FBI 9MM Justification, FBI Training Division

This has been making its way around the Internet and we thought it was worth sharing.

May 6, 2014

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 LEO’s 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”)
  • LEO’s 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.


    79 Responses to “FBI 9MM Justification, FBI Training Division”

    1. james says:

      complete nonsense. You do knew where the term “double tap” came from and why?

      • Pogie bait says:

        Sounds like someone didn’t read the article…

      • Jack says:

        I heard one time….

      • bloke_from_ohio says:

        Anything worth shooting once is worth shooting twice, or three times, or until it stops being a threat.

      • The FBI study makes several good points; no I didn’t drink the Kool-Aid.

        The biggest problem identified is not which, bullet, caliber or gun is better for Law Enforcement use but the number of rounds fired in a life threatening conflict. The study identified that Law Enforcement Officers failed to hit a threat in the torso 70-80 percent. To me that clearly identified that the FBI knows that the police firearms training across the country is poor. Why doesn’t the FBI study that, come up with a plan to improve the perishable skills, make training suggestions and improve the training. I know the facts are that budgets are tight and one of the first items cut in a law enforcement agency is the training budget. The availability of time and practice rounds in a major city like San Jose, CA with a department of 900 sworn members is a joke; practice time, training and rounds are nonexistent.

        If the average person failed at work 70-80 percent of the time we would get fired! Why is this acceptable when an officer is firing their duty weapon in the defense of their life or the defense of another person’s life that 70-80% fail is viewed as industry standard by the FBI. I know extreme stress and every incident is unique in a life-threatening encounter. In other words with 10 rounds being fired by police 7 to 8 rounds in a police action are flying towards innocent by-standers instead of hitting the life threatening bad guy/girl.

        Tactics and training need to change, and I’m sorry but the money needs to stay in the training budget so individual officers can do some practice when the agencies fail to. The training needs to be modernized and up-dated again it cost money. But management looks at police shootings as a rare occurrence and thankfully they are as a whole but 80% fail is unacceptable. Litigation is not cheaper then training and 70-80% failure rate is not acceptable or industry standard by the average sworn member in law enforcement.

        The USSS use to qualify on a monthly occurrence with unlimited practice rounds, many states only require that PD’s qualify 2 times a year and the qualification requirements are less then stressful. It comes down to the lack of training and budget.

        Have a nice day.

        • Bryan says:

          Well said 70 percent fail is not acceptable

        • PeaceSouljer says:

          The use of firearms to incapacitate a threatening individual or suspect is really no longer practical. You see videos [] where a LEO will fire several clips at and into a suspect, and because their system is flooded with adrenalin or other substances, they just keep coming! The LEO of this country put their lives on the line every day, and with oppressive regulations and lack of training time/facilities, their marksmanship rate will remain dismal.A new strategy needs to be created where a device creates a reaction similar to a Taser – one that overloads the nervous system and causes non-lethal incapacitation that can be deployed quickly and does not require precise aiming..

    2. Felix says:

      Wow,I bet this will turn out into a professional and civilised debate I would really like to attend….. but sadly I now have to drive to our customs agency to pick up a set of body armor….

    3. Russ says:

      Excellent article. Do not know what James was reading.
      Double tap is just what it sounds like. Two fast shots in succession. First shot is referencing the sights the second shot is not. This is more of an old school training paradigm. Now the focus is on a “controlled pair” This is where you reference the sights with each shot. Speed is not so much of a compromise here as your hits on target are better with increased distance and less likely to hit innocent people.

      It boils down to that old argument. Shot placement is better than caliber. If I am hit in the CNS with a 22 and hit in the calf with a 45 the 22 is going to stop me period.

      Should check out This guy has done an excellent job of comparing different bullets. Interesting to note that for instance Hornady Critical Duty does not perform as well as the critical defense for most of the needs I would find myself in. Critical Duty must pass the barrier tests so there is a compromise in the bullet design. I will most likely not need to shoot through most of these barriers so I need a bullet that will get max expansion and penetration through the gun I choose to carry. Barrel size can significantly change the performance. Worth checking out the data for yourself.

