bullets that allowed the bad guys to keep shooting. It was a catastrophic event for the bureau.

Following the disaster in Miami, it was clear to the FBI that the 9mm—9×19 Parabellum, 9mm Luger, or 9×19 NATO, take your pick—was not adequate. They recognized the failure and put out word that they were looking for a new cartridge. They had decided that size does indeed matter with bullets, and they wanted a cartridge that was bigger than the 9mm that failed them.

An empty police revolver on the ground in the aftermath of the 1986 Miami Shootout with the shells partially ejected from an open cylinder. (Right) the robbery suspects' long guns on the ground to the
A police revolver on the ground with the shells partially ejected from an open cylinder in the aftermath of the 1986 Miami Shootout. On the right, a photo of the robbery suspects’ long guns stacked together after the shooting stopped. photo from youtube

The 10mm Tests

One that got their attention was the 10mm Auto. The cartridge had been introduced in 1983 and was getting a lot of press in the mid-eighties. Several shooters, including Jeff Cooper, developed the 10mm as the ultimate pistol-fighting cartridge. They used a cut-down .30 Remington case and the 180-grain .40-caliber bullet used in the .38-40 Winchester cartridge. Norma loaded the initial ammo, and the “Bren Ten” was the pistol. Sonny Crockett carried one on “Miami Vice” back when he was the coolest guy on the planet. The “Bren Ten” didn’t last long, but Colt and other companies began making guns chambered in 10mm.

The FBI took a look at the 10mm and decided it was just what they needed.

Bren Ten
Sonny Crockett (Don Johnson) made the 10mm Dornaus & Dixon Bren Ten pistol famous on TV’s Miami Vice. The Bren was essentially a beefed-up CZ 75. photo from

Although the 10mm is a powerful, effective and well-respected self-defense cartridge, these days it’s promoted mostly as a hunting cartridge and one for defense against grizzly attacks (though it’s not the best for that purpose, say some experts).

While on the light side compared to most hunting revolver cartridges, it is one of the few in a semi-auto handgun that is powerful enough to be ethically used for hunting big game. The ballistics are almost identical to the .38-40 Winchester in a rifle (which is the cartridge I used to take my first whitetail deer many years ago).

FBI agents soon started complaining about the recoil, so the bureau began testing ammo with a smaller powder charge.

The story goes that during tests, the FBI Firearms Training Unit’s Special Agent-in-Charge John Hall brought in his personal Colt Delta Elite 1911 chambered for the 10mm cartridge. They tested his reduced-power handloads and found that a 180-grain bullet with a muzzle velocity of 1,000 feet per second was the magic they were seeking. They asked Smith & Wesson to build some guns, but it wasn’t long before somebody realized that they didn’t need the same large case to hold the smaller powder charge. So the case length was reduced from .992-inch to .850-inch, and the primer size was changed from Large Pistol to Small Pistol.

That’s how the .40 S&W was born.

Federal’s 135-grain Personal Defense load in .40 S&W has lower recoil than other .40 loads but still offers plenty of power.
Federal’s 135-grain Personal Defense load in .40 S&W has lower recoil than other .40 loads, but still offers plenty of power. author photo

Power in a Small Package

The overall cartridge length for the .40 S&W is actually slightly less than that of the 9mm cartridge, which means the cartridge could fit into 9mm-size handgun, but would provide a substantial boost in power.

Winchester made the first ammo, and the initial loads for the .40 S&W used a 180-grain bullet with a muzzle velocity of 985 feet per second. This generates 388 foot-pounds of muzzle energy. Bullet weights later ran the scale from 125 grains to 200 grains. Some of those loads for the .40 S&W approach 500 foot-pounds of muzzle energy, while the 9mm struggles to produce much over 350 foot-pounds.

More important is that the .40 S&W has a larger, heavier bullet than the 9mm. Handguns do not produce a lot of muzzle energy when compared to a rifle, so they depend on bullet diameter for their terminal ballistic performance. Simply put, a larger bullet punches a bigger hole and damages more important body parts.

A Fast Start

The .40 S&W cartridge debuted January 17, 1990, along with the new Smith & Wesson Model 4006 pistol. Glock also announced pistols chambered in .40 S&W at about the same time, and got them to the market ahead of Smith & Wesson. It wasn’t long before every serious defensive pistol maker was chambering the cartridge.

The FBI switched to the .40 S&W, discarding the 10mm like a lover after a one-night stand (though the FBI Hostage Rescue Team and SWAT teams continued to use the 10mm.)

The .40 Smith & Wesson soon became the preferred cartridge for a wide range of law enforcement agencies. It’s also one of the top handgun cartridges chosen for self-defense by law-abiding citizens.

No discussion of the cartridge, though, can be complete without acknowledging a dark side. The .40 S&W, particularly in older Glock pistols, has been reported to have case rupture failures. This is due to the unsupported area around the case head in some barrels. New factory loads are usually not a problem. Most of the issues are from reloads where the case is worked and becomes weak. Another theory is that the bulged area in the reloaded case is not completely removed in resizing and causes the gun to fire when slightly out of battery. It’s also thought that some of the loads were loaded to an unsafe pressure level.

I don’t hear much about this issue anymore, and I suspect it’s been pretty much addressed. On a personal note, I have fired thousands of.40 S&W handloads, many from an older G22, and have never experienced a single problem. Redding makes a special die that will remove the “Glock bulge” from the case, and I use it with all my handloads.


Handgun bullet performance has improved over the years, but the differences between these three popular calibers still stand. Here’s how they compare.

The Great Debate: 9mm, .40, or .45

The Rebound

Surprisingly, the FBI is reversing their decision and going back to the 9mm. I fear that history may well be about to repeat itself.

Many argue today that new bullet technology has changed everything, but they are ignoring a few key points. First, that technology applies to every other cartridge, so while it has advanced the 9mm’s terminal performance, it has also advanced the terminal performance of every other cartridge equally. The 9mm remains on the bottom rung when comparing the big three defensive handgun cartridges: 9mm, .40 and the .45 ACP. That’s simple physics. Yet, the trend has moved away from the .40 S&W in favor of the 9mm both in law enforcement and civilian sales. The lower recoil of the 9mm seems to outweigh any thoughts about terminal performance.

Some grumpy traditionalists labeled the .40 S&W a “compromise” cartridge and, in an amazing meld of the generations, the new Internet warriors have decided they don’t like the .40 S&W for many of the same reasons.

Currently that leaves the .40 S&W’s future in a bit of limbo, as I am told that sales have dropped substantially. Fads come and go, though, and I suspect in a few years it will be “rediscovered” and again fall into fashion with those who carry a handgun in defense of their lives.

Personally, I don’t blindly follow any trends and I still see the .40 S&W as one of the best choices for defensive pistols. It can be chambered for 9mm-sized handguns, while providing a higher level of performance than the 9mm cartridge. Nothing has changed with that, except public opinion, which I find to be pretty untrustworthy in most situations.