Two men, holding seemingly identical Glock handguns, stand side-by-side in front of a silhouette-shaped target at an indoor shooting range. They aim their guns and open fire.

The man on the left squeezes the trigger 15 times, emptying his clip in a few seconds. The person on the right was able to empty one clip, reload, and empty another in the time it took the other to finish shooting. He only had to squeeze the trigger twice, one time for each magazine. The gun fired so rapidly it sounded like it was jet-fueled.

The men, agents with the Bureau of Alcohol, Tobacco, Firearms and Explosives, were demonstrating the sheer power of a handgun equipped with a tiny, quarter-sized accessory that converts it from a semi-automatic pistol to a fully automatic weapon.

Known as machine gun conversion devices, they’re typically made of metal or 3D-printed plastic, and render semi-automatic handguns capable of unleashing bullets at a rate of more than 1,000 per minute. They’re cheap, too, oftentimes marketed as keychains online and sold for less than $30, according to ATF officials.

And they are increasingly common on Baltimore’s streets.

Also known as auto sears, Glock switches, giggle switches and buttons, Baltimore Police recovered at least 59 in 2023, a review of a list of firearms the department seized last year shows. That’s more than five times as many as the department recovered in 2022, according to a Banner analysis of firearm recovery data. It’s possible more were recovered in 2022, but the department did not start formally tracking whether a firearm reviewed in its lab had a switch until 2023.

Neighboring jurisdictions report far fewer of the devices, but not all of them are keeping track. A Baltimore County Police spokesperson said the department doesn’t keep count, but noted officers have recovered them at crime scenes and when executing search warrants. Howard County Police have recovered four since the start of 2022.

In 2023, guns with auto sear switches were connected to assaults, carjackings, burglaries and at least two homicides in Baltimore. A gun with a Glock switch was used in the October shooting on Morgan State University’s campus that injured five people. Another was used in a high-profile shootout with police last summer.

On a warm, late June afternoon in East Baltimore, officers sought to arrest Darryl Gamble on an outstanding warrant for drug charges when Gamble started shooting at them in the 100 block of N. Milton Avenue. Gamble, 40, can be seen in security footage from the neighborhood wielding a handgun with a 51-round drum magazine attached.

That gun, a Glock 23, was equipped with a conversion device, according to a firearms operability report The Banner reviewed. Gamble managed to fire dozens of rounds at the officers, none of whom were injured, before they fatally shot him.

Zac Bergner lives a block from the shootout location and was in his basement when the shooting started. Although underground, the basement faces the street and has a small window, and Bergner said he could hear the sound of Gamble’s weapon, which didn’t register as gunfire at first because it was so rapid.

“Maybe jackhammers or sawing,” were his immediate thoughts. “It was a couple of long bursts.”

Nationally, the number of machine gun conversion devices being recovered by law enforcement has skyrocketed, with more than 5,400 recovered between 2017 and 2021, according to ATF figures. That’s nearly seven times more than police departments nationwide recovered from 2012 to 2016, according to the bureau.

The figures available in Maryland are almost certainly an undercount, as the devices often can’t be spotted unless someone racks the slide of a handgun and checks for them, ATF Special Agent and firearms examiner Matthew Leonard said. Usually, switches are installed by removing the back plate of a handgun and replacing it with the conversion device.

The device was patented in the 1990s by its inventor, Jorge Leon, a Venezuelan who developed it for use by police and military organizations. It did not catch on for government use and the patent expired in 2016.

Conversion devices found in the United States typically originate overseas, usually from China or Russia, or are 3D-printed. But, they can also be fastened out of everyday objects, like folded over razor blades, Leonard said.

Although they can be hard to detect, they’re easy to make and install. Leonard was able to 3D-print one in fewer than 45 minutes, using maybe $1-2 worth of filament, and install it without tools — ”I used a ballpoint pen,” he said.

The switches police recover are usually in guns with high-capacity magazines, meaning shooters have more bullets to fire. On average, guns with conversion devices in Baltimore have a magazine with a capacity of about 25 rounds — 15 more than the state limit for magazines sold or manufactured in Maryland, according to a Banner review of firearm recovery data.

Possessing a converted machine gun could give someone a sense of power, respect or street cred. It could also be borne out of a perceived necessity — if one’s rivals have a switch, not having one puts you at a disadvantage on the streets.

“Do you want to bring a semi-automatic pistol to a machine gun fight?” Leonard said. “It’s like taking a knife to a gunfight.”

What shooters gain in firepower they tend to lose in accuracy, Leonard said, because the constant rate of fire makes weapons harder to hold steady. Mix that in with high-capacity magazines and it increases the risk of bystanders being shot as part of someone else’s feud.

“Put bluntly, it’s spray and pray,” he said.

While machine gun conversion devices are illegal — the devices are classified federally as machine guns — Maryland does not criminalize their possession if they aren’t installed. In state courts, a person can be charged with possession of a rapid fire trigger activator or possession of a machine gun for an aggressive purpose. While still uncommon, those charges are being used more often as more switches are found.

In August, the Organized Crime Unit within the Maryland Attorney General’s Office indicted a group of people as part of an investigation into a Baltimore-area drug crew. That group, according to court records, used a luxury apartment at the Anthem House community in Locust Point as one of its stash houses.

When officers searched it in late July as part of a series of raids, they found, among other things, three handguns equipped with Glock switches, according to court records. Including the converted handguns, authorities seized more than two dozen firearms, body armor and more than 1,000 bullets from the Anthem House apartment, another luxury apartment downtown on Saratoga Street, and a storage unit in Baltimore County.

Indictments in that case list more than 170 counts for some individuals, including ones for possessing rapid fire trigger activators and machine guns.

Baltimore County Executive Johnny Olszewski Jr. and House Speaker Adrienne A. Jones, both Democrats, have taken notice of the dangers conversion devices pose and are supporting a bill to ban the production and possession of them in Maryland. Jones, whose district is in Baltimore County and who sponsors the bill, said the new law could serve as an additional tool for law enforcement. The bill passed out of committee on Friday, setting the measure up for a House vote.

“At the end of the day, automatic weapons have no place in our community,” Jones said at a Feb. 28 hearing.

Even if lawmakers pass a state ban on the devices, they aren’t necessarily going to be able to stop people from accessing the files to 3D-print them. That doesn’t mean lawmakers shouldn’t pursue that bill or others like it, said Cassandra Crifasi, co-director of the Johns Hopkins Center for Gun Violence Solutions and an assistant professor at the university.

Despite narratives to the contrary, policy, at least at the federal level, does work, Crifasi said. Congress has heavily regulated the sale of machine guns for nearly a century, after mobsters armed with them got into gun battles with cops during prohibition in the 1920s. The manufacture or importing of new machine guns for civilian use has been banned since 1986.

There are also strict regulations around the sale of suppressors, devices that muffle the sound of a gunshot. As a result, very few show up at crime scenes, Crifasi said.

Yet, 3D printing and other technological advancements threaten to change that.

“We’re not going to ban 3D printers” Crifasi, a gun owner who participates in pistol shooting competitions, said. “We need to do a better job of anticipating of where things will move next in terms of technology. We need to do a better job of raising the floor for everyone. States with strong gun laws are at the mercy of states with weaker gun laws around them.”