    4. Dumb Ass Marine says:

      Practice does not make perfect, practice makes bad habit. Perfect practice make perfect.

      Russ hit the nail on the head. Shot placement, shot placement, shot placement. Which is only achieved by perfect practice. All else is bullshit.

      The FBI discovered this back in the late 1980’s after a shoot out with two bank robbers in Miami that had two of their own killed and several of their own critically shot. The killer was clinically dead from the second round fired in the engagement. His heart was in effect blown apart by a 9 mm through and through. He was also shot many multiple times (forgot how many times). Five minutes later, after two dead FBI and several FBI shot, he was killed by a shot to the back of his head, which induced flaccid paralysis. No drugs were found in his body.

      The FBI did a study. Long and short, CNS first, then head shot, then as a last resort finally as many shots into torso as possible to bleed out the target as fast as possible.

      Russ is right. FBI is right. Do not matter the size of the bullet. Shot placement is the only thing that matters.

      • Evan says:

        “Practice does not make perfect, practice makes bad habit. Perfect practice make perfect.”

        Something that was preached to me by my dad since I started shooting as a child. Brings back memories.

      • Homeslice says:

        What this guy said:

        SHOT PLACEMENT people.

        It’s not your caliber, it’s your accuracy.

    5. FormerSFMedic says:

      One thing readers need to understand when examining any FBI ballistics studies is that they are very biased. Nothing published in this write up is necessarily wrong. It just comes from a biased point of view.

      • Jack says:

        Excellent point. Everyone has an agenda. It would be great to think they provided an honest and accurate study but I wouldn’t be surprised to find out if there was another factor besides handgun performance was behind their switch.

        • SSD says:

          I’m hearing qualification. It’s easier to qualify with 9mm.

          • BAP45 says:

            Very True. I have an old 1911 in .45 and I love it but would I issue it en mass? No.

            Plus as they said there are some really sweet new rounds for 9mm now.

          • Bman says:

            Easier to shoot on the range still means easier to shoot under stress. I’ve always been a 40 and 45 fan but bought a 9mm to do contract security work which state regs mandate 9mm. For whatever reason, I can shoot the 9 far better than any other caliber I’ve shot.

      • Michael says:

        Doesn’t really matter if they’re biased if they’re right.

        More ammo, faster par times, less recoil, cheaper training costs, less recycles/training dropouts at Quantico for failing firearms, and almost identical wound patterns?

        Sounds just about perfect.

        • FormerSFMedic says:

          I’m not referring to the unequivocal facts. I’m referring to the theoretical conclusions that are sometimes expressed by the authors in these FBI ballistics studies. The bias comes from a specific event in FBI history that I’m sure everyone here is familiar with.

    6. John says:

      With all the talk about advanced technology in bullets, I wonder what ammo they’ve landed on.

      Didn’t they formerly use Speer gold dot? Maybe I’m thinking of my local agency…

    7. Ab5olut3zero says:

      Respectfully, by their logic then we should all be deer hunting with 9mm. Also, did anyone else notice they kept using the phrase “premium projectile” over and over? Premium usually refers to cost- meaning higher. So, what does that mean for the average consumer? It’s great if you’re getting your rounds issued and you don’t have to pay for them.

      Also, there are tons of anecdotal evidence of double taps to the chest in combat conditions not being sufficient.

      • Jack says:

        9mm for deer hunting? That’s your take away from this? You need the FBI to tell you which bullets to buy?

        Anecdotal evidence? Did you read the article?

        “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.””

      • Jeremy says:

        There logic clearly states to use a rifle if able. But if you have to use a pistol, the size of the bullet is not as important as shot placement.

      • ctopher says:

        “So, what does that mean for the average consumer?”

        Nothing special. I shoot bulk Wolf 9mm 115 grain FMJ out of my Glocks. I buy a thousand rounds at a time off the internet ($220 right now) to practice with.

