The FBI is Going 9mm: Here Comes the Science

Very interesting article posted over at on the adoption of 9mm by the FBI.

The FBI is Going 9mm: Here Comes the Science


UPDATE: There have been some questions about the origin of this FBI statement. As the word of the FBI’s solicitation for 9mm handguns became public, they were hit with a flood of questions from state and local agencies, many who carry .40, about the change. This statement was prepared the FBI Training Division to answer those questions and was intended for dissemination to law enforcement agencies. It was not classified Law Enforcement Sensitive and has spread to civilians. I have confirmed its origin and feel that its release poses no threat to law enforcement while providing enlightening science, paid for by taxpayer dollars, to the public.

After the Miami Shootout in 1986, the FBI invented modern ammunition testing and led the law-enforcement movement to .40 caliber. The FBI is very conservative, and has one of the best ballistics labs in the world.

With the amazing 21st-century advances in ammunition technology, many people have advocated a move back to 9mm. Recently, the FBI announced they were buying a new gun in 9mm. When the FBI makes a move like that, they have thought it through very thoroughly.

I respect the science and how hard it was for them to make this change. The FBI takes their leadership role in law enforcement very seriously. Below is their carefully crafted message, sent to other agencies, explaining their reasons.

FBI 9MM Justification

FBI Training Division: FBI Academy, Quantico, VA

Executive Summary of Justification for Law Enforcement Partners

· Caliber debates have existed in law enforcement for decades

· Most of what is “common knowledge” with ammunition and its effects on the human target are rooted in myth and folklore

· Projectiles are what ultimately wound our adversaries and the projectile needs to be the basis for the discussion on what “caliber” is best

· In all the major law enforcement calibers there exist projectiles which have a high likelihood of failing LEO’s in a shooting incident and there are projectiles which have a high ting incident likelihood of succeeding for LEOs in a shooting incident

· Handgun stopping power is simply a myth

· The single most important factor in effectively wounding a human target is to have penetration to a scientifically valid depth (FBI uses 12” – 18”)

· LEOs miss between 70 – 80 percent of the shots fired during a shooting incident

· Contemporary projectiles (since 2007) have dramatically increased the terminal effectiveness of many premium line law enforcement projectiles (emphasis on the 9mm Luger offerings)

· 9mm Luger now offers select projectiles which are, under identical testing conditions, I outperforming most of the premium line .40 S&W and .45 Auto projectiles tested by the FBI

· 9mm Luger offers higher magazine capacities, less recoil, lower cost (both in ammunition and wear on the weapons) and higher functional reliability rates (in FBI weapons)

· The majority of FBI shooters are both FASTER in shot strings fired and more ACCURATE with shooting a 9mm Luger vs shooting a .40 S&W (similar sized weapons)

· There is little to no noticeable difference in the wound tracks between premium line law Auto enforcement projectiles from 9mm Luger through the .45 Auto

· Given contemporary bullet construction, LEO’s can field (with proper bullet selection) 9mm Lugers with all of the terminal performance potential of any other law enforcement pistol caliber with none of the disadvantages present with the “larger” calibers

Justification for Law Enforcement Partners

Rarely in law enforcement does a topic stir a more passionate debate than the choice of handgun caliber made by a law enforcement organization. Many voice their opinions by repeating the old adage “bigger is better” while others have “heard of this one time” where a smaller caliber failed and a larger caliber “would have performed much better.” Some even subscribe to the belief that a caliber exists which will provide a “one shot stop.” It has been stated, “Decisions on ammunition selection are particularly difficult because many of the pertinent issues related to handguns and ammunition are firmly rooted in myth and folklore.” This still holds as true today as it did when originally stated 20 years ago.

Caliber, when considered alone, brings about a unique set of factors to consider such as magazine capacity for a given weapon size, ammunition availability, felt recoil, weight and cost. What is rarely discussed, but most relevant to the caliber debate is what projectile is being considered for use and its terminal performance potential.

One should never debate on a gun make or caliber alone. The projectile is what wounds and ultimately this is where the debate/discussion should focus. In each of the three most common law enforcement handgun calibers (9mm Luger, .40 Smith & Wesson and .45 AUTO) there are projectiles which have a high likelihood of failing law enforcement officers and in each of these three calibers there are projectiles which have a high likelihood of succeeding for law enforcement officers during a shooting incident. The choice of a service projectile must undergo intense scrutiny and scientific evaluation in order to select the best available option.

