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By Robert B. Young, MD

The December 18, 2020 issue of the Journal of the American Medical Association included a Quick Uptake news article, “Large-Capacity Magaine Bans Linked With Fewer Mass Shootings, Deaths” (first online December 18). It references a study in the American Journal of Public Health by Louis Klarevas, Andrew Conner and, one of our frequent “guests” here, David Hemenway: “The Effect of Large-Capacity Magazine Bans on High-Fatality Mass Shootings, 1990–2017”.

Essentially, their argument is that “large-capacity magazines” (at least a better phrase than “high-capacity” for those containing more than 10 rounds) are associated with a higher incidence of “high-fatality mass shootings” (those with more than 6 fatalities other than the shooter’s).

Of the 69 HFMSs counted during the study’s 28 years, 44 involved LCMs and 16 didn’t, while in 9 cases magazine capacity couldn’t be determined. Forty-nine occurred in states allowing LCMs compared to 20 where they were banned. More shooters, 81%, used LCMs in states without bans versus 55% in ban states. Likewise, LCM bans were associated with fewer fatalities in each incident (averaging about 7 per shooting in ban states versus about 12 in non-ban states).

That’s a lot of suggestive numbers. But do they really mean that “LCM bans have saved lives”? Let’s look closer.

In 1990, only New Jersey had instituted an LCM ban. From 1994 to 2004, they were outlawed nationally during the federal “assault weapon ban”. From 2004 to 2017, a total of only 8 jurisdictions (7 states and D.C.) had established bans. Which states are not described.

On a very gross level, that’s barely 1/6 of the nation. It very much matters which sixth these are because of how different each state’s mix of urban and rural, economic factors, gun and other cultural aspects. Their covariables of population density, education level, unemployment and incarceration rates, and approximate gun ownership incidence don’t nearly address the distinctions that exist between states.

handgun magazines
Dan Z. for TTAG

This, again, is why only comparing the same geographic area over time is a useful control; comparing one state against another is always comparing apples and oranges. And as always, discovering a difference before and after a change (e.g., LCM bans) is not sufficient analysis—observing a change in trend is necessary.

This is a lot more work—for example, by Mark Hamill’s group that soundly found no correlation between “State Level Firearm Concealed-Carry Legislation and Rates of Homicide and Other Violent Crime”.

Similarly, while the overall increase in incidence of HFMSs is noted, how is this changing in different localities? We can’t tell without know what those places are.

An even more fundamental problem is the definition chosen of a HFMS as one in which 6 fatalities (other than the shooter) occur. There is no clear explanation as to why that number seemed best. They even note that mass murders (“typically defined as ≥ 4 homicides”), not six. In addition, “there has been an average of 2.5 incidents per year”, certainly not enough to draw conclusions about common elements. One has to wonder whether different definitions produce different findings.

For more (and better) information about the relevance of LCMs in shooting, check out Gun Facts. This is a site you should have on top of your gun bookmarks for its great collection of hard data about every aspect of the role and use of firearms in modern life.

Finally, the same elephant is in the room every single time that public health “experts” claim they’ve proven some danger due to the irrationality of allowing American citizens to choose their best defense. There is no consideration of the value of “LCMs” for defense, just as they will never recognize the value of firearms in lawful defense of innocent life.

We know that American civilians probably perform somewhere north of 1 million (per the CDC) to over 2 million (per Kleck) defensive gun uses each year. By any standard, far more lives are saved that way than are actually lost to firearm misuse.

So where is the data on the frequency of gang attacks on individuals, or in multiple assailant home invasions? That’s what we need to compare the questionable danger of LCMs in criminal mass shootings to their value in self-defense against more than a single attacker.