        I then have 300 rounds (enough to fill 8 mags) of Hornady 9mm 135 grain Critical Duty HP for when I am not practicing. I have shot enough of it in the past to know I don’t have any cycling issues. The 300 rounds will hopefully never be touched.

      • Justin says:

        I don’t know about you but if it costs me $30 dollars in ammo to save my life, it’s $30 well spent.

    8. Steve says:

      This is only a summary of the full Ballistics Research Facility presentation. The full presentation covers the FBI testing protocol, its origin, and how rounds are scored. It also covers the 1986 Miami shooting and the performance of the 9mm service round in that event. From the full presentation you see how the FBI decided on 10mm and later .40SW based upon the performance of the 1986 era 9mm.

      • SSD says:

        Thanks for the clarification.

      • Jeremy says:

        Is the full Ballistics Research Facility presentation available anywhere? It sounds like an interesting read.

      • Dumb Ass Marine says:

        Actually, the 10 mm was a knee jerk reaction to what happened in Miami. Then they found that the 10 mm literally broke their S&W pistols, so they went to the .40 (there were some rumors that certain agents could not qualify with the 10 mm).

        Then the study was performed. What they did was shoot cadavers with everything from a .22 LR to a 454 Cahsul (largest hang gun at the time) They results shocked the scientists. Hollywood was busted…bodies do not, in fact fly 20′ through the air when shot. The delta movement difference that the cadaver moved between the .22 LR and the 454 Cahsul (I am probably spelling that wrong, so forgive me) was less than 1.5″.

        So there went the bigger is better theory. Then the FBI studied physiology…what the bullet does to humans. The results were such that you needed to induce flaccid paralysis (turn the body off), which is caused, in the simplest terms, causing so much pain that the brain shuts down and has to reboot. This is best facilitated by hitting the CNS. Death is usually a byproduct of shooting the CNS. If you can’t do that, put the shot into the head. This induces lots of pain, causing the brain to shut down, but the body will still ‘twitch’. Last resort, put as many rounds, as in holes, to cause the body to bleed out. The problem with that was a motivated target, can still do damage for up to 5 minutes before the lack of oxygen causes loss of consciousness. Case in point, what happened in Miami.

        As to 9 mm, 40 cal or 45. Perfect practice, perfect practice, perfect practice resolves which weapon to use with regards to recoil and such. Personally, when I heavy carry, I use the FNP-45. The weapon is designed to recoil like a 9 mm. (Plus I am old enough to have initially trained on the 45 more years ago than I would like to admit).

        Overall a great thought provoking article and great discussion.

    9. AbnMedOps says:

      This document looks like a draft version, based upon the typos, incorrect dates of the Fackler citation, etc.

      Author does have a bit of a point, but I would argue that argue that shot placement AND bullet performance AND a bigger bullet is more likely to be a more-winning combination. However, also bear in mind that FBI and other government entities has a different set of priorities: first and foremost, they must satisfy certain political imperatives, to include “qualifying” and graduating X percent of certain demographic/”diversity goals”, which may include very small persons (sometimes female), very mechanically inept persons, and persons who do not have the aptitudes, attitudes, values, and mindset of the American “gun culture”. So the agencies limp them through some form of training with a 9mm (they’de use .22’s if they thought they could get away with it), and hope they don’t shoot themselves or anyone important before the next “qualification” session.

      • Bob says:

        Sadly, this is closer to the truth than most will admit.

      • Chuck says:

        Like all things in life, it’s a balance of speed, size, and how well you can use it.

      • Loop says:

        Sounds like someone is harboring a bit of jealousy because they didn’t make it through the FBI application process.

        • mb says:

          you mean promotion process

        • AbnMedOps says:

          Huh? Not me…I had never given any serious thought to applying to FBI, although two of my peers did leave the Army and go FBI. But I will conceed that I probably would not have made it through the application process – I don’t have a JD or CPA. And probably don’t fit their template in a number of ways. All due respect, but of the things I could get jealous over, an FBI career isn’t one of them.

