Gun enthusiasts look over Smith & Wesson pistols at the NRA Annual Meetings & Exhibits on May 21, 2016 in Louisville, Kentucky. About 80,000 visitors are expected to attend the three-day event. (Photo by Scott Olson/Getty Images)

An unknown number of guns are being built with the mechanisms, causing problems for the police and ATF officials. Photo: An ATF agent holds a generic unfinished receiver, back, and one that has been manufactured, front, at an ATF field office in Washington, on May 06, 2014. The ATF is trying to crack down on the trade in the makeshift guns by targeting shops and individuals who offer to turn the unfinished receivers into functional pieces for firearms. (Photo by Bill O'Leary/The Washington Post)

Stuart Craig of Washington tries out a Sig Sauer 1911 model Scorpion pistol at the Sig Sauer booth at the National Shooting Sports Foundation's 34th annual Shooting, Hunting, Outdoor Trade (SHOT) Show at the Sands Expo and Convention Center January 17, 2012 in Las Vegas, Nevada. The SHOT Show is the largest annual gathering of shooting professionals with more than 1,600 exhibitors and 30,000 attendees expected. (Photo by Ethan Miller/Getty Images)

The best man in a wedding party, who all declined to be identified, stands near the bride and groom as he holds an AR-10 rifle he was handed while the party was having their pre-wedding portraits taken on the steps of the capitol before a rally nearby by gun-rights advocates to protest a new expanded gun background check law in Washington state Saturday, December 13, 2014, in Olympia, Wash. The wedding party was not part of the protest, but posed for pictures with it after being handed it by gun activist Brandon Lyons, who said “we've all just broken the law”, by handing the gun over. Saturday's protest was called the “I Will Not Comply” rally, and those attending said they will openly exchange firearms in opposition to the state's new voter-approved universal background check law, Initiative 594. The law, which took effect on December 4, requires background checks on all sales and transfers, including private transactions and many loans and gifts. (Photo by Elaine Thompson/AP Photo)

Lady officers of the Philippine National Police force show the taped muzzle of their guns at a police camp in Taguig City, south of Manila, Philippines, 22 December 2014. Law enforcement units all over the country held a ceremonial taping of firearms as a counter measure against cases of indiscriminate firing and illegal discharge of service weapons during the upcoming Christmas and New Year celebrations. (Photo by Francis R. Malasig/EPA)

A woman with a snake on her body, taken in Rio de Janeiro, Brazil, April 2017. A holistic therapist uses snakes to massage her clients – claiming it cures depression and even helps victims of abuse. Instead of traditional massaging techniques, Sarah Zaad uses up to six pythons and boa constrictors on brave customers who want to relax or be treated for mental disorders. The flamboyant therapist from Rio de Janeiro, Brazil believes her snakes have a magic touch, which can benefit people by massaging their bodies. (Photo by Kadeh Ferreira/Barcroft Images)

A woman is having a massage at the Lukacs Bath in Budapest, Hungary June 28, 2016. Hungary's capital owes its popularity as a tourist destination partly to its numerous hot springs and bathing culture which have drawn visitors to the area since Roman times. Bath houses range from large, ornate 19th-century buildings like the Gellert and the Szechenyi to tiny Ottoman Turkish-era hamams, some of them more than 500 years old. (Photo by Bernadett Szabo/Reuters)

Thailand's badminton player Ratchanok Intanon, who hopes to win gold at the Rio Olympics, receives a massage during a morning training session at a gym in Bangkok, Thailand, June 22, 2016. As the humble daughter of factory workers at a Bangkok sweet-maker, badminton was a ticket out of poverty for Ratchanok Intanon, who hopes winning gold at the Rio Olympics might inspire more Thai girls to chase their dreams. (Photo by Athit Perawongmetha/Reuters)