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Large capacity magazines are often used in mass shootings because they allow a shooter to keep firing many more rounds before stopping or pausing to reload, increasing casualties and reducing victims’ ability to escape or intervene.

Large capacity ammunition magazines are a common thread in many high-profile mass shootings in the United States. Because shooters with such magazines can fire at large numbers of people without taking the time to reload, those in the line of fire do not have a chance to escape, law enforcement does not have the chance to intervene, and the number of lives shattered by acts of gun violence increases dramatically.


Although the statutory definitions vary, magazines with a capacity of more than 10 rounds of ammunition are generally considered “large capacity” magazines.

higher death toll with large capacity magazines
An analysis of mass shootings between 1990 and 2017 found that attacks involving large capacity magazines resulted in a 62% higher death toll.


Louis Klarevas, Andrew Conner, and David Hemenway, “The Effect of Large–Capacity Magazine Bans on High–Fatality Mass Shootings, 1990–2017,” American Journal of Public Health 109, no. 12 (2019): 1754–1761.

While large capacity magazines are typically associated with semi-automatic assault weapons or machine guns, such devices can be used with any semi-automatic firearm that accepts a detachable magazine, including handguns.

Large capacity magazines (LCMs or LCAMs) have been used to perpetrate devastation on a massive scale in many high-profile mass shootings. In fact, large capacity magazines have been used in all ten of the deadliest mass shootings in the last decade. Large capacity magazines significantly increase a shooter’s ability to injure and kill large numbers of people quickly because they enable the individual to fire repeatedly without needing to reload.

The more rounds a shooter can fire consecutively, the more gunshot wounds they can inflict during an attack.

  • Mass shootings that involve large capacity magazines result in twice as many fatalities compared to mass shootings that do not involve high capacity magazines.1
  • Using an assault weapon and a drum magazine that held 100 rounds, the assailant in the 2019 Dayton, Ohio mass shooting, was able to fire at least 41 rounds of ammunition in less than 30 seconds, killing nine people and wounding 26 others.2
  • The shooter in the 2017 Las Vegas massacre was able to fire 100 rounds in just 10 seconds—without having to pause and reload—because he used a large capacity magazine, bump stock, and an assault rifle in his attack which killed 50 and injured hundreds.3

The time a shooter takes to reload his weapon can be critical in enabling victims to escape and law enforcement or others to intervene. When shooters have high capacity magazines, more bullets can be fired before this crucial time period for escape or other intervention.

  • The 2011 mass shooting in Tucson, AZ, where six people were killed and 13 others were wounded, including US Representative Gabrielle Giffords, was interrupted when the gunman stopped to reload his weapon and was tackled by a bystander.4
  • Similarly, during the 2018 shooting at Marjory Stoneman Douglas High School, students were able to escape down a stairwell while the shooter paused to reload his weapon.5

In addition to their role in mass shootings, firearms equipped with large capacity magazines significantly contribute to crime across the country. Alarmingly, data suggests that the use of firearms with large capacity magazines in crime has substantially increased since the expiration of the federal assault weapons and large capacity magazine ban in 2004.

  • Firearms equipped with high-capacity magazines are estimated to account for 22 to 36% of crime guns in most places.6
  • Estimates also suggest that nearly 40% of crime guns used in serious violent crimes, including murders of law enforcement officers, are equipped with high-capacity magazines.7
  • The share of recovered crime guns equipped with large capacity magazines increased by between 49 and 112% in several major cities—and an estimated 33% nationally—after the 1994 federal ban on assault weapons and large capacity magazines expired.8

A growing body of research shows that banning high-capacity magazines can help to prevent gun violence. In particular, studies have found that the federal ban on large capacity magazines helped to prevent violence and the use of high-capacity magazines in crime during the 10 years in which it was in effect.

