WASHINGTON — It's become almost a mythic tale passed around after mass shootings, raised by everyone from President Barack Obama to student survivors of the Parkland attack last month: Australia faced a similar problem with guns — and they solved it.

After a gunman with an AR-15 rifle and high-capacity magazines opened fire at a tourist site in Port Arthur and killed 35 people in 1996, a conservative government led Australian states in passing sweeping new restrictions on firearms. Authorities collected and destroyed over 640,000 weapons, as many as one-third of all guns in the country — whether their owners wanted to part with them or not.

In the years afterward, gun violence and gun suicides plummeted, and no similar attacks occurred. The prime minister at the time who oversaw the policy, John Howard, has urged the United States to follow his approach. A paper by Australian researchers released on Monday, including an academic who was a prominent advocate for the 1996 law, suggests the policy may have prevented 16 mass shootings based on previous rates of attacks.

"(They) took ideas, put legislation together, and they stopped it," Sam Zeif, a student at Marjory Stoneman Douglas High School in Parkland, Florida, who survived the Feb. 14 shooting, said in a televised White House meeting. "Can anyone here guess how many shootings there have been in schools in Australia? Zero."

Australia has become a source of inspiration for politicians, activists and voters in America seeking stricter gun laws. But it hasn't become a policy model.

Almost none of the major gun violence prevention groups are advocating anything similar to Australia's mandatory gun buyback program. Neither are elected officials in Washington.

"I haven't seen any serious proposal like that in the United States," Adam Winkler, a law professor at UCLA and author of "Gunfight: The Battle Over the Right to Bear Arms in America," said.

With some exceptions at the state and local level, nearly all policy proposals to restrict certain types of guns include a grandfather clause that allows people to keep existing firearms and accessories. Advocacy groups are wary of feeding accusations that they plan to take guns away rather than place restrictions on sales that would keep them from bad actors. Calls for a federal effort to ban and then forcibly remove private guns have mostly been limited to individuals.

"I think it's pretty clear from the program we do support that it's about keeping guns out of dangerous hands and not about confiscating guns," Kris Brown, co-president of the Brady Campaign, which advocates against gun violence, told NBC News.

While Australia's methods are considered a nonstarter in the United States, advocates for stricter gun laws still have to tackle the same problem: If the goal is to remove certain guns from circulation, what do you do if there are already millions available?

After a mass shooting, Australia decided: It wanted most of its guns gone. So it bought them back from owners, by the thousands. David Gray / Reuters file

'A tough sell'

Gun safety activists and researchers examining gun violence see multiple reasons, some political and some practical, why an Australia-like gun ban is unlikely to take off.

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For one, the United States has a uniquely strong gun culture — gun ownership is written into the nation's founding document. Any talk of taking guns sparks an immediate backlash from gun rights groups, which have long rallied supporters by warning more modest restrictions are a first step toward a broader crackdown. Prominent activists and politicians who mention Australia often gloss over the mandatory buyback element and pro-gun activists are eager to highlight exceptions.

"They want mandatory buybacks, that's what they push," NRA spokeswoman Dana Loesch said in a recent NRA-TV appearance.

Loesch cited media appearances by Mark Glaze, a co-founder of Guns Down, in which he mentioned Australia's forced gun sales as a possible model. Guns Down favors reducing firearm ownership nationally and employs harsher anti-gun rhetoric than established advocacy organizations, but even Glaze says that Australia's approach is far down his priority list.

"Compulsory buybacks would be a tough sell here, certainly federally," Glaze said in an interview.

Just as Australia's laws are a rallying cry for gun control supporters on social media, they're also a flashing alarm for gun rights activists.

"[The] ongoing destruction of personal freedom in Australia stands as a stark and constant reminder of just how far gun control extremists are willing to go in their quest to disarm law-abiding citizens," Chris Cox, executive director of the NRA's Institute for Legislative Action, wrote in November.

Cox pointed to research suggesting that, while firearm-related deaths in Australia had dropped since 1996, the impact of the law was less clear, and noted that mass shootings are so rare that it's hard to determine their cause.

