(NEW YORK) — When an 18-year-old shooter arrived last week at Robb Elementary School, in Uvalde, Texas — where he ultimately killed 21 people, including 19 children and two teachers — he carried 1,657 rounds of ammunition, authorities said.

The large number of rounds should not come as a surprise, experts told ABC News. The tragedy drew renewed scrutiny to a collection of state and national laws that regulate ammunition less tightly than firearms, despite the vital role played by ammunition in mass shootings, experts said.

A shooter at a Las Vegas music festival, in 2017, who killed 59, had at least 1,600 rounds. A shooter at an elementary school in Sandy Hook, Connecticut, in 2012, who killed 27, had more than 1,700 rounds of ammunition at his home. And a shooter at a movie theater in Aurora, Colorado, also in 2012, who killed 12, had bought more than 6,000 rounds, officials said.

Current regulations often allow for the purchase of massive amounts of ammunition and high-capacity magazines without a background check or even a face-to-face interaction, experts added.

While gun control proponents say ammunition deserves stronger restrictions that would limit the frequency and severity of mass shootings, gun rights advocates argue that ammunition restrictions violate Second Amendment protections and unnecessarily duplicate the regulations in place for guns, experts said.

“There are fewer restrictions on ammunition sales than there are on firearm sales both at the federal level and in the vast majority of states,” Jacob Charles, executive director of the Center for Firearms Law at Duke University School of Law, told ABC News.

“Someone intent on a mass casualty event is going to have enough ammunition to be able to keep shooting until they’re stopped,” he said.

Federal law prohibits the sale of ammunition in a narrow set of circumstances, experts said.

People cannot purchase or possess ammunition if they’ve been convicted of a felony or misdemeanor domestic violence, committed to a mental institution, or if they belong to a handful of other categories deemed at-risk, experts said.

Also, under federal law individuals must be at least 18 to buy rifle or shotgun ammunition, and at least 21 to buy ammunition for any other guns. On top of that, in 1986, the U.S. enacted a law that bans armor-piercing bullets, which became notorious for the threat they posed to police officers.

Absent from national regulations are measures that require background checks for the buyers of ammunition or licenses for the sellers, which undermines enforcement of the few federal laws that are on the books, Tom Donohue, a law professor at Stanford University who specializes in gun legislation, told ABC News.

“Any restrictions on ammunition at the federal level are virtually feckless because you don’t have to go through a background check to purchase ammunition,” he said.

Federal law also lacks a measure that addresses high-capacity magazines, which enable shooters to fire a large number of bullets without stopping to reload. Such a law did exist once at the national level: The assault rifle ban enacted by Congress in 1994, which lapsed 10 years later, included a ban on high-capacity magazines.

A study published in 2019 by three researchers, including David Hemenway, director of the Harvard Injury Control Research Center, examined mass shootings over a nearly three-decade period and found that attacks involving high-capacity magazines had a 62% higher average death rate than those without them. The study also showed that high-fatality mass shootings occurred more than twice as often in states without bans on high-capacity magazines than in states with them.

In all, nine states have enacted bans on high-capacity magazines, including predominantly Democrat-controlled states like New York and Connecticut, according to the Giffords Law Center to Prevent Gun Violence.

The landscape of high-capacity magazine bans reflects a general trend of state-level measures that strengthen ammunition laws in a small group of mostly blue states, while the remainder of states go no further than federal law, Charles said.

For instance, New York and California have instituted mandatory background checks for ammunition purchases at the time a sale takes place, Charles added.

Gun rights advocates staunchly oppose ammunition regulation, experts said. Gun proponents argue that there’s no need for additional regulation of ammunition once an individual has been deemed fit to own a gun.

“In theory, if I have given you a license and found you to be a law-abiding citizen, there’s no reason for me to care what kind of gun you buy or how much ammunition you buy or what else you do, as long as it’s legal,” Alexandra Filindra, a political science professor at the University of Illinois, Chicago who studies gun laws, told ABC News.

Similarly, gun rights advocates have argued that regulation of ammunition infringes on their Second Amendment protections in the same manner that gun regulations do, since ammunition is a necessary part for operating a gun, Filindra said.

“The theory goes that essentially you are implicitly regulating gun ownership by taking away people’s ammo,” she said.

A network of gun rights groups, most notably the National Rifle Association, has fought ammunition regulation by framing it as an attack on gun ownership, the experts said.

“The same group standing in the way of gun safety reform is standing in the way of ammunition reform,” said Ari Freilich, the state policy director at Giffords Law Center.