Understanding Handgun Caliber Terminal Ballistic Realities

Many so called “studies” have been performed and many analyses of statistical data have been undertaken regarding this issue. Studies simply involving shooting deaths are irrelevant since the goal of law enforcement is to stop a threat during a deadly force encounter as quickly as possible. Whether or not death occurs is of no consequence as long as the threat of death or serious injury to law enforcement personnel and innocent third parties is eliminated.

“The concept of immediate incapacitation is the only goal of any law enforcement shooting and is the underlying rationale for decisions regarding weapons, ammunition, calibers and training.”1

Studies of “stopping power” are irrelevant because no one has ever been able to define how much power, force, or kinetic energy, in and of itself, is required to effectively stop a violent and determined adversary quickly, and even the largest of handgun calibers are not capable of delivering such force. Handgun stopping power is simply a myth. Studies of so?called “one shot stops” being used as a tool to define the effectiveness of one handgun cartridge, as opposed to another, are irrelevant due to the inability to account for psychological influences and due to the lack of reporting specific shot placement.

In short, extensive studies have been done over the years to “prove” a certain cartridge is better than another by using grossly flawed methodology and or bias as a precursor to manipulating statistics. In order to have a meaningful understanding of handgun terminal ballistics, one must only deal with facts that are not in dispute within the medical community, i.e. medical realities, and those which are also generally accepted within law enforcement, i.e. tactical realities.

Medical Realities

Shots to the Central Nervous System (CNS) at the level of the cervical spine (neck) or above, are the only means to reliably cause immediate incapacitation. In this case, any of the calibers commonly used in law enforcement, regardless of expansion, would suffice for obvious reasons. Other than shots to the CNS, the most reliable means for affecting rapid incapacitation is by placing shots to large vital organs thus causing rapid blood loss. Simply stated, shot placement is the most critical component to achieving either method of incapacitation.

Wounding factors between rifle and handgun projectiles differ greatly due to the dramatic differences in velocity, which will be discussed in more detail herein. The wounding factors, in order of importance, are as follows:

A. Penetration:

A projectile must penetrate deeply enough into the body to reach the large vital organs, namely heart, lungs, aorta, vena cava and to a lesser extent liver and spleen, in order to cause rapid blood loss. It has long been established by expert medical professionals, experienced in evaluating gunshot wounds, that this equates to a range of penetration of 12?18 inches, depending on the size of the individual and the angle of the bullet path (e.g., through arm, shoulder, etc.). With modern properly designed, expanding handgun bullets, this objective is realized, albeit more consistently with some law enforcement projectiles than others. 1 Handgun Wounding Factors and Effectiveness: Firearms Training Unit, Ballistic Research Facility, 1989.

B. Permanent Cavity:

The extent to which a projectile expands determines the diameter of the permanent cavity which, simply put, is that tissue which is in direct contact with the projectile and is therefore destroyed. Coupled with the distance of the path of the projectile (penetration), the total permanent cavity is realized. Due to the elastic nature of most human tissue and the low velocity of handgun projectiles relative to rifle projectiles, it has long been established by medical professionals, experienced in evaluating gunshot wounds, that the damage along a wound path visible at autopsy or during surgery cannot be distinguished between the common handgun calibers used in law enforcement. That is to say an operating room surgeon or Medical Examiner cannot distinguish the difference between wounds caused by .35 to .45 caliber projectiles.

C. Temporary Cavity:

The temporary cavity is caused by tissue being stretched away from the permanent cavity. If the temporary cavity is produced rapidly enough in elastic tissues, the tensile strength of the tissue can be exceeded resulting in tearing of the tissue. This effect is seen with very high velocity projectiles such as in rifle calibers, but is not seen with handgun calibers. For the temporary cavity of most handgun projectiles to have an effect on wounding, the velocity of the projectile needs to exceed roughly 2,000 fps. At the lower velocities of handgun rounds, the temporary cavity is not produced with sufficient velocity to have any wounding effect; therefore any difference in temporary cavity noted between handgun calibers is irrelevant. “In order to cause significant injuries to a structure, a pistol bullet must strike that structure directly.”2 2 DiMaio, V.J.M.: Gunshot Wounds, Elsevier Science Publishing Company, New York, NY, 1987, page 42.