    10. John Smith says:

      If this is true and I have no reason to think it isn’t, the real practical take away is: More rounds down range for cops.

      Caliber being rendered a less important discussion by technology- lets get that hit ratio up….

    11. Angry Misha says:

      While the article states that; “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 no concrete evidence that a caliber change will impact the fact that; ” LEO’s miss between 70 – 80 percent of the shots fired during a shooting incident”. Remember, the data is gleaned from the latter comment is from ALL kinetic engagements and not based on a specific caliber. Essentially, regardless of the caliber used (9mm, .357 Sig, .40 S&W or .45 ACP) the hit probability will be the same.

      While a lighter recoil may increase hits during TRAINING when there is no threat, the various physiological factors of a deadly force situation will still impart a 70 to 80 percent miss ratio.

      So, if we err on the high side (80%) and use the current Glock 22 as our base (15 in the mag one in the pipe) that means right now in a kinetic engagement, there are 13 rounds “looking for a home”.

      Using the same logic applied to the Glock 17 (17 in the mag one in the pipe) there are now 15 rounds “looking for a home”.

      The key to putting down an opponent as mentioned here is “shot placement” coupled with realistic training. Unfortunately, there are very few “gun fighters” left in the LEO community. When I conduct training with LEO’s, I try and reinforce this by talking about “The Bridge”. The most dangerous adversary you will encounter in a gunfight is someone who has already killed someone and crossed “The Bridge” which is why realistic training is important. If you can’t rapidly and accurately impart a CNS wound, it doesn’t matter what caliber you are using.

      I think the key take away to this that it is attributed to cost.

    12. ctopher says:

      This is nothing new from the FBI. This has been out there for some time..

      It is a great read and the reason I stuck to the 9mm.

    13. BAP45 says:

      I know this is anecdotal and not a quantifiable or scientific study but in the past when I would be at a match and we were shooting steel poppers I remember noticing the 9mm having more trouble knocking them down more than the .45s. Wouldn’t that count for something when doing comparisons?

      I know it has nothing to do with penetration and wound cavity etc etc but those stages just always stick out in my mind.

      • Russ says:

        Gun talk TV had a recent episode about bullets and penetration. They stacked up two bags of quickcrete on a table. Fired 9 mm , 45 ACP and a large rifle caliber. The 9 and 45 were similar. No movement of the bags so the energy transferred is in the size of the wound. Bigger hole more bleeding. Faster bullet deeper penetration. Rifle caliber will provide more energy transfer and when its over 2000 ft per second you get secondary trauma from hydrostatic shock. The rifle showed some minor movement of the bags.

        The knockdown power is a myth. Doubtful anything short of a large rifle will knock someone down. Even then the energy transferred into and through so no pushing action on the target like you see in rigid steel. Now if you are wearing body armor that may change things up a little.

      • Chris K. says:

        It comes down to penetration. Yes a 45ACP has more energy/momentum, but it does not necessarily cut through into vital organs like a 9mm going almost twice as fast.

        • KP says:

          When you’re talking about human targets, a .45 will still carry enough energy to get from one side to the next. It’ll at the very least penetrate the two or so inches from outerwear to the pericardial sack. It’s been said that the end result of a shooting will show little effective difference between a .45 and a 9mm which goes both ways – a 9mm will leave a hole that’s largely indistinguishable (in autopsy) from a .45, and .45 isn’t going to hit like a bouncy ball next to 9mm’s needle.

          I like this overall trend back to 9mm (or more rather, a general increase in accepting 9mm over .45) as you need to justify why 9mm might be more effective than a larger bullet. I like to think that more people are critically thinking about their choice in bullet.

      • bloke_from_ohio says:

        A bullet fired with enough energy to literally knock down a person like it knocks down a plate would also knock down the shooter with the recoil. The laws of physics apply. You cannot expect your traget to be imparted with more energy than you the shooter are. In fact given the differences in how flesh reacts vs how hard steel reacts to being struck with a bullet you would need even more energy than just enough to knock down the shooter with recoil. Poeple are squishy and the bullet won’t just smack into the person and push on them like it does with your plate. Unless the bullets are accelerated after they leave the barrel by a rocket or something it cannot happen.

