Cheap switches deliver machine-gun firepower across US

A piece of metal the size of a small coin that can convert a semi-automatic weapon to a fully automatic machine gun capable of firing up to 1,200 bullets a minute is increasingly being used in the United States, according to the agency responsible for firearms.

The "auto sear, Glock switch or chip" is being bought online or made with a 3D printer, said the Bureau of Alcohol, Tobacco, Firearms and Explosives, or ATF. They cost under $100.

The bureau said that over the past year and a half it had seized more than 100 modified guns in Memphis, Tennessee, and western parts of the state and Alabama. In 2021, the ATF seized 1,500 weapons nationwide that used Glock chips, a huge jump from the 300 seizures in 2020.

Guns with the switches also have shown up in California and in Washington, where the Metropolitan Police said the number of modified guns with auto sears it recovered in the first half of 2020 was 10, but that figure doubled to 20 in the first half of 2021.

In 1986, Congress passed the Firearms Owners Protection Act, which prohibits the import or manufacture of any new automatic weapons.

The switch devices are classified as machine guns by the ATF. Anyone found with one can face 10 years or more in prison. The switches are like bump stocks used on rifles to increase firing. Bump stocks became illegal in 2019.

Many of the auto sears are sold on the black market or imported.

Mickey French, the special agent in charge of the ATF's Nashville, Tennessee, division, told an NBC affiliate in May that auto sears are "hidden in how they are marketed", and that presents a "challenge to law enforcement".

The auto sear prevents the trigger on a gun from resetting so it can be pressed once to empty a magazine.

While a Glock gun fires 15 rounds in 8.32 seconds, a Glock switch or auto sear turns it into an automatic that can fire 30 rounds in just 2.3 seconds, double the number of bullets in a quarter of the time.

Concern over the use of Glock switches comes amid heightened fears about guns following mass shootings at a school in Uvalde, Texas, and at a supermarket in Buffalo, New York.

In April, a gunman armed with a modified Glock opened fire in Sacramento, California, killing six people and wounding 12 others.

In May 2020, Steven Carrillo, 32, a member of the anti-government group the Boogaloo Bois, shot at two security officers outside a federal building and courthouse in Oakland, California. He killed one and wounded the other using a homemade AR-15, which had been turned into a machine gun with an auto sear. He was sentenced to 41 years in prison.

On April 11, more than 40 members of Congress signed a letter urging the ATF to be more aggressive against the rise in auto sears and Glock switches.

Early on Monday, a shooting at a gathering in Harlem left a man dead and eight others wounded, New York City police said.

More than 20,000 people have died due to gun violence in the US this year, data from the Gun Violence Archive shows.

Agencies and Xinhua contributed to this story.