How does this “research”… mislead thee? Let us count the ways:

  • Researcher bias
  • Seeing a firearm accessary as the primary variable (as the prime issue)
  • Likely cherry-picked definitions, and therefore data
  • Setting up straw-man arguments (as if the key to reducing mass shootings is the magazine)
  • Rationalizing that correlation = causation (“the theory   . . . makes sense”)
  • Ignoring data that is far more important that the study variables
  • Insignificant significance in the conclusions drawn (here, on negligible bases)

If this list sounds familiar, it should. Check out our paper, Reading “Gun Violence” Research Critically. You can, too.


DRGO Editor Robert B. Young, MD is a psychiatrist practicing in Pittsford, NY, an associate clinical professor at the University of Rochester School of Medicine, and a Distinguished Life Fellow of the American Psychiatric Association.

This article was originally published at and is reprinted here with permission. 

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    • If you see the name David Hemenway, the answer is YES. He is a biostatistician at Harvard who has been funded by Little Giant for a number of years now. My father in law was a pre-eminent biostatistician, and even as anti-gun as he was, he would be embarrassed by the unprofessional work Hemenway turns out. Hemenway is famous for churning out cherry picked data that when compared to a larger data et completely falls apart. In this particular study, I would guess that the authors did not account for HFMSs that are the result of gang violence. Moreover, simply because a shooter had a 17 round mag doesn’t mean he could not have been just as fatally effective as a shooter with tow ten rounders.

    • This is politically motivated scientism. It is not in any way empirically sound science. First of all we should be very suspicious of all correlational research—crunch the numbers the right way and you can get any outcome you want—which is a favorite tool of people pushing political agendas.

      Every time I read something like this I’m always disgusted by the undisguised bloody-mindedness behind these pretend-science conclusions. Essentially what this guy is saying is that he accepts the premise that spree killings cannot be stopped by armed citizens. Instead, he is suggesting that we should accept mass-shootings as an inevitable reality and—rather than stop them by encouraging an armed citizenry with the ability to fight back—we should take steps to simply reduce the number of rounds spree killers can use as a way of reducing the resulting casualties.

      This idea is not only bloody-minded, it is also supremely stupid and just goes to show the absurd lengths gun-controllers will go to in order to avoid the obvious: the best solution to a bad guy with a gun is a good guy with a gun.

  1. “Essentially, their argument is that “large-capacity magazines” (at least a better phrase than “high-capacity” for those containing more than 10 rounds) are associated with a higher incidence of “high-fatality mass shootings” (those with more than 6 fatalities other than the shooter’s).”

    Just so much Bravo Sierra,one has a difficult time with where to start, fundamentally it doesn’t matter either as a firearm part they are covered/protected by the 2 nd. amendment, Eff JAMA and the grabbers.

  2. Nobody wants data (whatever that means, however derived) that doesn’t prove a political point. Not only, but “data” is first cousin to “need”. As in the “need” to prove that anti-gun sycophants are wrong about the dangers of individual ownership of firearms. And to justify political action to stop gun control laws.

    Just as the label “racist” shuts down conversation, “If it saves only one” tops any argument that there is inherent value to private firearm ownership. Stats and data lead us into the quagmire of relativistic dialectic. As it stands, however, the courts are captive of “need” vs. constitutional principal. Cannot think of a 2A “victory” in the courts that didn’t turn on the interests of government not being persuasive (needs of government v. needs of individuals).*

    *Have not read every 2A ruling in its entirety, so I may have missed one, or two.

  3. I don’t care how many rounds my magazines hold, or what you call them, I’m not surrendering any of them.

    • I’m willing to surrender and comply, if only I hadn’t lost everything during an Alaskan fishing boat accident years ago…life’s tough…

  4. I bet James Campbell has lots and lots of high capacity mags lying around his legs house on a double lot in Dallas, TX.

  5. Just because you have a medical degree doesn’t automatically make you a doctor who morally practices medicine, on a daily basis. Doctors have done great harm historically.

