These devices are often illegally imported from abroad or created through 3D printing, and have been put to terrifying use by criminals because they can quickly be installed into a semiautomatic weapon without specialized tools or knowledge. 

Auto sears are small, illegal machine gun conversion devices that can be made out of plastic or metal and, when inserted into a firearm, allow it to fire continually with a single pull of the trigger. These devices are frequently called “Glock switches” because of their pervasive use on Glock pistols, which are uniquely easy to convert to automatic fire. 

Designed to be particularly easy to modify, auto sears prevent a firearm’s trigger bar—the part of the gun that prevents the firing pin from moving forward and which lowers when the trigger is pulled—from re-engaging after a single shot. As a result, a firearm with an auto sear installed operates as a machine gun, allowing an otherwise semiautomatic weapon to fire one to two dozen rounds per second, making them particularly deadly, especially when coupled with features like large capacity magazines.¹

Weapons modified with auto sears operate with overwhelming and rapid lethality:

• In 2019, a family was mistakenly targeted in a shooting using guns equipped with auto sears; four family members were killed and another six wounded in a matter of seconds.² 
• In 2021, one Houston police officer was killed and another was wounded while serving an arrest warrant when the suspect immediately opened fire on the officers. Because of an auto sear installed in his weapon, the suspect was able to fire 30 rounds at the officers in under three seconds.³
• In 2023, four people were killed and dozens more injured when 89 gunshots were fired into a birthday party in Alabama; at least one of the guns used by the perpetrators was a handgun modified with an auto sear.⁴
• In 2023, an 11-year-old boy was killed when 22 shots were fired from a passing car in “the blink of an eye”—something possible, law enforcement officials stated, because of the weapon being modified to fire like a machine gun.⁵

The danger of auto sears is magnified by the fact that they are relatively inexpensive to manufacture. These devices are often smuggled into the United States from abroad, including commonly from China and Russia. A 2019 investigation by ATF uncovered nearly 4,000 PayPal orders for auto sears from just a single exporter, suspected to be a Chinese company, that sold the devices for under $20 each.⁶

In recent years, largely unregulated 3D printing technology has allowed the blueprints for these deadly devices to be freely shared online, facilitating criminal activity:⁷ 

• In 2020, following the publication of these blueprints, two members of an extremist group advocating for civil war in the US were arrested for attempting to sell 3D-printed auto sears to a foreign terrorist group.⁸  
• Later that same year, a West Virginia man was charged with 3D printing and selling hundreds of auto sears to domestic extremists, including to a man who subsequently shot two police officers and two security guards in California, killing two of the four victims.⁹ 

Despite the existing federal prohibition on auto sears, equivalent state legislation remains critical. The lack of state-level laws can complicate enforcement of the federal prohibition and leave our communities especially vulnerable to any changes in federal law that would increase the accessibility of auto sears.

The ease with which auto sears can be created, along with a lack of clarity in current state law, has resulted in the use of auto sears increasing at least sixfold over the past seven years, including in mass shootings:¹⁰

• In 2023, law enforcement responding to a shooting at a 16th birthday party in Alabama that left 32 injured found a handgun equipped with an auto sear at the scene, along with over 80 shell casings.¹¹ 
• In 2024, nearly 100 shell casings—and a gun equipped with an auto sear—were recovered from a shooting that injured four at a party in Detroit.¹² 

Incidents like these have caused police across the country to highlight the proliferation of auto sears and the need to further address the unique dangers they pose, both to the public and to law enforcement officials.¹³ From 2017 to 2021, nearly 5,500 auto sears were recovered by the ATF, with the number recovered increasing drastically over time.¹⁴

Auto sears are considered machine guns under federal law, which defines “machinegun” to include: 

Additionally, the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) issued a decision further clarifying that the definition of “machinegun” includes auto sears,¹⁶ regardless of whether the auto sear is installed in a firearm. It is therefore illegal to possess, transfer, manufacture, or import auto sears, with limited exceptions.¹⁷ 
In 2024, the Supreme Court limited the definition of machine guns in its Garland v. Cargill decision, in which it held that bump stock devices are not considered machine guns under federal law. However, this decision will not impact the designation of auto sears as machine guns, with a footnote in the decision stating that an auto sear “permits a shooter to fire multiple shots while engaging the trigger only once. ATF has accordingly recognized that modifying a semiautomatic rifle or handgun with an auto sear converts it into a machine gun.”¹⁸

Twenty-three states and the District of Columbia have enacted their own bans on auto sears in addition to the federal prohibition. Those states are: California, Colorado, Connecticut, Delaware, Hawaii, Illinois, Indiana, Iowa, Louisiana, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Nevada, New Jersey, New York, North Carolina, Rhode Island, South Carolina, Virginia, Washington, and Wisconsin. 

