In the middle of an emotional town hall event one week after the Parkland shooting, Marco Rubio said something that put him at odds with most Republican lawmakers: Limiting the size of magazines, the spring-loaded devices that feed bullet cartridges into guns, "may save lives" during attacks like the mass shooting at Marjory Stoneman Douglas High School that killed 17 people.

Six weeks after the shooting, the Florida Republican has continued to say that he's open to potentially limiting magazine sizes, though he has yet to support a specific proposal or offer a bill in Congress.

"I have traditionally not supported [a ban] on magazine capacity because I don't think they prevent shootings," Rubio said on Tuesday. "What has allowed me to re-examine it is the reality that in Parkland, at some point in that shooting, whether it was a gun jam or reloading, the shooter had to stop and people got away. And so, the purpose of my opposition has always been that I didn't think it would make a difference and at least in this particular case it might have. Then, if I'm being intellectually honest, I have to look at it again."

Though the Broward Sheriff's Office has not confirmed the type of magazine Nikolas Cruz used in the shootings, a federal law enforcement official told the Times/Herald that all of the ammunition used by Cruz was in 30-round magazines.

But various bills that limit magazine size have traditionally received little support from Republicans. In 2013, the U.S. Senate rejected a ban on magazines that accept more than 10 rounds of ammunition. Rubio voted against that ban, and none of the 51 Republicans currently serving in the Senate voted for it.

Eight states and the District of Columbia have banned what are called "high capacity" magazines, usually devices that hold more than 10 or 15 rounds of ammunition. There are differences between states; some of them permit the possession of magazines above the 10- or 15-round threshold that were purchased before the ban went into effect, while others ban all magazines above the threshold.

"It is clear that any gun in the wrong hands can be used to kill another human being, but when you have weapons that accept either large magazines or just the fact that it has a magazine that can be detached and reloaded, this transforms that killer into a killing machine," said David Chipman, a retired Bureau of Alcohol, Tobacco, Firearms and Explosives special agent who now works as a senior policy advisor for the Giffords Law Center to Prevent Gun Violence, a group that promotes pro-gun-control policies.

Chipman said the 10- or 15-round limit on magazine size is largely based on a desire for law enforcement officers to have superior firepower compared to potential criminals. When he worked as an agent on the ATF's SWAT team, he used a 15-round handgun magazine and a 30-round AR-15 magazine.

"As a law enforcement professional [if] we have a 15-round magazine, it doesn't seem reasonable that someone should have more," Chipman said. "There's some groups that feel like the military and police should have weapons of greater lethality than the public, but then there are pro-gun people who claim they need to have identical weapons. That's where the debate is."

David Johnson, the owner of Johnson Firearms in Wynwood, said that limiting magazine size prevents people from being able to defend themselves.

"Magazine sizes do nothing. If someone takes the time to train, they can pop the mag and reload in the relative same time," Johnson said in an email. "The reason why higher capacity mags are so important for self-defense is statistics show, in a defense situation when your adrenaline is high, the average shooter, including police, will hit their target 6.5% of the time. So with a 10-round magazine, that can equal zero [or] 1 hit."

Chris Koper, a George Mason University professor who researches gun violence, recently studied shootings in Minneapolis, Minnesota. His 2018 report found that incidents where 11 or more shots were fired accounted for 15.7 to 18.6 percent of all shootings in the city, but accounted for 20 to 28 percent of shooting victims, and were more likely to involve multiple victims.

Though Koper cautioned that more research is needed, "restrictions on large capacity ammunition magazines may have greater potential for preventing shootings than has been previously estimated."

Koper also authored a report in 2004 funded by the Justice Department to assess the impact of the federal ban on assault weapons and magazines with more than 10 rounds from 1994-2004. His report concluded that gun crimes involving assault weapons declined during the time period, though there was a growing use of other weapons that used larger magazines grandfathered in before the federal ban.

"The failure to reduce [large capacity magazine] use has likely been due to the immense stock of exempted pre-ban magazines, which has been enhanced by recent imports," the report said, as foreign magazines manufactured before the ban were allowed into the country after the ban took effect.

State Rep. Carlos Guillermo Smith, an Orlando Democrat, unsuccessfully introduced a ban on magazines that hold more than seven rounds during the 2017 and 2018 Florida legislative sessions after the 2016 Pulse shooting. His ban was more restrictive than those in eight states that currently ban certain magazine sizes. His banned magazines with more than seven rounds, though he plans to change it in the future.

"Even I was willing to compromise," Smith said. "I plan to reintroduce this legislation for the third year in a row, but my intent in 2019 is to revise the cap on magazines from 7 to 10 rounds."

Smith said his bill was inspired by the Connecticut legislature's successful attempt to change gun laws after the Sandy Hook school shooting in 2012.

"I can make a solid argument that the effectiveness of a large-capacity ban is more effective than a ban on assault weapons," Smith said.

Smith argued that banning guns like the AR-15 amounts to banning a piece of hardware that can function effectively for decades. For example, the federal government banned the manufacture of machine guns for private use in 1986, but legal machine guns manufactured before 1986, though expensive, can still be purchased.

In contrast, magazines are cheaply constructed compared to guns. A large-capacity magazine is typically made with aluminum or cheap steel and must be replaced every three to four years if used often, Smith said.

"If you look at it from that point of view and that perspective, drying up the supply of large-capacity magazines can be more effective than just banning the firearm itself," Smith said. "Over the long term as long as we keep these bans on place, eventually that supply withers down."

Smith and Chapman also said that banning certain types of magazines would not make it harder for a law-abiding gun user to obtain ammunition for their weapon. Detachable magazines for most firearms have various capacities and manufacturers can easily make new magazines that correspond to new laws, they said.

But limiting the amount of bullets in a magazine will likely always be a non-starter for most gun-rights groups like the National Rifle Association.

That leaves Rubio in a potential no man's land. A proposal to limit magazine size in the U.S. Senate hasn't been cosponsored by any Republican. A proposal in the House of Representatives to limit magazines has 105 cosponsors, and none of them are Republican.

Rubio says he's been talking to stakeholders on both sides of the issue about the policy implications of a limit on magazine size, though he declined to say who he was working with. A spokesperson for the Giffords Law Center said they have reached out to Rubio's office twice but have yet to speak with him about magazine limits.

Rubio acknowledges that magazines that hold more than 10 rounds aren't a tool for hunters. The debate about them centers specifically on how much firepower is needed for self-defense and whether law-abiding firearm owners should have access to less firepower than a potential criminal.

"Frankly, I haven't figured out how to regulate it in a way that could also pass," Rubio said. "Some people just want to ban them. I'm not sure that's the right answer."

Miami Herald staff writer Jay Weaver contributed to this report.