The .40 S&W cartridge, once hailed as the ideal compromise between stopping power and manageable recoil, experienced a meteoric rise to prominence in law enforcement and civilian markets alike. Yet, in what seemed like the blink of an eye, its star faded, with many police departments returning to the venerable 9mm. This is the story of the .40 S&W, its ambitious origins, widespread adoption, and eventual decline.
.40 cal ammunition is very readily available in FMJ and/or Defense Ammo
The Tragic Genesis of a Compromise
To understand the .40 S&W, we must first examine the infamous 1986 Miami-Dade FBI shootout. This tragic event, in which two FBI agents were killed and five others wounded, highlighted a critical perceived deficiency in the then-standard 9mm Parabellum cartridge that had been around since Austrian engineer George Luger invented it in 1902 and was adopted for use in the German military starting in 1904. Despite multiple hits during the shootout, one of the perpetrators continued to fight, leading many to believe that the 9mm lacked sufficient “stopping power.” The FBI, seeking a more effective round, began experimenting. Their initial foray was a 10mm Auto load, a powerful cartridge that, while effective, created substantial recoil that proved too unwieldy for many agents, particularly those with smaller hands, hindering fast and accurate follow-up shots.
Recognizing the need for a cartridge that offered enhanced performance over the 9mm without the brutish recoil of the full-power 10mm, Smith & Wesson and Winchester collaborated to create a new round. The solution was elegant in its simplicity: they took the 10mm Auto casing and shortened it to fit into 9mm-sized pistol frames but with a bullet diameter of 10.2mm. The result was the .40 S&W, officially introduced in 1990. It effectively replicated the performance of the FBI’s reduced-power 10mm load, propelling a 180-grain bullet at approximately 950-1000 feet per second. It seemed like the perfect solution at the time.
The .40 S&W immediately gained traction. It significantly increased bullet weight and diameter compared to the 9mm (typically 115-147 grains for 9mm vs. 155-180 grains for .40 S&W), promising greater energy transfer and a larger wound channel. This translated to a perceived advantage in incapacitating threats for law enforcement, addressing the concerns that arose from the Miami-Dade shootout.
.40 cal hybrid hollow point projectile
The Reign of the .40: Widespread Adoption by Law Enforcement
The early 1990s saw a rapid and enthusiastic embrace of the .40 S&W by law enforcement agencies across the United States. Departments transitioned en masse from their aging .38 Special revolvers and even their 9mm semi-automatics to pistols chambered in .40 S&W. In particular, the Glock 22 and 23 became ubiquitous, known for their reliability and capacity. Other manufacturers quickly followed suit, offering a wide array of .40-caliber pistols.
The logic behind this shift was compelling. The .40 S&W was considered a “best of both worlds” solution. It provided more “knockdown power” than the 9mm, assuaging fears of under-penetration or insufficient incapacitation, while still being controllable enough for most officers to shoot effectively, unlike the full-power 10mm Auto. Training regimens were updated, holsters were replaced, and the .40 S&W became the de facto standard for duty weapons in many agencies for nearly two decades.
Beyond law enforcement, the .40 S&W also found a strong following in the civilian market. Concealed carry permit holders appreciated the perceived increase in self-defense effectiveness, and competitive shooters enjoyed the balance of power and shootability. Ammunition manufacturers ramped up production, and the .40 S&W became a staple on gun store shelves.
The 9mm’s Resurgence and the .40’s Decline
Despite its dominant position, however, cracks began to show in the .40 S&W’s armor. Over time, several factors contributed to its gradual, and then rapid, abandonment by law enforcement agencies in favor of the 9mm.
One of the primary drivers for the shift back to 9mm was the advancement in ammunition technology. Modern 9mm hollow-point bullet designs have dramatically improved expansion, penetration, and consistency. No longer are 9mm rounds simply “ice picks” as some once disparagingly called them. Contemporary 9mm duty ammunition performs exceptionally well in ballistic gel tests, often rivaling or even surpassing the performance of .40 S&W rounds. The “stopping power” argument, once so compelling for the .40, became less distinct as 9mm technology caught up.
Recoil and Controllability also played a significant role. While more manageable than the 10mm, the .40 S&W still generated noticeably more recoil than the 9mm, translating to slower follow-up shots, increased muzzle flip, and greater shooter fatigue, especially during extended training sessions. For officers, particularly those with less experience, smaller stature, or difficulty with their grip, controlling a .40 S&W under stress could be challenging. In high-stress encounters, the ability to deliver multiple, accurate hits quickly often outweighs the marginal theoretical advantage of a larger caliber. The 9mm, with its softer recoil, allows for faster target reacquisition and more precise shot placement, arguably more critical for effective incapacitation.
Capacity became another crucial consideration. Because the .40 S&W round is larger, pistols chambered in it generally hold fewer rounds than their 9mm counterparts of the same size, the same way that a 1911 in .45ACP holds fewer rounds than one chambered in 9mm. In a world where active shooter incidents and multiple-threat scenarios are a growing concern, maximizing ammunition capacity without significantly increasing the size of the firearm became a priority for law enforcement. A compact 9mm pistol could often carry as many rounds as a full-size .40 S&W, and a full-size 9mm could carry significantly more.
Cost and logistics also factored into the decision, with 9mm ammunition being generally less expensive to manufacture and purchase than .40 S&W. These cost savings can be substantial for large law enforcement agencies that purchase hundreds of thousands, if not millions, of rounds annually for training and duty use. Furthermore, training on a platform with less recoil can lead to more efficient use of ammunition, as officers are less prone to flinching or developing bad habits from anticipating recoil.
Finally, a growing body of statistical data and empirical evidence began to emerge, suggesting that there was no significant real-world difference in “stopping power” between modern service calibers like the 9mm, .40 S&W, and .45 ACP when using modern, duty-grade ammunition and striking vital areas. Subsequently, the emphasis shifted from raw caliber size to shot placement and the efficacy of modern bullet designs.
The Full-Scale Retreat of the .40
Starting in the mid-2010s, the trickle of departments abandoning the .40 S&W and returning to the 9mm became a torrent. Major agencies, including the FBI, announced their switch back to 9mm. The FBI’s decision, in particular, held significant weight, as their initial perceived need drove the creation of the .40 S&W in the first place. However, their rigorous testing and analysis concluded that modern 9mm ammunition, coupled with the advantages of reduced recoil and increased capacity, made it the optimal choice for their agents.
The Glock 22 was the Go-To for LE departments when the .40 reigned supreme
Police departments across the country followed suit, driven by the same considerations. Agencies that had invested heavily in .40 S&W firearms found themselves gradually phasing them out, either by issuing new 9mm pistols or allowing officers to choose approved 9mm firearms. Soon, the market for used .40 S&W police trade-ins was flooded, a clear indicator of the shift.
The Legacy of the Forgotten Round
The .40 S&W’s rapid rise and fall is a fascinating case study in firearms development and adoption. It was born from a genuine need, filled a perceived void, and reigned supreme for a time. However, the relentless march of technology, coupled with a re-evaluation of priorities in law enforcement, ultimately led to its decline.
While the .40 S&W may no longer hold the top spot in law enforcement holsters, it remains a capable cartridge. Many civilians still prefer it for self-defense, and its presence in the shooting world is far from over. Yet, its story is a powerful reminder that in the world of firearms, what is perceived as “cutting edge” today can quickly become a relic of yesterday, as innovation and evolving tactical doctrines continue to shape the tools of those who protect and serve. The 9mm, once thought to be underpowered, has returned to its throne, a testament to its enduring versatility and the remarkable advancements in modern ammunition technology.