  • During the 10-year period the federal assault weapons and large capacity magazine ban was in effect, mass shooting fatalities were 70% less likely to occur compared to the periods before and after the ban.9
  • While the federal assault weapons and large capacity ammunition ban was in effect, the number of high-fatality mass shootings fell by 37%, and the number of people dying in such shootings fell by 43%. When the ban lapsed in 2004, there was a 183% increase in high-fatality mass shootings and a 239% increase in deaths from such shootings.10

Polling consistently shows that a majority of Americans—nearly 70%—support laws that ban large capacity magazines.11

Summary of Federal Law

The Former Federal Ban

In 1994, Congress adopted the Violent Crime Control and Law Enforcement Act, making it unlawful to transfer or possess a “large capacity ammunition feeding device” not lawfully possessed on or before the law’s enactment.12 The law also banned the manufacture, transfer, and possession of semi-automatic assault weapons. See our summary on Assault Weapons for more information. The law was adopted with a sunset clause, however, and expired in 2004, despite overwhelming public support for its renewal. Thus, large capacity ammunition magazines and assault weapons that were formerly banned under the federal law are now legal unless banned by state or local law.

The 1994 Act defined “large capacity ammunition feeding device” as “a magazine, belt, drum, feed strip, or similar device…that has a capacity of, or that can be readily restored or converted to accept, more than 10 rounds of ammunition.”13 The ban contained a loophole, however, allowing for the continued transfer, and possession of large capacity ammunition magazines manufactured or possessed on or before enactment of the law.

Manufacturers took advantage of this loophole in the months leading up to the ban by boosting production of the magazines. As a result, they continued to be readily available—and legal—nationwide even during the time the 1994 Act was in effect, except where specifically banned by state or local law. Additionally, because most magazines do not have any identifying marks to indicate when they were manufactured, it was difficult to distinguish those made before or after the ban.14


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Effectiveness of the Ban

Despite these limitations, evidence indicates that the federal ban worked to reduce the use of large capacity magazines in crime. A Washington Post study analyzed data kept by the Virginia State Police and found a clear decline in the percentage of crime guns that were equipped with large capacity ammunition magazines after the federal ban was enacted.15 The percentage reached a low of 10% in 2004 and then steadily climbed after Congress allowed the ban to expire; by 2010, the percentage was close to 22%.16

Similarly, since the end of the federal ban, the Los Angeles Police Department has recovered significantly greater numbers of large capacity ammunition magazines, from 38 in 2003 to anywhere from 151 to 940 each year between 2004 and 2010.17

Bans on large capacity ammunition magazines—whether or not they contain legacy provisions that allow possession of previously owned LCMs—do not present a problem under The Takings Clause of the Fifth Amendment.

Summary of State Law

Fourteen states and the District of Columbia have enacted laws that generally ban the sale, manufacture, and other commerce or conduct with large capacity ammunition magazines. Those states are: California, Colorado, Connecticut, Delaware, Hawaii, Illinois, Maryland, Massachusetts, New Jersey, New York, Oregon, Rhode Island, Vermont, and Washington. Four of these states (DE, RI, OR, and WA) enacted these laws in 2022 and Illinois did so in January 2023. A majority of these jurisdictions also strongly regulate the sale and manufacture of assault weapons, which are commonly equipped with large-capacity magazines.