Nine of these 23 states do not specifically designate auto sears as machine guns, but have nevertheless enacted bans specific to auto sears, or bans on a broader category of devices which include auto sears, such as “machine gun conversion devices” or “rapid fire trigger activators” (which may also include bump stocks). These laws exist either alongside state machine gun prohibitions or elsewhere in state statute:

• Illinois¹⁹
• Maryland²⁰
• Massachusetts²¹
• Michigan²²
• Minnesota²³
• Mississippi²⁴
• Nevada²⁵
• New York²⁶ 
• Virginia²⁷

Five of the 23 states also go further than federal law, defining a machine gun to include any part designed and intended for use in converting a weapon into a machine gun, even if that is not the sole or exclusive purpose of the part. This definition includes auto sears. Some of these state laws also prohibit dangerous or offensive weapons generally—a term that includes machine guns:

• Colorado²⁸
• Iowa²⁹
• North Carolina³⁰
• Rhode Island ³¹
• South Carolina³²

An additional eight of these 23 states, as well as the District of Columbia, mirror federal law, defining a machine gun to include any part “designed and intended solely and exclusively” for use in converting a weapon into a machine gun–a definition which encompasses auto sears. As a result, the following states’ restrictions on machine guns also apply to auto sears:

• California³³
• Connecticut³⁴
• Delaware³⁵
  District of Columbia³⁶, 
• Hawaii³⁷
• Indiana ³⁸
• Louisiana³⁹
• Washington⁴⁰
• Wisconsin⁴¹

Finally, New Jersey prohibits “any instrument or device adaptable for use as a machine gun.”⁴²

The scope of the laws in these states vary, and prohibit a combination of the possession, transfer, transport, use, manufacture, sell, or offer to sell auto sears.

• Statutes should prohibit the manufacture, sale, possession, transport, purchase, and use of auto sears, and should also prohibit their attemptedmanufacture, sale, possession, transport, purchase, and use.
• Prohibitions of auto sears should cover any part designed and intended for use in converting a weapon into a machine gun, even if that is not the sole or exclusive purpose of the part.
• Statutes should also ban bump stocks and other trigger activators.