D. Fragmentation:

Fragmentation can be defined as “projectile pieces or secondary fragments of bone which are impelled outward from the permanent cavity and may sever muscle tissues, blood vessels, etc., apart from the permanent cavity”3. Fragmentation does not reliably occur in soft tissue handgun wounds due to the low velocities of handgun bullets. When fragmentation does occur, fragments are usually found within one centimeter (.39”) of the permanent cavity.4 Due to the fact that most modern premium law enforcement ammunition now commonly uses bonded projectiles (copper jacket bonded to lead core), the likelihood of fragmentation is very low. For these reasons, wounding effects secondary to any handgun caliber bullet fragmentation are considered inconsequential. 3 Fackler, M.L., Malinowski, J.A.: “The Wound Profile: A Visual Method for Quantifying Gunshot Wound Components”, Journal of Trauma 25: 522?529, 1958. 4 Handgun Wounding Factors and Effectiveness: Firearms Training Unit, Ballistic Research Facility, 1989.


Any discussion of stopping armed adversaries with a handgun has to include the psychological state of the adversary. Psychological factors are probably the most important relative to achieving rapid incapacitation from a gunshot wound to the torso.5 First and foremost, the psychological effects of being shot can never be counted on to stop an individual from continuing conscious voluntary action. Those who do stop commonly do so because they decide to, not because they have to.

The effects of pain are often delayed due to survival patterns secondary to “fight or flight” reactions within the body, drug/alcohol influences and in the case of extreme anger or aggression, pain can simply be ignored. Those subjects who decide to stop immediately after being shot in the torso do so commonly because they know they have been shot and are afraid of injury or death, regardless of caliber, velocity, or bullet design. It should also be noted that psychological factors can be a leading cause of incapacitation failures and as such, proper shot placement, adequate penetration, and multiple shots on target cannot be over emphasized. 5 Ibid.

Tactical Realities

Shot placement is paramount and law enforcement officers on average strike an adversary with only 20 – 30 percent of the shots fired during a shooting incident. Given the reality that shot placement is paramount (and difficult to achieve given the myriad of variables present in a deadly force encounter) in obtaining effective incapacitation, the caliber used must maximize the likelihood of hitting vital organs. Typical law enforcement shootings result in only one or two solid torso hits on the adversary. This requires that any projectile which strikes the torso has as high a probability as possible of penetrating deeply enough to disrupt a vital organ.

The Ballistic Research Facility has conducted a test which compares similar sized Glock pistols in both .40 S&W and 9mm calibers, to determine if more accurate and faster hits are achievable with one versus the other. To date, the majority of the study participants have shot more quickly and more accurately with 9mm caliber Glock pistols. The 9mm provides struggling shooters the best chance of success while improving the speed and accuracy of the most skilled shooters.


While some law enforcement agencies have transitioned to larger calibers from the 9mm Luger in recent years, they do so at the expense of reduced magazine capacity, more felt recoil, and given adequate projectile selection, no discernible increase in terminal performance.

Other law enforcement organizations seem to be making the move back to 9mm Luger taking advantage of the new technologies which are being applied to 9mm Luger projectiles. These organizations are providing their armed personnel the best chance of surviving a deadly force encounter since they can expect faster and more accurate shot strings, higher magazine capacities (similar sized weapons) and all of the terminal performance which can be expected from any law enforcement caliber projectile.

Given the above realities and the fact that numerous ammunition manufacturers now make 9mm Luger service ammunition with outstanding premium line law enforcement projectiles, the move to 9mm Luger can now be viewed as a decided advantage for our armed law enforcement personnel.

This information was published by Loose Rounds on September 21, 2014.


The FBI is Going 9mm: Here Comes the Science — 22 Comments


  1. The US Marine Corps. is going BACK to the .45 ACP because of the ineffectiveness of the 9mm. HMMMMMM, and who do you think is right?
    I don’t quite agree with AC that it is the size of women agents hands, I believe it is because women can’t handle the heavier recoil of the .40 cal, or the .45ACP. The pussification of America continues under the umbrella of political correctness. As a result, the lives of FBI agents will be in greater danger as they will be using less effective fire power. The chance for collateral damage will be greater because of more shots needing to be fired to put down the perp. A lowering of the standards to keep a certain percentage of women employed as field agents with the FBI.