State Large Capacity Magazine Regulations
StateFor Use w/ Which Firearms Legal Magazine Capacity Limit Prohibited Acts for LCAMs
Treatment of Pre-Owned LCAMs
California18 All Firearms 10 rounds Manufacture, importation, keeping for sale, offering and exposing for sale, giving,  lending, and possession.19
Not allowed by a law that has not yet gone into effect.20
Colorado21 All Firearms 15 rounds Sale, transfer, and possession
Allowed (previously owned LCMs are exempt from ban)
Connecticut22 All Firearms 10 rounds Distribution, importation, keeping for sale, offering and exposing for sale, purchase, and possession
Allowed but must be registered.
Delaware23All Firearms17 roundsManufacture, sale, purchase, receipt, transfer, or possession
Not allowed (but CCW holders exempt)
D.C.24 All Firearms 10 rounds Possession, sale and other transfer
Not allowed
Hawaii25Handguns 10 rounds Manufacture, possession, sale, barter, trade, gift, transfer, and acquisition
Not allowed
Illinois26All Firearms10 rounds for Long Guns; 15 rounds for handguns Manufacture, sale, delivery, purchase, or causing another to manufacture, sell, or deliver, and possession
Allowed (previously owned or inherited LCMs are exempt from ban, but may only be used and possessed in limited locations or circumstances)
Maryland27 All Firearms 10 rounds Manufacture, sale, offering for sale, purchase, receipt, and transfer
Allowed (like all LCMs. There is no ban on possession.)
Massachusetts28 All Firearms 10 rounds Sale, offering for sale, transfer, and possession
Allowed (previously owned LCMs are exempt from ban)
New Jersey29 All Firearms 10 rounds Manufacture, transportation, shipment, sale, disposal, and possession
Not allowed (Certain firearms with magazines capable of holding 11-15 rounds could be registered until July 13, 2019)
New York30 All Firearms 10 rounds Manufacture, transportation, disposal, and possession
Not allowed
Oregon31 All Firearms10 roundsManufacture, sale, transfer, importation, use, possession, and purchase
Allowed (previously owned or inherited LCMs are exempt from ban, but may only be used and possessed in limited locations or circumstances)
Rhode Island32All Firearms10 roundsManufacture, sale, offer to sell, transfer, purchase, possession, and have under one’s control
Not allowed
Vermont33 All Firearms 10 rounds for Long Guns; 15 rounds for handguns Manufacture, sale, offering for sale, purchase, receipt, transfer, and possession
Allowed (previously owned LCMs are exempt from ban)
WashingtonAll Firearms10 roundsManufacture, import, distribution, and sale
Allowed, there is no ban on possession

Categories of Large Capacity Magazine Bans

For citations to these laws, please see the chart above.

Type of Firearm

Thirteen states and the District of Columbia generally ban the sale, manufacture, and other commerce or conduct in large capacity ammunition magazines for use with any firearm, while Hawaii’s law generally applies only to large capacity magazines designed for or capable of use with a handgun.

Definition of Large Capacity Magazine

Some state laws vary in which magazines they restrict as “large capacity magazines”: Of the 14 states that have enacted laws restricting large capacity magazines, the vast majority define a large capacity magazine as a magazine that is capable of holding more than 10 rounds of ammunition, and restrict those magazines accordingly. Four states have applied alternative definitions and restrictions to a smaller number of larger magazines, however:

Colorado defines a large capacity magazine as a magazine capable of holding more than 15 rounds and Delaware defines a large capacity as a magazine capable of holding more than 17 rounds. Vermont and Illinois restrict large capacity magazines that hold more than 10 rounds for use in a long gun or more than 15 rounds for use in a handgun.34

Prohibited Activities

of the deadliest mass shootings used LCMs
Large capacity magazines have been used in 10 out of 10 of the deadliest mass shootings in the last decade.


Based on data compiled by Giffords Law Center. Last updated July 2020.

California, Hawaii, New Jersey, and New York have the most comprehensive prohibitions, banning possession, manufacture, and transfer (including sale) of large capacity magazines.35 New Jersey allows possession of large capacity magazines by a person who has registered a legacy assault weapon and uses the magazine in connection with competitive shooting matches sanctioned by the Director of Civilian Marksmanship of the US Department of the Army.36

Other states ban various combinations of activities related to large capacity magazines. For instance, Colorado, Massachusetts, and the District of Columbia ban possession and transfer; Maryland bans manufacture and transfer; and Connecticut bans distribution, importation, purchase, transfer, and possession.

Legacy Magazines

State laws that ban the possession of large capacity ammunition magazines vary in their approach to large capacity magazines already in the possession of private individuals at the time a ban was adopted.