    1. The Nazi Doctors: Medical Killing and the Psychology of Genocide

    2. “During World War II, Nazi doctors conducted as many as 30 different types of experiments on concentration-camp inmate”

    3.Nazi Medicine and the Nuremberg Trials: From Medical War Crimes to Informed Consent

    4. Eugenics in Progressive California lead by “some really great” doctors. No. They aren’t really that great.

      • “The JAMA article was not authored by a medical doctor.
        See my comment below.”

        Maybe the Brits have it right: Physician v. Doctor.

        And Chemist v. Pharmacist

    • Well I’ll save you the work. He has a Ph.D. in International Relations.
      A political (pseudo) “science” degree.

    • You forgot Japan’s Unit 731 which made the worst of the Nazi atrocities look like humanitarians.

  6. The full thing is here:

    The lead Phd on the report acknowledges a conflict of interest, he’s been paid for these opinions.
    L. Klarevas has, in the past 2 years, served as an expert to the states of Colorado and California in civil litigation that involved the constitutionality of state restrictions on large-capacity magazines. The authors have no additional conflicts of interest to report.

    • Kind of shoots down the whole article I bet the author quotes his own article when he testifies as an “expert” witness. On the next page of that issue of JAMA there’s probably an article on the health benefits of tobacco written by a Phillip Morris sponsored expert on tobacco health benefits. I guess the JAMA is published by правда. I never believe anything published in JAMA or NEJM (New England Journal of Medicine)

    • Klarevas holds a B.A. in Political Science from the University of Pennsylvania and a Ph.D. in International Relations from the School of International Service at American University.
      I don’t think either of those degrees make him an expert in medicine, trauma or firearms.
      Hey JAMA! How about publishing some medical articles and leaving the political demagoguery to the New York Times?

      • Doesn’t AOC have a degree in international relations from Boston Univ? Maybe JAMA should ask her to write an article. (Or, did the Babylon Bee already do that?)

    • Might as well get the 100 dual drum. Sure, it’s ridiculously heavy and might jam but if it annoys just one anti-gunner, it’s worth it.

    • I know from experience (back in the 1990s) that changing magazines in a AR-15 takes less time than for me to describe the actions. We had some courses of fire at the range that had mandatory reloads.

  7. Dr. Gary Kleck also did research on regular magazines……what they lie and call large capacity magazines…..and found no correlation…..

    In sum, in nearly all LCM-involved mass shootings, the time it takes to reload a detachable magazine is no greater than the average time between shots that the shooter takes anyway when not reloading. 

    Consequently, there is no affirmative evidence that reloading detachable magazines slows mass shooters’ rates of fire, and thus no affirmative evidence that the number of victims who could escape the killers due to additional pauses in the shooting is increased by the shooter’s need to change magazines.

    • “…no affirmative evidence that the number of victims who could escape the killers due to additional pauses in the shooting is increased by the shooter’s need to change magazines.”

      All well and good, but overlooks the actual fact at play: projection.

      Anti-gun people consider themselves totally reasonable. Since they are reasonable, and do not own guns, no reasonable person would own a gun. Since they are reasonable and do not want guns to be available legally, they cannot imagine any reasonable person would be able to use a gun properly. As such, being reasonable and unfamiliar with firearms, anti-gun people know they would fumble reloads, as would any reasonable person. However, anti-gunners then project onto the mass murderer the anti-gunner’s own inability to properly operate a gun, leading to the conclusion it would take the anti-gunner so long to complete a re-load, that plenty of time would pass to allow someone (someone who is still present during a shooting) to take down the shooter who is fumbling the reload. The more frequent the reload, more opportunities to fumble the reload; more opportunities to tackle the shooter.

      No, anti-gunners do not project this reload failure onto criminals and gangers, who are likely to be proficient at shooting. Why? Because the mass shootings anti-gunners fear are not committed, in nice places, by criminals and gangers.

      • “All well and good, but overlooks the actual fact at play: projection.”

        You’re *close*, but no cigar.