1. Alain Stephens and Keegan Hamilton, “Auto Sears: The Return of the Machine Gun,” The Trace, March 24, 2022, https://www.thetrace.org/2022/03/auto-sear-gun-chip-glock-switch-automatic-conversion.[↩]
2. Alain Stephens and Keegan Hamilton, “Auto Sears: The Return of the Machine Gun,” The Trace, March 24, 2022, https://www.thetrace.org/2022/03/auto-sear-gun-chip-glock-switch-automatic-conversion.[↩]
3. Chloe Alexander and Marcelino Benito, “‘This is what we’re up against’ | HPD releases bodycam of two officers shot with gun rigged as mini machine gun,” KHOU 11, October 12, 2021, https://www.khou.com/article/news/crime/bodycam-video-released-bill-jeffrey-auto-switch/285-c4f49390-3580-4b48-9fba-6d007a45c012.[↩]
4. Kim Chandler, “Alabama police: 89 shots fired into crowded Sweet 16 party,” Associated Press, April 25, 2023, https://apnews.com/article/alabama-sweet-16-party-shooting-1f3435fc2c4666d5338ee15f4d03bb79.[↩]
5. Lindsay Whitehurst, “A surge of illegal homemade machine guns has helped fuel gun violence in the US,” Associated Press, March 9, 2024, https://apnews.com/article/machine-guns-modified-illegal-switches-gun-violence-ddc2e9b6602ee1eb62e75732bbd54784.[↩]
6. Scott Glover, “ATF on the hunt for thousands of illegal machine gun conversion devices smuggled into US,” CNN, May 23, 2019, https://www.cnn.com/2019/05/23/us/atf-agents-hunting-down-illegal-machine-gun-device-invs.[↩]
7. Champe Barton and Chip Brownlee, “What Are 3-D Printed Guns, and Why Are They Controversial?” The Trace, April 8, 2022, https://www.thetrace.org/2021/02/3d-printer-ghost-gun-legal-liberator-deterrence-dispensed.[↩]
8. Champe Barton and Chip Brownlee, “What Are 3-D Printed Guns, and Why Are They Controversial?” The Trace, April 8, 2022, https://www.thetrace.org/2021/02/3d-printer-ghost-gun-legal-liberator-deterrence-dispensed.[↩]
9. Azi Paybarah, “West Virginia Man Sold Machine Gun Conversion Devices to Extremists, US Says,” New York Times, November 18, 2020, https://www.nytimes.com/2020/11/18/us/boogaloo-machine-gun-sales-indicted.html.[↩]
10. US Attorney’s Office, Western District of Oklahoma, “United States Attorney and ATF Discuss Emerging Threat of Machinegun Conversion Devices,” November 29, 2023, https://www.atf.gov/news/press-releases/united-states-attorney-and-atf-discuss-emerging-threat-machinegun-conversion-devices.[↩]
11. Bill Hutchinson and Jennifer Vilcarino, “Machine-gun conversion device dubbed ‘Glock switches’ taking violence to the ‘next level’: Experts,” ABC News, June 12, 2024, https://abcnews.go.com/US/machine-gun-conversion-device-taking-violence-level-experts/story.[↩]
12. Bill Hutchinson and Jennifer Vilcarino, “Machine-gun conversion device dubbed ‘Glock switches’ taking violence to the ‘next level’: Experts,” ABC News, June 12, 2024, https://abcnews.go.com/US/machine-gun-conversion-device-taking-violence-level-experts/story.[↩]
13. Bill Hutchinson and Jennifer Vilcarino, “Machine-gun conversion device dubbed ‘Glock switches’ taking violence to the ‘next level’: Experts,” ABC News, June 12, 2024, https://abcnews.go.com/US/machine-gun-conversion-device-taking-violence-level-experts/story.[↩]
14. Bureau of Alcohol, Tobacco, Firearms, and Explosives, “National Firearms Commerce and Trafficking Assessment, Crime Guns, Vol. II, Pt. VII, 4 (Jan. 11, 2023), https://www.atf.gov/firearms/docs/report/nfcta-volume-ii-part-vii-recommendations/download.[↩]
15. 26 U.S.C. § 5845(b). See also 18 U.S.C. § 921(a)(24).[↩]
16. ATF Ruling 81–4.[↩]
17. 18 U.S.C. § 9224(a)(2).[↩]
18. Garland v. Cargill, 602 U.S. ____ n.4 (2024).[↩]
19. 720 Ill. Comp. Stat. 5/24-1.9.[↩]
20. Md. Code Ann., Pub. Safety § 5-101, see also Md. Code Ann., Crim. Law § 4-301.[↩]
21. An Act Modernizing Firearm Laws, 2024 Mass. Acts 135, Sections 26, 115.[↩]
22. Mich. Comp. Laws § 750.224e(1-2) (2023).[↩]
23. Minn Stat. § 609.67, subd. 1, 2 (2023).[↩]
24. Ms. Code Ann. § 97-37-39.[↩]
25. Nev. Rev. Stat. § 202.274 (2023).[↩]
26. N.Y. Penal Law § 265.10, see also N.Y. Penal Law §§ 265.00, 265.01-c.[↩]
27. Va. Code Ann. § 18.2-308.5:1.[↩]
28. Colo. Rev. Stat. §§ 18-12-101, 18-12-102.[↩]
29. Iowa Code §§ 724.1, 724.3.[↩]
30. N.C. Gen. Stat. § 14-409.[↩]
31. R.I. Gen. Laws § 11-47-8 (“device that when attached to a semi-automatic weapon allows full-automatic fire”.[↩]
32. S.C. Code Ann. §§ 23-31-310, 23-31-340.[↩]
33. Cal. Penal Code §§ 16880, 32625.[↩]
34. Conn. Gen. Stat. §§ 53-202, 53-206g.[↩]
35. Del. Code Ann. tit. 11, § 1444.[↩]
36. D.C. Code Ann. §§ 7-2501.01(10), 22-4514(a).[↩]
37. Haw. Rev. Stat. §§ 134-1, 134-8.[↩]
38. Ind. Code §§ 35-31.5-2-190, 35-47-5-8, 9; § 35-42-1-1.[↩]
39. La. Rev. Stat. Ann. §§ 40:1751, 40:1752.[↩]
40. Wash. Rev. Code §§ 9.41.190, 9.41.220.[↩]
41. Wis. Stat. §§ 941.25, 941.26.[↩]
42. N.J. Rev. Stat. § 2C:39-5(a).[↩]