There are three major types of rapid-fire conversion devices:

• Auto sears, often in the form of “Glock switches,” alter the trigger mechanisms of semi-automatic pistols and rifles, enabling the guns to continuously fire rounds as long as the trigger is depressed and the gun has ammunition. These devices can allow pistols to fire at rates of up to 1,200 rounds per minute.¹U.S. Attorney’s Office for the Northern District of Texas, “Fort Worth Manufacturer Charged in Glock Switch Case,” press release, November 18, 2022, https://www.atf.gov/news/press-releases/fort-worth-manufacturer-charged-glock-switch-case. 
• Bump stocks are replacement shoulder attachments for semi-automatic rifles, particularly AR- and AK-style rifles, that harness the recoil from firing to allow a shooter to fire shots in rapid succession—up to 800 rounds per minute.²Michael Smith and Polly Mosendz, “The Making of a Millionaire and a Massacre,” Bloomberg, October 11, 2017, https://www.bloomberg.com/news/articles/2017-10-11/the-bump-stock-millionaire-and-the-las-vegas-massacre. 
• Binary and forced-reset triggers are drop-in replacement triggers for semi-automatic firearms, including AR- and AK-style firearms, that allow shooters to fire one shot when they pull the trigger and another when they release the trigger, effectively doubling the rate of gunfire.

The recoil caused by these devices can make the firearms equipped with them hard to control and shoot accurately, making them even more dangerous.

Nearly all of the firearms used by the mass shooter in Las Vegas were equipped with bump stocks, which enabled him to fire over 1,000 rounds of ammunition in minutes.³Of the 24 firearms recovered from the shooter’s hotel room, 15 were fired by the gunman. Of those 15 fired, 12 were AR-15s equipped with bump stocks. Las Vegas Metropolitan Police Department, “Criminal Investigative Report of the 1 October Mass Casaulty Shooting: LVMPD Event Number 171001-3519,” August 3, 2018, https://www.lvmpd.com/home/showpublisheddocument/134/638298568313170000. Following the shooting, states across the country—including those with Republican governors at the time⁴Massachusetts, Florida, Maryland, and Vermont.—enacted laws to prohibit bump stocks. The ATF also took steps to prohibit the manufacture, sale, and possession of bump stocks through a rule clarifying that the federal definition of “machine gun” includes bump stocks. The rule took effect in March 2019.⁵US Department of Justice and Bureau of Alcohol, Tobacco, Firearms and Explosives, “Bump-Stock-Type Devices,” Federal Register 83, no. 246 (December 26, 2018): 66514–54, https://www.govinfo.gov/content/pkg/FR-2018-12-26/pdf/2018-27763.pdf. Unfortunately, in its dangerous June 2024 decision in Garland v. Cargill, the Supreme Court threw out the ATF rule.⁶Garland et al. v. Cargill, 602 U.S. ____ (2024), https://www.supremecourt.gov/opinions/23pdf/22-976_e29g.pdf. While 16 states and Washington, DC, have specific and clear prohibitions on bump stocks under state laws, the Supreme Court’s decision in Cargill effectively legalized bump stocks in as many as 34 states.⁷Some of these states have laws prohibiting machine guns that could be interpreted to include bump stocks, but the laws do not explicitly state bump stocks are prohibited.

While some states have prohibited auto sears and similar conversion devices under laws related to machine guns for years, other states—including those with majority-Republican legislatures or Republican governors⁸Indiana, Mississippi, and Virginia.—have recently taken action to codify such prohibitions. 

Prohibiting rapid-fire conversion devices would help prevent people from using them to convert semi-automatic weapons into machine guns and address the growing threat of automatic gunfire and the mass shootings carried out with firearms equipped with these deadly devices.