Why the FBI Ditched 9mm for .40 S&W — Then Switched Back

The Shootout That Changed Everything

On the morning of April 11, 1986, eight FBI agents in five vehicles converged on a stolen car in an unincorporated area of Miami-Dade County, Florida. Inside were Michael Platt and William Matix — two former military men responsible for a string of armored car robberies and at least one murder.

What followed was the most consequential gunfight in American law enforcement history. In under five minutes, approximately 145 rounds were exchanged. When the shooting stopped, both suspects were dead — but so were two FBI agents: Special Agent Benjamin P. Grogan, age 53, and Special Agent Jerry L. Dove, age 30. Five more agents were wounded.

The FBI's post-shooting analysis would trigger a decades-long caliber debate that reshaped law enforcement ammunition, spawned an entirely new cartridge, and ultimately — 30 years later — ended right back where it started.

The Bullet That Stopped One Inch Short

The forensic analysis revealed a devastating finding. Early in the fight, Agent Dove fired a 9mm 115gr Winchester Silvertip that struck Michael Platt in the right arm. The bullet entered Platt's torso through his arm, traversed his right lung, and stopped — penetrating approximately 6 to 7 inches into his chest.

The wound was ultimately non-survivable. But the bullet stopped roughly one to two inches short of Platt's heart.

Despite this fatal wound, Platt continued fighting. He killed both agents Grogan and Dove, wounded three more agents, and only died after absorbing a total of twelve gunshot wounds over the course of the battle.

The FBI concluded that if that 9mm Silvertip had penetrated just one more inch — reaching Platt's heart — he would have been incapacitated instantly, and agents Grogan and Dove might have survived.

The 10mm Experiment (1989–1997)

The FBI's Firearms Training Unit immediately began searching for a cartridge with deeper penetration. They settled on the 10mm Auto — a powerful round originally designed by Colonel Jeff Cooper and manufactured by Norma. The FBI ordered 9,500 Smith & Wesson Model 1076 pistols in 10mm, adopted in 1989.

There were two problems.

First, the full-power 10mm was brutal to shoot. Agents with smaller hands struggled to control the recoil, and qualification scores dropped. The FBI developed a reduced-power "10mm Lite" load running at approximately 950 fps — significantly softer than the original spec but still meeting their penetration requirements.

Second, the S&W 1076 was unreliable. Approximately half the pistols were sent back for rework. The gun was formally recalled in 1991 — just two years after adoption.

The FBI was stuck with a reduced-power load in a gun that didn't work. But they'd discovered something important: the downloaded 10mm performance they actually wanted didn't need a full-size 10mm case to achieve.

The .40 S&W Is Born (1990)

In January 1990, Smith & Wesson and Winchester jointly unveiled the .40 S&W at SHOT Show. The concept was elegant: take the FBI's reduced 10mm load and put it in a shorter case that fit in a medium-frame (9mm-size) pistol. Same ballistics, smaller package.

The .40 S&W duplicated the FBI's "10mm Lite" performance: a 180gr bullet at ~950 fps, delivering significantly more energy and penetration than the 9mm loads of the era. But it fit in existing 9mm-frame pistols with only minor modifications, maintaining a usable 15-round capacity (vs. 17 in 9mm).

The FBI formally adopted the Glock 22 in .40 S&W in May 1997, and nearly every major law enforcement agency in America followed. By the early 2000s, the .40 S&W was the dominant law enforcement cartridge in the United States.

The caliber wars appeared to be over. The .40 had won.

Why the FBI Switched Back to 9mm (2015)

Then modern bullet technology caught up.

Between 1986 and 2015, hollow point bullet design improved dramatically. Bonded jackets, controlled expansion petals, and engineered cavities transformed 9mm terminal performance. Loads like Federal HST, Speer Gold Dot, and Hornady Critical Duty consistently achieved 12–18 inches of penetration with reliable expansion through all FBI barrier tests — the same performance that had required .40 S&W a decade earlier.

In 2014, the FBI's Training Division published an internal study that essentially settled the debate. The key findings:

• Modern 9mm meets all FBI penetration and expansion standards. The terminal performance gap between 9mm and .40 S&W — the entire reason the .40 existed — had effectively closed.
• 9mm offers higher capacity. A Glock 17 holds 17 rounds of 9mm vs. 15 rounds of .40 in a Glock 22. Two extra rounds per magazine across every agent matters.
• 9mm improves qualification scores. Less recoil means faster, more accurate follow-up shots. Agents across the board scored higher with 9mm — especially agents with smaller hands.
• 9mm costs significantly less. Lower ammo costs mean agencies can afford more training rounds. More range time equals better shooters.

In 2015, the FBI transitioned back to 9mm, selecting the Glock 17 and Glock 19 as duty pistols. Their current duty ammunition is Hornady Critical Duty 9mm +P 135gr FlexLock — a load that didn't exist when the Miami shootout happened.

Nearly every major agency has since followed the FBI's lead. The .40 S&W — a cartridge literally invented because 9mm wasn't good enough — lost its reason to exist when 9mm became good enough.

The Full Timeline

What This Means for You

The FBI's 40-year journey teaches three practical lessons for anyone choosing defensive ammunition today:

1. Bullet Design Matters More Than Caliber

The entire reason the FBI left 9mm was that 1986-era hollow points didn't penetrate deeply enough. Modern 9mm loads like Federal HST 147gr, Speer Gold Dot 124gr +P, and Hornady Critical Duty 135gr +P consistently achieve 12–18 inches of penetration with reliable expansion — the same performance window the FBI requires. The bullet you load matters far more than the caliber you choose.

2. More Rounds = More Better

A 9mm pistol holds 2–3 more rounds per magazine than the same-size .40 S&W pistol. In a defensive situation, extra capacity is extra margin. The FBI decided those extra rounds were worth more than any marginal ballistic advantage .40 might still hold.

3. The .40 S&W Still Works — It Just Lost the Math

If you own a .40 S&W pistol, there's nothing wrong with it. The cartridge is ballistically effective. What changed isn't that .40 got worse — it's that 9mm got dramatically better. If you already own a .40, feed it quality hollow points and train with it. But if you're buying new, the industry consensus has shifted decisively to 9mm: cheaper to train with, more capacity, equally effective with modern ammo, and with a much wider selection of guns and loads available.