Banning Large-Capacity Magazines Effective in Curbing Gun Violence, New Study Says

Assault Weapon Large Magazine
A Colt AR-15, flash suppressor, collapsible stock and a high capacity magazine that holds more than 30 rounds, sits on the counter of a gun shop on September 13, 2004 in Denver, Colorado. Thomas Cooper/Getty

Amid a national debate about federal gun control and how to safeguard public spaces, a landmark study is offering new evidence to support targeted public safety measures, specifically, a ban on large-capacity magazines.

The study, led by Louis Klarevas, research professor at Teachers College, Columbia University, is one of the only comprehensive assessments of large-capacity magazine bans in the United States. Klarevas's study, selected for publication in the American Journal of Public Health, looked specifically at high-fatality mass shootings, defined as incidents in which six or more victims died. His research found that death tolls were 62 percent higher on average when large-capacity magazines was used.

"The data supports the idea that when you use large-capacity magazines, you're likely to kill a lot more people," Klarevas said in an interview with Newsweek. "It can be used to escalate the fatality toll of a mass shooting, and that's in fact what the data is showing."

Notably, Klarevas' research did not just find that eliminating large-capacity magazines, defined as an ammunition container with room for at least 10 bullets, was effective, but that laws banning their possession achieved tangible results.

From 1990 to 2017, more than three-quarters of high-fatality mass shootings involving large-capacity magazines occurred in states which lacked a ban on those devices. By comparison, high-fatality mass shootings that did not involve large-capacity magazines were distributed much more evenly: 50 percent took place in non-ban states.

This suggests that laws on the books prohibiting the possession of large-capacity magazines resulted in proportionately fewer shootings involving these devices, which make each individual incident deadlier.

The data directly supports this idea. Eighty-one percent of high-fatality mass shootings in non-ban states involved a large-capacity magazine. In states with a ban, only 55 percent of these incidents involved a large-capacity magazine, according to the study.

The analysis covered a total of 69 shootings over 28 years. Of the shootings studied, in nine incidents it could not be determined whether a large-capacity magazine was involved, introducing a small measure of uncertainty into the results. Nevertheless, even if each of those nine incidents could be assumed to have involved a large-capacity magazine, which they cannot, large-capacity magazine-involved shootings would still prove substantially more lethal than those which did not involve the devices.

In states which did not have a ban, the rate of high-fatality mass shootings per capita was more than double the rate in states which had a ban. This does not mean that these bans decrease the number of incidents, but rather that states which lack a ban see a greater number of mass shootings that rise above the threshold of "high-fatality" as defined in the study.

Assault Weapons Ban
A Glock 9mm pistol is displayed with 2 different capacity bullet clips at a target range on September 11, 2004 in Bossier City, Louisiana. The top clip holds a total of 10 bullets; the bottom clip holds 18 bullets. Mario Villafuerte/Getty

Klarevas explained why removing large-capacity magazines can be effective in reducing lethality:

"If you have to stop to reload, there's this little moment, there's time where people can do one of the three things you learn in active shooter drills: run, hide or fight back. We have evidence that when shooters do reload, people take time to flee or hide."

Lacking a large-capacity magazine, shooters are forced to reload more frequently, giving potential victims an opportunity to escape or rush the assailant.

The study did not measure the number of large-capacity magazines in circulation before or after the bans went into effect. However, Klarevas noted that, while the research did not establish a direct link between bans and de-circulation, "if the laws were effective, we would see fewer mass shootings involving large-capacity magazines, which is what we saw."

The 1994 federal assault weapons ban played a big part in his study. The Clinton-era law prohibited sales of assault weapons and large-capacity magazines. While the federal ban was in effect, through 2004, there were about nine deaths per year from high-fatality mass shootings. After the ban's expiration and through 2017, that yearly death toll skyrocketed to 40.

What's notable about the study is that most of the bans, including both the federal statute and state-level laws, included a provision grandfathering in pre-ban devices. Even with the grandfathered magazines, the results still showed reductions in lethality.

Klarevas noted that his study came with several limitations, including that the results do not measure the effects on gun violence or crime more broadly. Sometimes, distant variables can have unexpected correlations with a study's area of focus. One study led by John Lott, whose methodology has been questioned, purported to provide evidence supporting increased public safety with the enactment of liberal concealed-carry laws. However, as the study noted, if all 50 states were to follow Lott's recommendation, an additional 250,000 property crimes would have occurred.

Another limitation stems from the sparse data on gun violence that is currently available. The reason why Klarevas and his team selected six fatalities as their threshold is because the data on more granular shootings was not reliable. Even still, the team could not be entirely sure it accounted for every high-fatality incident, though an extensive search was performed.

Gabby Giffords And Survivors Of The Tucson Shooting Call For Stricter Gun Control
Former Congresswoman Gabby Giffords and her husband Mark Kelly are joined by survivors of the Tucson shooting as they call for Congress and the Senate to provide stricter gun control in the United States during a news conference on March 6, 2013 in Tucson, Arizona. Giffords and Kelly spoke outside the Safeway grocery store where the shooting happened in 2011 where six people were killed. One study identified the Giffords shooting as the only recent high-casualty incident involving a gunman who was rushed by victims as he was reloading his weapon. Joshua Lott/Getty

Furthermore, as the study cautions, while "69 is a horrific number of incidents, for statistical purposes, it is a relatively small number and limits the power to detect significant associations."

And though the Klarevas study did find strong correlations between bans and public safety, a specific causal mechanism for this result remains elusive. Some research has cast doubt that this mechanism exists at all.

A 2016 study from criminologist Gary Kleck published in the journal Justice Research and Policy examined the different theories behind why large-capacity magazine bans may be effective at reducing lethality.

Kleck found that, from 1994 to 2013, only one mass casualty incident, the shooting in Tucson targeting then-Congresswoman Gabrielle Giffords, involved an assailant being rushed by victims as he was attempting to reload.

He also looked at a separate theory, that mass shooting victims have more time to escape as a smaller-capacity magazine is reloaded. However, in these cases, Kleck found that in the two to four seconds it would take an amateur to reload a magazine, the rate of fire would not be impacted substantially enough to open up a window of opportunity for victims.

While efforts to curb gun violence may be well-intentioned, they often fail when adjacent states have conflicting laws, allowing for easy circumvention by those with criminal intent. Klarevas explained that "large-capacity magazine bans are a strategy for reducing mass shooting violence, not for eliminating it."

Despite the challenges in examining a comprehensive mechanism for gun control legislation and reduction in violence, Klarevas managed to show a strong correlation between laws and outcomes. While future research awaits better data collection and government funding, these initial results on large-capacity magazines do prove somewhat encouraging for public safety advocates.