        What this actually is, is a piece to be fit in a puzzle in the future. The future of the Supreme Court. JAMA is considered by the Leftists to be a credible source of research and medical knowledge as it applies to the greater population.

        We will see this in the future when the Leftists dismantle the Constitutionality of gun ownership by the citizens. This will pop up in that decision as evidence that gun ownership is just too dangerous to risk for us little people.

        This is a taste of the long game that the Leftists are playing to enslave us…

        • “This is a taste of the long game that the Leftists are playing to enslave us…”

          I agree. The intent of the comment was to highlight how anti-gunners arrive at their rationale, and why it is persuasive. Some years ago, I pointed out this specious reasoning to my brother-in-law. Even found videos you YouTube demonstrating the near impossibility of taking down a shooter engaged in a reload (the videos did not include “New York” reloads). BIL claimed the videos, even the ones where people who acknowledged they had no experience with guns were doing the reloads, were just a setup. So I asked BIL how anyone could identify a shooter who is most likely to botch the reload, and allow intervention. BIL said that would be case-by-case. I then asked if he, involved as a potential victim, would attack during a reload. BIL allowed as how he would never think to attack during a reload, because it was too dangerous. Irony not appreciated.

  8. The real variable…that isn’t included… long before someone with a gun stopped the shooter……that is the only variable that counts……

    Dayton shooting with magazine…3 killed. Police on hand stopped him almost immediately.

    Russian Polytechnic school shooting, 5 shot, tube fed, pump action shotgun…20 killed with the local police station 300 meters away.

  9. Golly didn’t the Cruz cretin use mere 10rounders? The Navy yard shotgun lunatic less. The San Bernardino “couple” used “illegal” 30 rounders(😩). My FB friend’s in Australia tell me arson is a popular murder method. And blades are the thing merry old England…intent is everything.If you wanna kill you will. I will NOT comply😃

  10. All those words to say nothing more than er aah we don’t know. I’m just waiting for someone to cut and paste the whole article

  11. 1) It seems curious that we keep hearing about how many hundreds of mass shootings there are a year and yet the study only took into account 69 over about 30 years. You have to wonder how many selective biases they built into that.

    2) These number absolutely dwarfed by the homicide rates in places like Chicago and Baltimore (the latter with every gun control wet dream you can imagine)

    3) This argument can, and will be used for ANY armaments that can be used in self-defense. The slippery slope fallacy is not a fallacy with these people.

    This is the kind of propaganda that was the motive to restrict public funding for this nonsense. Let Bloomy spend his billions of dollars on it.

    • “It seems curious that we keep hearing about how many hundreds of mass shootings there are a year and yet the study only took into account 69 over about 30 years.”

      They are cherry-picking the data to match their political agenda…

  12. I own magazines for my various guns in capacities of 4, 5, 6, 7, 8, 10, 15, 17, 20, 25, 30 and 40 rounds. Has to be over a hundred magazines and speed loaders among all those “Assault ammunition feeding devices”. Not a single one of them has ever killed a human animal. Not once, not ever.

    Come to think of it, none of them has ever so much as attempted to kill a human animal. Not once, not ever.

    Damn it all. suddenly I feel like such a failure in the greater JAMA defined view of the world.

    • Living in California, all of mine are ten or less. But they do not seem to have any feelings of inadequacy that tempts to jump out of their holsters and start blasting away.

  13. If we treated doctors the same way we do guns, then we’d have no choice but to ban healthcare due to over 250,000 annual medical deaths (John’s Hopkins study). Without placing gun use in context against all of the good outcomes (including sporting use) it is easier to demonize weapons. Doctors kill more people than guns- should we outlaw them?

    • “Doctors kill more people than guns- should we outlaw them?”

      You’re missing the gun-grabber point: people “need” doctors; no one “needs” a gun.

        • “Still, doctors kill more folks annually than do guns. Period……………….”

          True; meaningless data point for gun grabbers.

