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What Caliber Gun Does the FBI Use?


For decades, the FBI’s stance was to go big or go home when it came to the calibers of their handguns.  That mentality has changed recently, thanks to engineering and science.  

 An incident in Miami that occurred back in 1986  made the FBI realize that they needed something a little more powerful than the 9mm. Their answer was to adopt the 10mm caliber pistol. When this did not pan out, they switched to the .40 S&W (Smith and Wesson). 

The .40 (S&W) would become the standard FBI issued handgun. Other law enforcement agents carry bureau issued .40 S&W. for years after this point as well.

So which caliber gun does the FBI use today? In the early to mid-2010s the FBI shocked many by switching back to the 9mm as the FBI sidearm.

Yes, you heard that right. The caliber the FBI said was not powerful enough, was the one they went back to. Why go back now after all those years? The answer is simple. Today’s 9 mm is vastly more superior than the 9 mm from the ’80s.      

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FBI 9MM Justification

With the bombshell news of going back to the 9mm now public, the FBI was inundated by the public and other law enforcement agencies on why they made the decision to switch back. So in 2014, after a Freedom of Information Act (FOIA) request about the change, the FBI presented some compelling reasons for switching back to the 9 mm. They included the following:

  • Stopping power is a myth. In fact, the FBI states that most “common knowledge” of ammunition and how it affects humans are myths.
  • Over the past few decades, the 9 mm has had many engineering improvements. The FBI began to notice that some 9mm rounds were outperforming some of the .40 S&W and .45 auto rounds in terminal performance back in 2007.
  • The FBI also noted the 9mm has a higher magazine capacity, has less felt recoil, lower operating cost, and are more reliable than larger caliber pistols.
  • It was additionally stated in the Freedom of Information Act (FOIA) that the majority of FBI agents are more accurate and faster with the 9 mm as compared to the .40 S&W and .45 auto.

Justification for Law Enforcement Partners

The FBI also gave more details specifically geared to other law enforcement agencies on why they switched.   

They dismiss the notion that bigger is always better as nothing more than a myth and that no caliber out there today can be defined as “one-stop shot”.

The FBI stated the projectile, not the gun or caliber, should be at the center of the discussion about which caliber to use. They also stressed that to pick the correct caliber with the right projectile, extensive scientific research must be performed. Research that the FBI has heavily invested resources into.

Per the FBI’s research, the most critical trait of a caliber is its ability to wound a human. The cricital measurement a bullet needs to penetrate into soft tissue is between 12-18 inches during terminal performance testing. 

Understanding Handgun Caliber Terminal Ballistic Realities

When deciding to go back to the 9 mm, the FBI explained that all three of the most common calibers used by law enforcement can immediately incapacitate a human, which is the primary goal of any law agent when they must fire their weapon.

The FBI Reason to Switch to Back to the 9 mm Summary

Some significant factors that lead to the switch to 9 mm were that both the larger caliber .40 S&W and .45 auto have less magazine capacity, more felt recoil, and are more costly to use than the 9 mm.   (I wonder if FBI tried using the Glock 19 in any of these test…)

However, the most critical factor was that many 9 mm rounds performed better than the larger calibers in the FBI’s testing.


If you are like me when you first heard that the FBI was going back to the 9 mm, you were shocked. Nevertheless, after viewing the FBI reasoning for the switch, you can see they made the right call to switch.

So next time you are in the market for a new pistol, remember this infomration before deciding on which caliber to purchase and which IWB holster to use with it

But what gun Whether you like the 9 mm or not, the one thing we can agree upon is that the FBI did their homework before switching back to the 9 mm.   If you want to learn some more cool tips, tricks, and random trivia you may never use check out all our trip,tricks, and how-tos. Until next time.

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