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Auto sears explained: How one small device turns handguns, rifles into machine guns

In 2021, there were more than 200 shootings that had automatic gunfire.

WASHINGTON — It started as a pleasant, sunny Friday afternoon along Connecticut Avenue in Northwest D.C. People wrapped up their work weeks and students at the Edmund Burke School prepared to dismiss for the weekend.

Suddenly, a barrage of gunfire rained down from a 5th-floor apartment window. Within minutes, more than 200 rounds of bullets scattered across Connecticut Avenue.  As people ran for cover, police and paramedics responded. 

But a question hung in the air: in a country where automatic weapons are basically illegal, how did the alleged shooter, Raymond Spencer, fire more than 200 rounds in a matter of minutes?

RELATED: 'I wish I knew why' | DC Police provide first major update on investigation into 'sniper-style' shooting

Credit: DC police
Evidence picture from Raymond Spencer's apartment.


WUSA9 took the question to ATF Assistant Special Agent In Charge Chris Amon.

“It's just this small device that is able to convert that firearm from semi-automatic to fully automatic,” he said. “It’s one pull of the trigger and you can empty an entire magazine in two to three seconds.”

Credit: Ruth Morton/WUSA
Assistant Special Agent in Charge Chris Amon sits down with WSUA9's Matt Gregory

That device is called an auto sear. On the streets it’s referred to as a "switch." But, most commonly they are used in handguns like Glocks, which gives it the term “glock switch.”

According to the ATF an auto sear works, "by applying force to the trigger bar to prevent it from limiting the weapon to firing only one round each time the trigger is depressed.” One simple slip-in of the device and the gun becomes fully automatic. 

Credit: DC Police
The small device on the back of this Glock-style gun is an 'auto sear.' It's commonly referred to by criminals as 'switch' or 'glock switch,' for its ability to turn any gun into a fully automatic weapon.


Amon said they are very easy to acquire.

“They can be 3D-printed, they can be made, coming from overseas, people can order them via the dark web," Amon said. "There's a lot of different ways that people are getting these. However, they are illegal because they constitute a machine gun.”

During the investigation of the Van Ness "sniper-style" shooting, DC Police said they found auto sears in several of the shooter’s rifles.

“When I say that so many more people could have been killed by this gunman, and the reckless behavior that was displayed here, that is not an understatement,” DC Police Chief Robert Contee said. "This really could have been a lot worse than what it was."

Credit: DC Police
Auto Sear installed in a rifle

The Van Ness gunfire gutted Northwest D.C. But the fact is that the automatic gunfire phenomenon has been all over the District.

According to the ATF, in 2021 there were more than 200 shootings involving automatic gunfire in D.C., averaging out to almost four a week. 

In 2019, DC police confiscated 14 auto sears. Two years later, that number jumped to 66. At the time of this reporting, police had taken 45 off the street in 2022.

But it didn’t use to be this way. According to Amon automatic gunfire used to be rare in city crime.

However, when any gun can be made automatic by simple modification, it creates an increasingly more deadly environment. It’s a problem that has law enforcement’s full attention.

“How do you prevent that?” Contee asked. “These are the things that are worrisome for community members, but also that keeps me up at night.”

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