History of the .40 S&W: Origins, Development & Legacy

Few handgun cartridges went from a new introduction to widespread law-enforcement use as quickly as the .40 Smith & Wesson.

Introduced in 1990, the .40 S&W arrived at exactly the right moment. American law-enforcement agencies were reconsidering what they wanted from a duty handgun, semiautomatic pistols were rapidly replacing revolvers, and the FBI's ammunition research was influencing how defensive handgun cartridges were evaluated.

The .40 S&W was designed to occupy an interesting middle ground. It offered a larger and heavier bullet than the 9mm while fitting into handguns that could be smaller and easier to handle than many pistols chambered for the 10mm Auto.

Within only a few years, .40 caliber pistols were everywhere in American law enforcement.

To understand why, however, the story has to begin before the .40 S&W existed.

Before the .40 S&W: The Rise of the 10mm Auto

The .40 S&W owes much of its existence to the 10mm Auto.

The 10mm emerged during the early 1980s as a powerful semiautomatic pistol cartridge. Its development involved ideas that stretched back even further, including experiments with .40 caliber handgun cartridges during the 1960s and 1970s.

The 10mm eventually appeared commercially with the Bren Ten pistol and Norma ammunition. Early 10mm ammunition offered considerably more velocity and energy than the service handgun cartridges commonly used at the time.

That performance attracted attention.

But the event that ultimately put the 10mm on a path toward federal law-enforcement use occurred in Florida in 1986.

The 1986 FBI Miami Shootout

On April 11, 1986, FBI agents confronted two heavily armed robbery suspects near Miami, Florida.

The resulting gunfight became one of the most studied incidents in modern American law-enforcement firearms history.

Two FBI agents were killed and several others were wounded.

One particular shot received enormous attention during the investigation. A 9mm bullet fired by an FBI agent penetrated the suspect but stopped short of reaching the heart. The incident became part of a much larger examination of handgun ammunition performance.

The lessons drawn from Miami would eventually influence ammunition development far beyond the FBI.

The FBI Changes the Way Handgun Ammunition Is Tested

After Miami, the FBI conducted extensive research into handgun ammunition.

Rather than judging ammunition primarily by caliber, velocity or muzzle energy, investigators placed greater emphasis on what bullets actually did after impact.

The FBI developed testing using calibrated 10 percent ordnance gelatin and evaluated bullet penetration and expansion, including performance after passing through intermediate barriers.

That testing philosophy became enormously influential.

Ammunition manufacturers began designing defensive bullets around more demanding performance standards, and the FBI's protocols eventually became an important reference point throughout the ammunition industry.

The search for a new service cartridge also led the Bureau toward the 10mm Auto.

The FBI and the 10mm Auto

The 10mm offered impressive performance, but the FBI did not simply settle on the hottest ammunition available.

Testing showed that a reduced-velocity 10mm load could provide the terminal performance the Bureau wanted without requiring the full velocity potential of the cartridge.

Federal developed a 180-grain 10mm load at approximately 950 feet per second for the FBI.

This is an important part of the story because it corrects a common oversimplification.

You will sometimes hear that the FBI adopted full-power 10mm ammunition, discovered agents couldn't handle the recoil, and then downloaded it.

The history is more complicated.

The reduced-velocity 10mm ammunition was developed as part of the Bureau's evaluation process, before full-power 10mm became standard FBI issue.

The real question became increasingly obvious:

If the FBI wanted approximately 180-grain bullets at reduced 10mm velocities, did it really need the large 10mm cartridge case to accomplish it?

Smith & Wesson saw the opportunity.

From the 10mm to the .40 S&W

The 10mm Auto uses a relatively long cartridge case and generally requires a correspondingly larger handgun platform.

But the FBI's reduced-velocity ammunition wasn't taking advantage of the 10mm's full ballistic capacity.

Smith & Wesson realized similar performance could be achieved using a shorter cartridge.

The case was shortened while retaining the .40 caliber projectile.

The resulting cartridge could fit into handgun platforms closer in size to those already being used for 9mm pistols.

That was a major advantage.

A law-enforcement agency could potentially obtain a larger-diameter, heavier projectile without requiring every officer or agent to handle a large 10mm-size pistol.

Smith & Wesson partnered with Winchester Ammunition to bring the concept to market. Smith & Wesson describes the cartridge as jointly developed with Winchester in collaboration with the FBI's request for reduced-power 10mm performance.

The new cartridge received a straightforward name:

.40 Smith & Wesson.

The .40 S&W Arrives in 1990

The .40 S&W was formally introduced in January 1990.

Smith & Wesson introduced its Model 4006 pistol alongside the new cartridge. The Model 4006 was a stainless-steel, third-generation Smith & Wesson semiautomatic designed specifically around the new chambering.

The timing could hardly have been better.