        That said, a .45 should knock a plate down with more force than a 9mm. The .45 has more recoil so by the equal and oposite reaction principal the round should smack the plate harder. But people are a lot heavier than a plate.

      • majrod says:

        BAP45 – 9mm fans will tell you you aren’t hitting the plate in the right place. It’s all about shot placement.

        I agree but sometimes the bad guy isn’t obliging you so you shoot what’s visible.

      • Mac says:

        Were the shooters with 9mm shooting factory loads, or low recoil handloads?

        Just a thought that may have something to do with what you saw at a match.

      • Dave says:

        Since we’re talking physics, lets try this on for size. No collision is perfectly elastic of the ideal sort in which energy is perfectly conserved. However, even in an inelastic collision, momentum is conserved. So, when we start talking about pushing plates and knocking them down, momentum is the point on consideration. Momentum does not share kinetic energy’s velocity bias, it’s just a straight forward mass * velocity. The ratio of bullet weight in a 230 gr .45 ACP to a 124 Grain 9mm is 1.98. If we set the 9mm velocity such that it will yield equivalent muzzle energy (i.e. that ratio of the 9mm to .45 velocity squared = 1.98), that yields a velocity ratio of 1.41 or a velocity of roughly 1200 fps to a velocity of 850 fps (9mm to .45).

        So, we can expect the .45 ACP to have roughly 40% more momentum in this particular comparison where the kinetic energy at the muzzle is the same. You can, therefor, expect the .45 to be more effective on plates and less sensitive to how the plate rack is configured, friction between the plate and the rack, angle of impact, shot placement on the plate, etc.

        • BAP45 says:

          bloke_from_ohio I wasn’t saying that it would knock down a person, thats just foolish, And I realize that steel is not flesh but I was wondering if that different energy wouldn’t have some kind of different effect on wounds/targets whatever. Just curious if it had been measured or considered. (I picture that punching thing that the russian guy in rocky was punching haha)

          Before people freak out and think I’m trying to beat up on 9mm I’m not, I have a 9mm and I love it, just curious if that was in the studies.

          • Dave says:


            Referencing physics, a cartridges ability to do “work” (create wounds) is a product of its energy and the method by which that energy is transfered. The .40 S&W and .357 SIG produce slightly more energy than the .45 ACP and 9×19. The 10mm and .357 Magnum produce more energy still.

            However, the main concern is the delivery of said energy to the target. This is where projectile performance is king, more than the wounding potential represented by the KE of a given projo. The frontal area and shape of the bullet significantly impact energy transfer. All your standard pistol calibers can, under the right circumstances, shoot through a person. The energy used to break skin on the far side of the target and carry the projectile out of the body is wasted.

            The key to a high performing hollow point is consistent bullet upset and predictable energy transfer. To maximize wounding potential, and expended all the projectiles energy is the goal. How that energy is expended, the way the bullet does work, whether it’s fragmentation, rapid expansion or delayed expansion, are more important to the overall wound creation than just the starting KE number.

            As an example, a .44 Rem. Mag. with a 300 grain Keith style SWC at 1350 fos is an excellant hunting combination capable of taking big game very effectively. It is a TERRIBLE combination for use on humans – that SWC will punch a nice neat hole straight through your target and the limited energy transfer will produce lack luster terminal performance. It will, of course, drop a steel plate or clean a rack of bowling pins in a way that makes 1911 shooters jealous.

            Ultimately, the wounding of a bullet design transfering similar amounts of energy in similar fashion ends up being…well, similar, regardless of how wide the bullet was when it left the muzzle. There are so many other factors – marksmanship, reliability, to name two – that are significantly more important than the relatively small theoretical difference in handgun wounding potential.

    14. Chris M says:

      Thanks for posting. Good article to read up on.