Some ammunition-related bills have been introduced in Congress. The Age 21 Act, put forward by Senator Dianne Feinstein, D-Calif., would raise the minimum age for buying assault rifles and high-capacity magazines from 18 to 21. Meanwhile, a bill in the House would require a license for all ammunition sellers and mandate that all ammunition sales take place in person.

Experts said that meaningful reform of ammunition laws is unlikely in the short term, but some said that incidents like the mass shooting in Uvalde make action more likely in the long term.

“A lot of people have woken up to how senselessly, dangerously reckless our lack of protections currently are,” Freilich said.

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(WASHINGTON) — Adm. Linda Fagan became the first woman to lead a branch of the U.S. military when she was sworn in as commandant of the U.S. Coast Guard at a sunny ceremony in Washington on Wednesday.

President Joe Biden, who nominated Fagan to the post in April, spoke at the change of command event at U.S. Coast Guard Headquarters, calling it “a new milestone in our history” and “a big deal.”

“There’s no one more qualified to lead the proud men and women of the Coast Guard, and she will also be the first woman to serve as Commandant of the Coast Guard, the first woman to lead any branch of the United States Armed Forces — and it’s about time,” Biden said at the ceremony, where Fagan relieved Adm. Karl Schultz, who is retiring.

Biden added, “Secretary of Defense, when he sent me the name, I said, ‘What in the hell took you so long?'”

Fagan is coming off serving as the Coast Guard’s vice commandant — the first female four-star admiral to serve as a branch’s second-in-command — and previously served as the commander of the Coast Guard Pacific Area from June 2018 to June 2021.

Now, Fagan will soon be the first woman to take a seat at the table of the U.S. Joint Chiefs — representing all branches of the military — and she comes equipped with nearly 40 years in the service, on par with the officers she will be joining.

“I’m immensely grateful to the many players that paved the way,” Fagan said following Biden. “Pioneers like Admiral Siler, Dorothy Stratten, Ida Lewis, Dorothy McShane, Elizabeth Friedman. I’m proud to be a part of this long history of service, dedication, and groundbreaking, and I’m committed to carrying these principles forward.”

Biden noted that Fagan had been a pioneer earlier in her career, too, serving as one of few women — or the only woman — in various stations throughout her time in the service, and calling Wednesday’s ceremony “a historic first, in that effort.”

“I want to thank you Admiral Fagan for taking the helm during this critical moment,” he added. “And for all that you’ve done throughout your career, it opened the doors of opportunities just a little bit wider to allowing those following behind you, a way through.”

Biden also emphasized that the U.S. needs to ensure that more women are in leadership positions at Fagan’s level.

“We need to ensure women have an opportunity to succeed and thrive throughout their professional careers and that means providing support and resources so women can compete fairly and fully for promotions and make sure women are not penalized in their career for having children,” Biden added. “It also means creating an environment where every member of the Armed Forces feels safe in the ranks, including from sexual assault and harassment, and where their contributions are respected.”

In 1985, Fagan was in just the sixth graduating class from the Coast Guard Academy that included women. She has since risen the ranks to serve on all seven continents — “from the snows of Ross Island, Antarctica to the heart of Africa, from Tokyo to Geneva,” according to the Coast Guard — and aboard the USCGC POLAR STAR, a 399ft heavy polar icebreaker. She is also the longest service in the marine safety field, which earned her the Coast Guard’s first-ever Gold Ancient Trident distinction.

During Fagan’s confirmation hearing before the Senate Commerce Committee, which has oversight of the Coast Guard, lawmakers on the panel including Chair Sen. Maria Cantwell, D-Wash., praised her qualifications and place as a trailblazer.

“We’re sending a strong message to women cadets and to people training at Cape May. And we are sending a strong message to young girls who dream of someday serving in the Coast Guard,” she said. “We are saying now that the leader of this organization that your service matters, your contribution to the Coast Guard and to the country matters. And yes, you too can be commandant someday.”

Notably, Fagan’s daughter, Aileen, is also a Coast Guard lieutenant and was present at Wednesday’s ceremony.

“Thank you, Mr. President, for calling her out,” Fagan said in her remarks, after Biden had thanked her family for being there. “She’s my personal aide. I lean on her pretty heavily.”

Born in Columbus, Ohio, Fagan also earned degrees from the University of Washington and the Industrial College of the Armed Forces.

Other prior assignments include Deputy Commandant for Operations, Policy, and Capability, Commander of the First Coast Guard District, and a joint assignment as Deputy Director of Operations for Headquarters and United States Northern Command.

The Senate approved Fagan’s nomination, along with five other senior Coast Guard officers, by unanimous consent last month.

ABC News’ Luis Martinez contributed to this report.

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