States that Do Not Exempt Legacy Large Capacity Magazines

California,37 Delaware,38 the District of Columbia, Hawaii,39 New Jersey, New York, and Rhode Island generally do not allow for continued possession of legacy large capacity magazines that were obtained before these states enacted bans on those magazines. As a result, these jurisdictions effectively required any large capacity magazine owned at the time the ban was enacted to be converted to a more limited capacity magazine, destroyed, or transferred to a dealer, law enforcement, or out of state.

States that Exempt Legacy Magazines

Connecticut’s law does not apply to large capacity magazines that were lawfully possessed before January 1, 2014, but lawful owners of such legacy magazines were required to register them with the State Department of Emergency Services and Public Protection within a specified period.

Colorado, Illinois, Massachusetts, Oregon, and Vermont all exempt possession of legacy large capacity magazines that were lawfully owned before the state enacted its LCM law.40 Oregon and Illinois provided clear limitations on the public use and carrying of these legacy magazines, however, generally requiring that legacy LCMs be carried and possessed only on private property or in specified locations such as licensed shooting ranges.

Maryland and Washington do not prohibit possession of large capacity magazines, although manufacture and transfer are banned. As a result, individuals who possessed such magazines before these states’ bans may continue to possess them.

States that Require Identification Markings for Magazines Manufactured after the LCM Law is Enacted

As noted above, enforcement of laws exempting pre-ban magazines is difficult because most magazines do not contain any markings to identify those that were manufactured before or after the effective date of the ban. As a result, the Colorado and Oregon laws require manufactures to include a permanent stamp or marking on all large capacity magazine produced after specified dates. These markings must indicate that the magazine was manufactured after the date the ban went into effect and must be conspicuously engraved or cast on the outer surface of the magazine.

Bans on “Conversion” or “Repair” Kits

In 2013, California explicitly banned the use of “conversion” or “repair” kits that allow the purchaser to construct home-made large capacity ammunition magazines from spare parts.

Key Legislative Elements

The features listed below are intended to provide a framework from which policy options may be considered. A jurisdiction considering new legislation should consult with counsel.

  • Definition of “large capacity ammunition magazine” includes magazines capable of holding more than 10 rounds 
  • Ban applies to large capacity ammunition magazines used with all firearm types
  • Restrictions generally apply to possession, sale, purchase, transfer, loan, transportation, distribution, importation, and manufacture of large capacity magazines 
  • Strong limitations on where and how legacy magazines may be carried and used to protect the public
  • If the manufacturing of large capacity magazines is permitted, all magazines manufactured after the adoption of the ban must be identified by distinct and legible markings
  • “Conversion” or “repair” kits that can be used to build large capacity ammunition magazines from spare parts are prohibited 


Gun violence is a complex problem, and while there’s no one-size-fits-all solution, we must act. Our reports bring you the latest cutting-edge research and analysis about strategies to end our country’s gun violence crisis at every level.