    15. Roach says:

      A point of view is not “bias,” it’s an opinion based on evidence. There is a factual based question involved here: What’s the best caliber for self defense based on all the manifold considerations and evidence available.

      Incidentally, I recently switched from 40 to 9mm for many of the reasons cited by FBI. I get two extra rounds, and my shot strings are faster and more accurate and it’s less exhausting to shoot. I think modern 9mm HP is the way to go.

      As for the recoil theory above: it’s not just a question of force but surface area. Otherwise, under this theory, the gun should rip through your hand the way the bullet does the target. It doesn’t. The energy in recoil is taken up by heat, the weight of gun, the weight of your body, and spread over the large surface area of your hand and it’s interaction with the gun’s backstrap.

    16. Mike Mike says:

      Its all water under the bridge if….you don’t practice with the tool of your trade. The reason a majority LEO’s are bad shots is because they don’t practice. The reason they have the few hits they do is because most shots are within 7 yards. Back it up and it would be worse. All this talk about what caliber to use doesn’t mean anything if you can’t hit what your “aiming” at. 9mm .40, .45 they are all good and will lite someone’s ass up…if you know what your doing…and all bad if you don’t. So what does this study really say? Cost of 9mm is cheaper, 40% of FEDS are female so 9mm is easier to handle. This study is to justify the switch for these reason’s only. Angry Misha is Co-RRECT!!!!

    17. Remember; “guns don’t kill people, physics kills people.”

    18. Leviticus says:

      Excellent article! Thank you!

    19. Chieftain says:

      I guess that female thing is why the SAS and the British Commandos/RM have always used either 38’s or 9mm too? Almost every spec ops units in the world us 9mm, and most are using ball ammo, with NATO specs. 124gr FMJ @ 1250 fps.

      In the USA tha equates to a plus “+P” load. In the rest of the world it is the standard for the 9mm Luger.

      For 80 years the knock on the 9 was over penetration. As to the 45acp even the 45’s two biggest cheer leaders, Chuck Taylor & LtCol Cooper admitted that the 45 had problems with penetration. Read their material.

      Also never forget that when Cooper ETAL created IPSC they were terrified of the 9mm dominating. So major & minor were developed to protect the 45 from getting it’s butt kicked. Then the 45 did get kicked by a 9mm variant, the 38super.

      I always found it ludicrous that ‘A’ ring hits counted the same, as it should. But B/C hits counted less? Some how, for religious reasons I guess, when the 45 misses it is a more effective than a miss with the 9mm??? That is nuts.

      Personally I see no need for the 40S&W, either 45 or 9mm for me.

      Simply amazing.


    20. John says:

      So then why did DHS place orders for so much .40 if 9mm is as good?

    21. James K says:

      Good article.Ive always enjoyed shooting all calibers mentioned. I began shooting 10 mm on suggestion of a knowledgeable friend who is way over “they bridge”.At first is was a surprise but wore off quickly by running drills.I have come to trust my skill level with it in a 1911 frame.I also shoot it in glock 20 and 29.The 1911 heavier pistol lends itself to better accuracy.I was told double tap is dead now it’s 2 to mass 1 to head.I think I’ll stick with 10 mm and 300 win mag for now.I load for them and would not want either to make contact ANYWHERE on my body.

    22. J D Jones says:

      ALL ELSE being equal—the larger diameter projectile will do more damage. Obviously the “all else being equal” is the kicker.