While Obama never proposed confiscating guns himself, his frequent praise for Australia's policy in his second term prompted an outcry from the NRA, who argued it exposed his true position. After Hillary Clinton told a New Hampshire voter interested in Australia's approach that it was "worth considering," she was assailed by Second Amendment activists and her campaign quickly clarified she "does not support national mandatory gun buyback programs, including those modeled after Australia's program."

But even if an Australia-style law passed tomorrow, there would still be practical concerns, in large part because America has so many guns.

As of 2009, there were over 310 million privately owned firearms, according to a 2012 Congressional Research Service report. There's no definitive figure on the number of "assault weapons" like the AR-15, a disputed term whose definition could change depending on legislation, but the high-end estimate by the NRA is 15 million.

David Chipman, senior policy advisor to the Giffords Law Center to Prevent Gun Violence and a former ATF agent, said the sheer number would not only raise the costs of a buyback program (AR-15-style rifles can run over $1,000), but make enforcing it difficult. As it stands, Chipman described the ATF as badly underfunded and undermanned, in part due to opposition from gun rights activists. There were just over 5,000 full-time staff in the 2016 fiscal year.

"In a buyback plan, I still don't know what we would do if only 1,000 people showed up and you knew there were still millions of guns out there," Chipman said.

That type of widespread noncompliance appears to be a likely scenario based on the experience of states who expanded gun laws in the last few years. California banned ownership of high-capacity magazines last year, but there's little sign that many owners turned them in to police. States like Connecticut and New York that passed laws requiring residents to register assault weapons found the number of people who came forward lagged far below estimated ownership.

Alternative approaches

Twenty years ago, Australia scrapped gun ownership. Literally. David Gray / Reuters file

Legislators and advocates have proposed a variety of ways to reduce gun violence while avoiding Australia's direct confiscation of broad classes of firearms.

One option, favored by the Giffords Law Center, is to regulate ownership of weapons covered in a new Assault Weapons Ban differently than other firearms, and expand the ATF's funding to manage the new rules. They propose treating them like machine guns, which can no longer be manufactured but whose existing stock were grandfathered in when they were banned. Under the National Firearms Act, owners have to register these restricted weapons with the ATF, undergo a background check and pay a $200 tax. The machine guns in circulation today are rarely associated with crimes.

"It allows Americans who want these guns and think they're important to stay straight with the law and keep them registered," Chipman said. "If they choose not to, they'll be duly warned that they're not just breaking some local ordinance but a strictly enforced federal law with severe consequences."

So far, proposed legislation wouldn't go quite as far. New versions of the Assault Weapons Ban in the House, backed by Reps. David Cicilline, D-R.I. and Ted Deutch, D-Fla., and in the Senate, authored by Sen. Dianne Feinstein, D-Calif., would require owners of grandfathered weapons to store them securely and employ a background check if they sold or transferred them.

With the supply of guns unlikely to be significantly diminished anytime soon, however, lawmakers in both parties have also looked more at demand. The White House and a variety of lawmakers have looked at proposals to implement gun restraining orders, which would allow police, family and friends of gun owners to seek a court order temporarily confiscating their weapons if they feared they had become a threat.

More likely to pass is the Fix NICS Act, a bipartisan measure backed by Senate Majority Whip John Cornyn, R-Texas, that would encourage states and federal institutions to improve background checks. Manchin-Toomey, a bipartisan bill that would require background checks for more private and online sales, is stalled, although its sponsors have said they're looking for support.

At the state level, Florida legislators recently voted against an assault weapons ban in response to the Parkland shooting. But Gov. Rick Scott, a Republican, signed a new law that raises the minimum age to buy a firearm to 21, adds a three-day waiting period, bans both the sale and possession of "bump stock" accessories that increase firing rates, imposes new restrictions on sales to mental health patients, and frees up schools to arm some staff members.

One option might just be patience. Advocates said that restrictions on high-capacity magazines or assault weapons could eventually make them harder to obtain, but only over a long timespan.

Jon Vernick, co-director of the Johns Hopkins Center for Gun Policy and Research, likened the problem of existing firearms to an overflowing sink that had flooded every room.

"Even if it means it's going to take awhile for your house to dry out, that doesn't mean turning off the tap isn't the right thing to do," he said.