    • Having not been in the military I can’t speak with authority, but…. my knowledge on the subject is that the military is restricted to ball ammunition. If that’s the case then yes, a 45 would be more effective than the 9mm. However, that is not what this report was referring to. It states quite clearly that the new bullet technology makes the 9mm nearly as effective as the 40 and possibly the 45. I carry the 9mm every day for the reasons stated. 9mm +p ammo with a quality hollow point is ballistically very similar to a 40 with a quality hollow point. As the article states, most important is hitting the target, and even men may be able to do so with the lessor recoil of the 9mm. As one of the other commentors stated, “no one wants to let me shoot them with the 9mm”. I don’t want to ever be hit by one either.

      • Officially they are restrcited to FMJ ball ammo. Unoficially speaking many special operations teams have been known to procure and use thier own JHP ammo on several occasions.

    • The Marine Corps is NOT going back to .45acp. One small part of the Marine Corps uses 1911 in .45acp, that’s it. And, BTW< they also just authorized the use of Glock 19s by this same unit.

      Your comments on "pussification" are frankly just plain ignorant as hell. None of that is in play here.

      The fact is that the issued FBI 9mm duty load equals their .40 duty load in wound ballistics, and EXCEEDS their issued .45acp duty ammo.

      Why would one chose a caliber that is both more expensive, recoils more, and causes more weapons maintenance issues, when you don't have to?

      BTW, real world reports from guys who can shoot are that the 9mm works as well as the .40 and .45, even with ball ammo.

      In closing, "What does the one of the world's leading experts on gunshot wounds, the guy who quite literally wrote the book on gunshot wounds in fact, have to say on the subject?" I'm glad you asked, I'll leave this right here;

      “…there is no appreciable difference in the effectiveness of the 9 mm and the .45 ACP cartridges.”
      Vincent J. M. Di Maio, GUNSHOT WOUNDS: Practical Aspects of Firearms, Ballistics, and Forensic Techniques SECOND EDITION, Page 150.

  2. First, How about we spend more time on the range to improve the on target percentage. Second, some of the data they are quoting is in direct opposition to the U.S. Military research and the reason they are dumping their 9mm in favor of great stopping power. I have to believe that the U.S. Army has had significantly more actual live fire test subject in the last 20 years to be able to identify the short comings of the 9mm rounds. Lastly make a stand and back it up .38 to 9mm to 10mm, to the .40 cal now back to 9mm all in a 20 year span, on who’s dime ?

  3. Most all of the points that were highlighted in this article is exactly why I cary a 9mm handgun today. The fact that I have 20 rounds of ammo in one magazine, am able to make much more accurate shots, and have less expensive & readily available ammo available makes the 9mm my weapon of choice for every day carry. It is nice to see that there is now some sound science to back up what I have felt to be true and have defended for so long.

  4. The 9mm is a good round. But it is true, more rounds to stop the threat and it’s cheaper than dirt. It has been proven time and time again in Iraq and Afghanistan. The 9mm is accurate, but not as proficient when it comes to stoping a threat. The Marine Corps armories are slowly filling up with .45 cal. At least what I’ve seen in the LE and Security sections. It’s only a matter of time, when the Marine Corps and the rest of the military branches, get rid of the M9 and turn it over to the FBI or who ever wants it.

  5. As a former federal Agent — Please note the studies they use are tabbed 1987 (2 DiMaio, V.J.M) AND 3 (Fackler, M.L., Malinowski, J.A) 1989…. HUMMMMMM with all that FBI research you cant find a study to back your information within the last 30 years… information concluded before the 9mm controversy of the 90s. I have seen too many suspects in a ER with center mass shots form a 9mm still talking and breathing to convince me of same. Remember all the studies in 2000 in kinetic energy transfer and tissue damage equal stopping power? The phrase was Terminal Velocity….

    Please look at Wikipedia for their comments on terminal velocity- starting with the below- Then Call BS on the study…

    Example: A .44 Remington Magnum with a 240-grain (0.016 kg) jacketed bullet is fired at 1,180 feet per second (360 m/s)[2] at a 170-pound (77 kg) target. What velocity is imparted to the target (assume the bullet remains embedded in the target and thus practically loses all its velocity)?

    Let mb and vb stand for the mass and velocity of the bullet, the latter just before hitting the target, and let mt and vt stand for the mass and velocity of the target after being hit. Conservation of momentum requires

    mbvb = mtvt.
    Solving for the target’s velocity gives

    vt = mbvb / mt = 0.016 kg × 360 m/s / 77 kg = 0.07 m/s = 0.16 mph.
    This example shows the target barely moves at all.