    23. Phil says:

      I own all these calibers and love them all. There will always be this debate. Here’s the thing, practice, practice, practice.. Agreed. I work in a large city. Our Department is huge. Issued pistol is a 226 or 229 .40 cal. Here’s the issue I continue to see, although I agree with the “terminal ballistics” of these rounds.. This is with very expensive HP Rounds. Departments buy in bulk, this article and every other debate is “cost savings of the 9mm”. The cost will be significantly more with the critical defense or duty in a 9mm over FMJ 40. I have yet to see HP in any duty pistol here. Not gonna talk about capacity…we can all count. Felt recoil… Well, i think this is gun dependent. Yes there is a difference. Lots of polymer guns boast on the bore axis, this making it a flatter shooting gun. Take a glock vs a M&P, both polymer, both have great bore axis…the grip angle is different. Some say the glock shoots better because the angle. I have both, train with both, shoot both great. Take a common issued sig 226, this gun has a higher bore axis. The glock fanboys all talk about how bad the sig is and it’s high bore axis, sig guys talk about the plastic guns. I shoot my sigs just fine as well. I can feel a difference in them all tho. This is the training part. If you train with all the guns enough, you will learn, overcome, adapt to its downfalls. Train enough and the projectile and “stopping power” gos out the window. It’s about placement of your .22 bullet! Agreed.

      Here’s my point… Most if not the majority of the officers here only “qualify” when required and do not actively train and run drills. There gos the “train train train” and “placement” argument.

      “High performance” ammo? What department buys that? FMJ is the ammo.

      Sad, and I think the standards should be more than just qualifying for one of the largest depts in California. It’s reality.

      So, I can see why the .40 is the choice for here. When shot placement isn’t the best then that “stopping power” comes into play. 45 not enough rounds so go with 40. (FMJ Remember). So for the limited trainer, there will be more missed shots, so when they do hit, the larger FMJ round would be better as well as the most capacity of that bigger round.
      I own all 3 calibers, train with all 3, have the 3 common brands, sig, glock, M&P. I like all.

    24. John Veit says:

      FYI: Here are links to the FBI papers on handgun wounding effectiveness, and the fBI 10mm

    25. JC Blauvelt says:

      As part of my duties when I was a police officer, I attended autopsy’s. One I attended was a victim shot once in the chest with a 22 short rimfire. The bullet went through the shirt, between two ribs, missed the lungs and heart, then into the spinal cord between two vertebra. It was a one shot stop. Do I carry a 22 rimfire based on this one instance? No. I carry a 45 because the larger diameter bullet has a better chance of hitting or nicking one of the CNS spots. A 9mm may expand but a 45 does not shrink. Stay safe brothers.

    26. Bazinga says:

      I find this article very interesting but not surprising. As one who has participated in competitive shooting even at the near entry level, I know for a fact that most LEOs do not shoot well. They rarely even touch their weapon except to shoot their qualifier which is very simplistic. With a little practice, they all should be able to increase their accuracy with minimal effort the force just needs to make it a requirement or else they won’t do it.

    27. Jim22 says:

      The need for training should come from the top – or near it. The average LEO will not train – and continue to train – on his own. Administration should mandate realistic amounts of training. The department should pay the LEO to train as part of his job.

      That is the problem. Administration does not do these things because of the cost. Budgets are a problem. They try to reach a balance between training and expense.

    28. AnointedSword says:

      Looks about right…

    29. MajMike says:

      As far as knockdown power goes we all knew already that Hollywood was BS, however, if you hit a person in a major support bone i.e. the femur or hip or lower spine you probably will knock them down. Doesn’t mean they’re dead yet, so keep shooting until they stop moving or throw away their gun.

      The femur and hip also carry a lot of blood, hitting them will result in rapid loss of a lot of blood. Now, not saying these are the best targets, but you take what you can get (hit) when in a combat situation.

    30. Allen says:

      I just hope everyone is looking at apples and apples. If a 9mm round can be loaded to have the same muzzle energy as 40 s&w does not the laws of physics mean that it would have just as “snappy” of recoil as the 40? Does shooting nothing but +P rounds in a 9mm wear it out just as fast as a 40? Exactly what is the average time difference with double taps in 9mm +P rounds and the 40 calls with each bullet producing the same muzzle energy? Does an attacker feel more energy when shot by a 40 cap that in most cases still have more energy than a 9mm +P round. Will it slow him down on his follow up shot at me offsetting my 1/8 of a second it took me to get the 40 back on line? I have watched bowling pins and steel plates react much better when shot with a 40 call vs a 9mm. I think I will stick with the 40!