A gun switch is a small machine gun conversion device that can make a semiautomatic pistol or rifle fire automatically.
The devices are also known as Glock switches, auto sears or drop-in auto sears, although the terminology can vary by firearm and design.
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A semiautomatic firearm generally fires one round with each pull of the trigger. A conversion device changes the firearm’s firing capability so it can fire more than one round with a single trigger function, without manually reloading between shots.
The Bureau of Alcohol, Tobacco, Firearms and Explosives says devices such as Glock switches and drop-in auto sears are machine gun conversion devices.
The agency says a conversion device is treated as a machine gun under federal law even when it is not attached to a firearm.
Why are gun switches illegal?
Federal law defines a machine gun to include not only a weapon that fires automatically, but also parts designed and intended to convert a weapon into a machine gun. That language appears in 26 U.S.C. § 5845(b). The definition is also incorporated into the federal firearms law at 18 U.S.C. § 921(a)(23).
The law is aimed at the function of the device, not just the firearm to which it might be attached. As a result, possessing a switch by itself can be treated as possessing a machine gun.
The federal prohibition became broader in 1986, when Congress passed the Firearms Owners’ Protection Act. Under 18 U.S.C. § 922(o), the transfer or possession of machine guns is generally prohibited, with limited exceptions for government-related activity and machine guns lawfully possessed before May 19, 1986, according to the Congressional Research Service.
Because gun switches are classified as machine guns, newly made or acquired devices generally do not fall within the exception for previously lawfully possessed machine guns. The ATF says possessing a machine gun conversion device without proper licensing is illegal under federal law.
What are the penalties?
A person convicted of knowingly violating the federal ban on machine gun possession can face a fine and up to 10 years in prison under 18 U.S.C. § 924(a)(2).
The ATF also warns that illegal possession of machine gun conversion devices can result in a prison sentence of up to 10 years. Other charges may apply if a device is used in connection with another crime.
Federal and state laws can differ, and state penalties may apply in addition to federal charges.
Anyone who finds or possesses a suspected conversion device should not handle or test it. The ATF advises people seeking to surrender a device to contact a local ATF office for instructions on safe disposal.
Why do authorities consider them dangerous?
A switch can substantially increase a firearm’s rate of fire, making it harder to control and increasing the risk that bullets will strike unintended people or property.
The ATF has also warned that the devices are small, can be deceptively marketed online and may be manufactured illegally, including through 3D printing.
In a January 2024 public service announcement, the ATF’s Los Angeles field division said it had recovered more than 31,000 machine gun conversion devices in the previous five years. The agency described the devices as illegal machine guns rather than ordinary gun accessories.