    From Eq. 1 we can write for the velocity of the gun/shooter: V = mv/M. This shows that despite the high velocity of the bullet, the small bullet-mass to shooter-mass ratio results in a low recoil velocity (V) although the force and momentum are equal.

    Kinetic energy[edit]
    However, the smaller mass of the bullet, compared that of the gun-shooter system, allows significantly more kinetic energy to be imparted to the bullet than to the shooter.

    • Reference wikipedia to call BS on the story. LOL

      Federal Agent = TSA Agent?

      There have been people who have been shot multiple times from 7.62×51 and lived. Carry what you want, and like I said for all the 9mm haters I have yet to meet anyone which wouldn’t mind being shot with one.

  6. Hmmmm well I guess the next logical step is issuing so called ” Saturday Night Specials” because they are smaller, easier to carry along with more ammo, quicker to put into use, etc. etc. etc. add nauseum. You know, like how much better Obama care is going to be. Really………give us all a break…….Please.

  7. No such thing as stopping power. How about we look at history, say the Philippine-American War. The weapon then was a 38 long colt. The drugged up Moros were not evening slowing them down. So the Army in it wisdom went back to using 45 colts (long Colt) Problem solved. Then the army went searching for a semi auto replacement. The 45ACP. Now all the modern updates in ammunition haven’t been limited to the 9mm they have also advanced in 45ACP. LEOs miss between 70 – 80 percent of the shots fired during a shooting incident, this statement is the key to all of it. You will find this is probably true weather its a 22 or 500. So the trick for the LE is to out last the adversary as far as ammunition. In this the 9mm would be about the best, since 380 doesn’t do well against car doors. The big key is to dump as much Kinetic energy into the target as possible. In a measure of energy loss between the 9mm and 45ACP into a target it would be found the 45 dumps more. Here is a real good fact for you 7.62X25 is an excellent penetrator. It blows right through its target even many body armors. It has a high muzzle energy. Problem it blows thru so fast and dumps little energy to target. So there is a real life case for you. Big bullet does more real damage than small one. No using mathematics to show the idea but real data that shows the real.

    • The thing with the Moros is pure mythology, they didn’t drop any faster when shot with .45s either.

      Kinetic energy means exactly nothing when discussing wound ballistics, and there is no such things as “energy dump.

      The dynamics of LE gunfights is commonly misunderstood. In many cases the officer shooting, and missing a bunch, has been wounded already. This is a bit more complicated of a shooting problem than detractors would even care to admit, let alone acknowledge.

      • I work for a major southern cal LE and we issue 9mm but are authorized the 45 acp also, we issue Winchester SXT, great ammo but as in every gunfight shot placement is everything. For us the 9 has a better stopping history due to good solid hits center mass. The guys with the 45 have a tendency not to train on their own dime. I carried a 45 for several years but couldn’t shoot it as well. So I switched back to the 9(also carried a 38 my first 5 years). Accurate follow up shots are the next thing the 9 out performs the 40/45’s. Oh by the way for all you guys training and never been in a gunfight, a two way range will change everything as far as accuracy goes. So when I hear this talk about 30% hits, go take one these classes where they use simunitions and by the way use a tshirt only so you get the pain and welts from the potential of getting hit. Tell me how you did. JMHO. Keep training!!

  8. He all,
    Just figured I would throw in my 2 cents worth…The most important factor in any firefight is shot placement…and that can be achieved with any caliber but it relies on the shooter spending the time needed at the range to create and maintain their confidence and comfort levels with their weapon of choice. A 22lr placed effectively will be just as capable at eliminating a threat as a 45ACP…Why you ask? It’s quite simple…accuracy, no recoil, increased magazine capacities, and more accurate rapid follow up shots…and of course you aim for neck and above to kill, or knees and elbows for non-lethal incapacitations. I prefer carrying my 40 but am just as capable with a 22lr, 9mm, or 45acp. The key is in understanding the limits and advantages(real or psychological) and knowing that you can hit your target.

  9. statistics don’t lie i guess…it will be a lot easier for me to carry a 9 mm into bear country rather than to lug my .454…why didn’t someone tell me before? did anyone tell law enforcement that 9mm will penetrate windshield glass and car doors just as well as .40, .357 smith or sig, or .45?

Leave a Reply

Your email address will not be published.