Police departments throughout the United States were transitioning toward higher-capacity semiautomatic pistols.

The 9mm offered capacity and controllability.

The .45 ACP offered a larger, heavier bullet but generally with reduced magazine capacity in the pistols of the period.

The new .40 S&W seemed to offer a compromise between them.

That concept proved extremely attractive.

Glock Moves Quickly

Smith & Wesson's name was on the cartridge, but it wasn't alone in recognizing its potential.

Glock moved extremely quickly with its own .40 S&W pistols.

The Glock 22 and compact Glock 23 became closely associated with the cartridge and eventually became common sights in police holsters throughout the United States.

This helped establish something that would define the .40 S&W for the next two decades.

It wasn't merely another commercial handgun cartridge.

It became a law-enforcement cartridge.

Why Police Departments Embraced the .40 S&W

The cartridge arrived during a major transition in American police firearms.

Departments wanted greater ammunition capacity than traditional revolvers could provide, reliable semiautomatic pistols and effective defensive ammunition.

The .40 S&W appeared to provide a useful balance.

Its shorter cartridge length allowed manufacturers to build .40 caliber pistols using platforms relatively close to their 9mm designs.

Magazine capacity was generally greater than comparable .45 ACP service pistols of the era.

At the same time, the cartridge could fire heavier bullets than were typical in 9mm ammunition.

For agencies looking for something between 9mm and .45 ACP, the .40 S&W seemed almost purpose-built for the job.

In many ways, it was.

The .40 S&W Becomes a Law-Enforcement Standard

During the 1990s and 2000s, .40 S&W adoption expanded rapidly.

Federal, state and local agencies adopted pistols chambered for the cartridge.

Manufacturers responded with an enormous selection of firearms.

Smith & Wesson, Glock, SIG Sauer, Heckler & Koch and other major manufacturers produced .40 S&W handguns.

Ammunition companies developed increasingly sophisticated defensive loads.

The 155, 165 and 180 grain bullet weights became familiar choices, with 180 grains becoming particularly closely associated with the cartridge.

For a generation of American shooters, seeing ".40" stamped on the slide of a police pistol became completely ordinary.

The FBI Eventually Adopts .40 S&W

The FBI's ammunition research helped create the conditions that led to the .40 S&W, and the Bureau later adopted the cartridge itself.

That further strengthened the .40's reputation.

Once a cartridge has widespread law-enforcement adoption, manufacturers have a powerful incentive to continue improving both firearms and ammunition.

That happened throughout the .40 S&W era.

Hollow-point technology improved.

Bonded bullets became more common.

Manufacturers refined bullets for more consistent expansion, penetration and performance through intermediate barriers.

Ironically, those improvements would eventually help another cartridge take market share back from the .40 S&W.

That cartridge was the 9mm.

Improvements in 9mm Ammunition Change the Equation

The .40 S&W became popular partly because agencies wanted better terminal performance than they believed contemporary 9mm ammunition provided.

But ammunition technology didn't stand still.

Modern jacketed hollow-point bullets became much more sophisticated.

Manufacturers improved bullet construction, expansion consistency and barrier performance.

As 9mm defensive ammunition improved, agencies began reconsidering whether the additional recoil and reduced capacity associated with .40 S&W were still necessary.

The FBI eventually moved back toward 9mm, and many other agencies followed.

This reversal had a major effect on the commercial handgun market.

Why Law Enforcement Moved Back to 9mm

The decision wasn't simply that .40 S&W had somehow stopped working.

Instead, the balance of advantages had changed.

Modern 9mm ammunition could provide strong terminal performance while generally producing less recoil.

Lower recoil can help shooters recover between shots.

9mm pistols generally offer greater magazine capacity than otherwise comparable .40 S&W models.

Ammunition can also be less expensive, which matters enormously when an agency purchases large quantities for training.

As modern 9mm ammunition narrowed the performance gap, the practical advantages of 9mm became more compelling.

The .40 S&W's dominance began to decline.

Did the .40 S&W Fail?

No.

That is one of the biggest misconceptions surrounding the cartridge today.

The .40 S&W didn't disappear because it was ineffective.

It lost market share because firearm and ammunition technology changed around it.

The cartridge successfully served law-enforcement agencies for decades.

Millions of pistols chambered in .40 S&W were produced.

It influenced defensive ammunition development and became one of the defining American service cartridges of the 1990s and 2000s.

A cartridge doesn't need to remain the most popular option forever to have been successful.

By that measure, the .40 S&W was enormously successful.

.40 S&W vs. 10mm Auto

The relationship between .40 S&W and 10mm Auto remains important today.

Both use the same nominal .400-inch bullet diameter, but the cartridges are not interchangeable.

The 10mm has a longer case and significantly greater ballistic potential.

Full-power 10mm ammunition can propel heavy bullets considerably faster than typical .40 S&W loads.