          And the undecided, persuadable unicorns.

  14. The whole study is bunkum. What does “large capacity” mean? Federal AWB was >10 rounds. Same with California. NY wanted 7. Virginia wants 12. Colorado has 15. Is any number effective? Can we just have a national ban on large capacity magazines that hold more than a billion rounds and call it quits? 2A absolutists may oppose that, but maybe we can trade it for CCW reciprocity, NFA repeal, or at least removal of suppressors from NFA. California has had a ban for decades and still has mass shooting events.

  15. Well duh, if a shootem upper arrives with more bullets he’s naturally going to do more shootzjng. The answer lies not in the amount the shootzer had , but why the shootzer was shootzings them up in the first place. I think it’s all the radio waves the human brain is now inundated with. Back before radio ,TV, and cell phones a human just didn’t hear about shootem ups as much

  16. Hey JAMA – doing something that is in your wheelhouse. Get to work on the chicom flu NOW. Not in 2 weeks NOW

  17. Well, they could talk about health services, diagnosis, delivery, or effectiveness, but tben they might have to do somdthing themselves.

    “Policy guys” giving themselves a field promotion. Rather than work on their work, they’re telling other people what to do (about telling other do.)

  18. Well, if I had the modern medical profession’s success rate at improving things, I’d want to distract people too.

    How’s containing that corona virus working out? Drug resistant infections n STDs? Obesity n related devenerative conditions? Orthopedic support for aging populations? Statins are a good thing, bad, sometimes, or what’s the protocol today?

    “Medical” progress comes from fundamental science, n dev of new technologies. Docs don’t do that. They’re technicians. So JAMA with newest prescription of “Do this.” is about their speed, but don’t expect them to think.

  19. JAMA has been putting out these flawed gun “studies” for decades. Nobody pays attention to JAMA.

  20. The whole “large capacity” (whatever that means) magazine debate seems kind of pointless as there are many, many millions in circulation and the history of banning them indicates only a small fraction will ever be turned in. The old idiom about closing the barn door after the horse is out comes to mind.

  21. Seems flawed immediately to me because of the fact that a 30 round mag is STANDARD capacity, thus there would be more of them in the sample because it’s STANDARD on the guns they want so desperately to ban, at least in the free states (which is the majority).

    It’s like trying to corelate some kind of connection to vehicle wrecks with fatalities and automatic transmissions.

  22. Just stay in your lane and focus on your patient. Maybe then you would kill fewer of them. If you would do that, you would save way more lives than any gun control laws ever could.

  23. JAMA and the author really need to be concerned with the number of medical malpractice deaths in America each year. It is FOUR times the number of weapon-involved crime deaths.

  24. Most sociological studies are bunk simply because the amount of variables NOT accounted for is always substantially larger than the variables that are accounted. Also, there is the presumption of a control group, but that is not true. We don’t know the murder rate of Missouri from 2000-2014 with gun control laws, and the rate from 2000-2014 without gun control laws. You can’t compare Missouri to New Jersey and pretend you have a control group. From a scientific standpoint all of these studies are just noise but people make good livings pretending they matter, so….. Since journalists are literally the dumbest people on the planet*, don’t expect any rational analysis of these kind of things.
    *Ben Rhodes, national security adviser to Pres. Obama said it, not me

  25. Kleck published a paper in 2016 showing just the opposite–large cap mags are not correlated with the number of deaths in mass shootings. Who do you believe?

      • Sorry for the lack of computer savvy, but this is the paper:

        Large-capacity magazines and the casualty counts in mass shootings: the plausibility of linkages.
        Gary Kleck, Justice Research and Policy, 2016, volume 17(1), pp. 28-47.

  26. First of all, the number of mass shootings themselves is statistically insignificant relative to total firearms homicides. Further, mass shootings performed with a rifle with a standard capacity magazine (30 rounds) is an even smaller subset.

    There isn’t enough data to draw such conclusions.

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