More bullets, more fatalities.

That, in a nutshell, is the conclusion of a new Columbia University study which posits that banning large-capacity magazines (LCMs) could substantially lower the death toll in mass shootings.

“Whether or not to ban large-capacity magazines is at the heart of the national debate over how to reduce gun violence,” said Louis Klarevas, a research professor at Teachers College and the lead author of the study. “Our research suggests that imposing tight restrictions on LCMs offers a practical legislative solution for helping to safeguard Americans from the threats of mass shootings.”

Also called high-capacity magazines, LCMs are detachable ammunition feeding devices that hold more than 10 bullets and allow a shooter to keep firing without having to pause to reload.

Klarevas said their research suggests the odds of a person surviving a mass shooting go up significantly when the shooter's weapon is not equipped with an LCM.

“Think back to the 2011 rampage in Tucson that targeted the crowd as a political meet-and-greet hosted by former Arizona Congresswoman Gabrielle Giffords,” Klarevas said. “The gunman in that attack used a handgun armed with a 33-round magazine to kill six and wound another 13, including Representative Giffords. Imagine how many victims would have been spared if the gunman had fired 23 fewer bullets that day.”

The Columbia study is likely to buttress a drive supported by Connecticut Sens. Chris Murphy and Richard Blumenthal, both Democrats, to pass a Keep America Safe Act that would limit all rifle and handgun magazines to 10 rounds. The gunman, who in 2012 murdered 20 first-graders and six staffers at the Sandy Hook Elementary School in Newtown, Connecticut, had 30 round magazines.

“They are force multipliers for evil,” Blumenthal said when the bill was unveiled. “Guns become doubly and triply deadly because of high-capacity magazines. There is no more simple, straightforward way to save lives than to ban high-capacity magazines.”

Neil Heslin, whose 6-year-old son, Jesse Lewis, was one of the Sandy Hook Massacre victims, supported a large capacity magazine registry as part of the gun control package that Connecticut legislators passed after the 2012 massacre.

"But I'm not a big supporter of banning large capacity magazines," Heslin said. "It's not really a practical solution because so many of those magazines are already out there. The best solution to cut down or eliminate school shootings is armed security. You have to stop the shooter before they get into the building."

Heslin's stance is at odds with gun control groups that grew out of the Newtown tragedy like Sandy Hook Promise, which has actively campaigned to make LCMs illegal.

"Our loved ones were murdered at Sandy Hook Elementary by a shooter who used 30-round ammunition magazines," the group' website says. "When he paused to reload, 11 children were able to escape."

There was no immediate response from the National Rifle Association to the new Columbia University study, but the gun group has long opposed any attempts to ban them.

To reach their conclusions, the Columbia researchers took a closer look at mass killings from 1990 to 2017, which they defined as six or more victims shot to death “not including the perpetrators.”

They chose to start with 1990 because that was the year New Jersey became the first state to ban LCMs. Since then, eight other states and the District of Columbia have also banned them.

That period included the 10-year span starting in 1994 when the possession or sale of LCMs were prohibited under the federal assault weapons ban, which expired in 2004.

Of the 69 “high-fatality mass shootings” during that period, 44 (64 percent) were perpetrated by shooters equipped with LCMs, 16 (23 percent) did not, and in nine cases (13 percent) “we could not determine whether LCMs were used,” the study found.

“LCMs provide a distinct advantage to active shooters intend on murdering numerous people,” the researchers found. “They increase the number of rounds that can be fired at potential victims before having to pause to reload or switch weapons.”

The new study comes as New York Attorney General Letitia James and 18 other attorneys general are throwing their weight behind Vermont, whose 2018 ban on LCMs is now being challenged in court as unconstitutional by a self-described white supremacist named Max Misch.

James argued that the right to bear arms does not mean states are prohibited from enacting “common-sense gun safety measures.”

“Restricting large-capacity magazines means a mass shooter must reload or switch weapons, giving bystanders more opportunities to flee, take shelter, or intervene,” their brief states. “At the same time, there is no proof that large-capacity magazines are necessary – or even commonly used – for self-defense.”

In New Jersey, Gov. Phil Murphy signed a law last year that limited most gun owners to magazines that hold 10 rounds of ammunition instead of 15-round limit that had been in place since 1990.

It was immediately challenged by a NRA-affiliated local gun group. And in December, a split U.S. appeals court upheld the state’s new law.

In California, a federal judge in April blocked California’s ban on LCMs over Second Amendment concerns. But two weeks later, the same judge halted sales of the high-capacity magazines to give state officials a chance to appeal his order.

Surprisingly, it was a gun manufacturer who was one of the earliest champions of banning LCMs.

Back in 1989, when Congress was looking to outlaw high-powered weapons after a series of mass shootings, Sturm, Ruger & Co. co-founder William Ruger Sr. proposed a ban on high-capacity magazines to Congress.

"The best way to address the firepower concern is therefore not to try to outlaw or license many millions of older and perfectly legitimate firearms (which would be a licensing effort of staggering proportions) but to prohibit the possession of high capacity magazines," he wrote.