The .40 S&W gives up that maximum performance in exchange for a shorter cartridge that can fit into smaller handgun platforms.

That tradeoff was fundamental to its original purpose.

The .40 S&W was never intended simply to duplicate full-power 10mm.

It was intended to provide the performance level the FBI found useful from reduced 10mm ammunition in a more practical cartridge and handgun package.

For actual velocity, energy and barrel-length comparisons, see our .40 S&W Ballistics guide.

The .40 S&W in the Civilian Market

Law-enforcement adoption gave the .40 S&W enormous visibility, but civilian shooters embraced it as well.

The cartridge became common for personal protection, home defense, recreational shooting and competition.

Many shooters purchased the same types of pistols carried by police departments.

Others simply liked the balance between bullet weight, handgun size and magazine capacity.

When police agencies later began transitioning back to 9mm, large numbers of used .40 S&W pistols entered the commercial market.

That created another generation of civilian .40 owners.

Even today, the installed base of .40 caliber pistols is enormous.

The Competition Legacy of .40 S&W

The .40 S&W also developed an important following in practical shooting competition.

Certain competition divisions use scoring systems where ammunition meeting a specified power factor receives different scoring treatment.

The .40 S&W became particularly useful because competitors could make Major power factor while still using a relatively compact semiautomatic cartridge.

This gave the .40 a life beyond police duty use and personal protection.

Competition shooters helped keep interest in the cartridge alive even as law-enforcement adoption declined.

The .40 S&W Today

The .40 S&W is no longer the dominant new service-pistol cartridge it once was.

9mm has reclaimed that position.

But declaring the .40 S&W dead ignores the enormous number of firearms already chambered for it and the continued availability of ammunition.

Major ammunition manufacturers still produce .40 S&W defensive and training loads.

Millions of shooters still own .40 caliber pistols.

The cartridge remains capable of firing heavy .400-inch bullets at useful handgun velocities from relatively compact firearms.

For someone who already owns and shoots a .40 S&W pistol well, the cartridge remains entirely practical.

Our Best .40 Cal Ammo guide covers current ammunition choices for defensive use and range training.

The Legacy of the .40 S&W

The .40 S&W occupies a unique place in American firearms history.

It wasn't designed for a world war.

It wasn't created during the black-powder era.

It wasn't developed primarily for hunting.

It grew out of a very specific period in modern law-enforcement history.

The 1986 Miami gunfight forced the FBI to reconsider how defensive handgun ammunition should be evaluated. The resulting research led toward the 10mm Auto, reduced-velocity 10mm ammunition and ultimately the idea that similar performance could be packaged into a shorter cartridge.

Smith & Wesson and Winchester turned that idea into the .40 S&W.

The cartridge arrived in 1990 and rapidly became one of America's dominant law-enforcement handgun chamberings.

Its dominance eventually faded as 9mm ammunition improved and agencies reconsidered recoil, capacity and training.

But the .40 S&W had already left its mark.

It influenced handgun design, defensive ammunition development, police firearms policy and an entire generation of American shooters.

More than three decades after its introduction, the .40 S&W remains one of the most recognizable modern American handgun cartridges.

Frequently Asked Questions About the History of .40 S&W

When was the .40 S&W invented?

The .40 S&W was introduced in January 1990. Smith & Wesson introduced its Model 4006 pistol alongside the new cartridge.

Who invented the .40 S&W?

The cartridge was developed through a partnership involving Smith & Wesson and Winchester, with its origins closely tied to FBI ammunition requirements and reduced-velocity 10mm performance.

Why was the .40 S&W created?

The cartridge was designed to provide performance similar to reduced-velocity 10mm ammunition in a shorter cartridge that could fit into more compact handgun platforms.

Did the FBI create the .40 S&W?

Not directly. FBI ammunition testing and its interest in reduced-velocity 10mm performance provided much of the impetus, while Smith & Wesson and Winchester developed and commercialized the .40 S&W.

Is .40 S&W just a shortened 10mm?

That is a useful simplified description because the .40 S&W uses a shorter case and the same nominal bullet diameter, but the cartridges have different performance capabilities and should be treated as distinct chamberings.

Why did police use .40 S&W?

The cartridge offered a combination of relatively heavy bullets, semiautomatic-pistol capacity and the ability to fit into handguns smaller than traditional 10mm platforms.

Why did police departments move away from .40 S&W?

Improvements in 9mm ammunition made the smaller cartridge increasingly attractive because it generally offered lower recoil, greater magazine capacity and lower training costs while meeting modern defensive performance requirements.

Is .40 S&W obsolete?

No. It has declined substantially from its peak in law-enforcement use, but millions of .40 S&W firearms remain in circulation and factory ammunition continues to be produced.

Continue Exploring .40 S&W

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History of the .40 S&W: Origins, Development & Legacy

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