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  1. “Mass Shootings in the United States: 2009–2017,” Everytown for Gun Safety, December 2018,[]
  2. Holly Yan, Chuck Johnston, and Polo Sandoval, “The Dayton Gunman Killed 9 People by Firing 41 Shots in 30 Seconds. A High-Capacity Rifle Helped Enable That Speed,” CNN, August 5, 2019,[]
  3. Martha Bellisle, “High-Capacity Magazines Get New Scrutiny as Congress Returns,” ABC News, September 2, 2019,[]
  4. Griff Witte, “As Mass Shootings Rise, Experts Say High-Capacity Magazines Should be the Focus,” The Washington Post, August 18, 2019,[]
  5. Initial Report of the Marjory Stoneman Douglas High School Public Safety Commission, January 2, 2019,[]
  6. Christopher S. Koper et al., “Criminal Use of Assault Weapons and High–capacity Semiautomatic Firearms: an Updated Examination of Local and National Sources,” Journal of Urban Health 95, no. 3 (2018): 313–321.[]
  7. Id.[]
  8. See also, David S. Fallis and James V. Grimaldi, “VA Data Show a Drop in Criminal Firepower During Assault Gun Ban,” The Washington Post, January 23, 2011,[]
  9. Charles DiMaggio et al., “Changes in US Mass Shooting Deaths Associated with the 1994–2004 Federal Assault Weapons Ban: Analysis of Open–source Data,” Journal of Trauma and Acute Care Surgery 86, no. 1 (2019): 11–19.[]
  10. In this analysis, researchers defined high-fatality mass shootings as those in which six or more individuals were killed. Louis Klarevas, Rampage Nation: Securing America from Mass Shootings (Amherst, New York: Prometheus Books, 2016). See also, Christopher Ingraham, “It’s Time to Bring Back the Assault Weapons Ban, Gun Violence Experts Say,” The Washington Post, February 15, 2018,[]
  11. “Gun Policy Remains Divisive, But Several Proposals Still Draw Bipartisan Support,” Pew Research Center, October 18, 2018,[]
  12. 18 U.S.C. § 922(w)(1), (2). All references to sections of the Violent Crime Control and Law Enforcement Act of 1994, codified at 18 U.S.C. § 921 et seq., are to the sections as they appeared on September 12, 2004.[]
  13. 18 U.S.C. § 921(a)(31)(A). However, “attached tubular device[s] designed to accept, and capable of operating only with, .22 caliber rimfire ammunition” were exempted from the definition. 18 U.S.C. § 921(a)(31)(B).[]
  14. Importation of Ammunition Feeding Devices with a Capacity of More Than 10 Rounds, 61 Fed. Reg. 39, 320 (July 29, 1996) (amending 27 C.F.R. § 178.119).[]
  15. About the Project: The Hidden Life of Guns, Wash. Post, Jan. 22, 2011, at; David S. Fallis & James V. Grimaldi, Virginia Data Show Drop in Criminal Firepower During Assault Gun Ban, Wash. Post, Jan. 23, 2011, at[]
  16. Id.[]
  17. Press Release, Citizens Crime Commission of New York City, NYC & LA City Councils Introduce Rezo for Federal Ban on Large Capacity Ammunition Magazines 2 (Mar. 2, 2011), at[]
  18. Cal. Penal Code § 16350, 16740, 16890, 32310-32450.[]
  19. Cal. Penal Code § 32310. Note that while these provisions are still in effect, there is an ongoing lawsuit to challenge them, and in August 2020 a divided 3-judge panel of the Ninth Circuit appeals court determined that California’s LCM restrictions are unconstitutional. See Duncan v. Bonta, — F.3d — (9th Cir. 2021) (en banc).[]
  20. In 2016, California voters approved a ballot initiative, Proposition 63, which prohibited the possession of legacy large-capacity ammunition magazines and was slated to go into effect on July 1, 2017. However, enforcement of Proposition 63’s restrictions on possession of large-capacity magazines has been delayed pending an ongoing legal challenge by the NRA’s California affiliate. To learn more about this case and the Giffords Law Center’s work to defend Proposition 63, visit our Duncan v. Bonta page.[]
  21. Colo. Rev. Stat. §§ 18-12-301, 302, 303.[]
  22. Conn. Gen. Stat. §§ 53-202w, 53-202q.[]
  23. Del. Code Ann. tit. 11, § 1469(a).[]
  24. D.C. Code Ann. §§ 7-2506.01(b); 7-2507.06(a)(4).[]
  25. Haw. Rev. Stat. Ann. § 1348(c).[]
  26. 720 ILCS 5/24-1.10 (enacted January 10, 2023 by 2021 IL HB 5471.[]
  27. Md. Code Ann., Crim. Law § 4-305.[]
  28. Mass. Gen. Laws ch. 140, §§ 121, 131M.[]
  29. N.J. Stat. Ann. §§ 2C:39-1(y), 2C:39-3(j), 2C:39-9(h).[]
  30. N.Y. Penal Law §§ 265.00(23), 265.02(8), 265.10, 265.11, 265.20(7-f), 265.36-265.37.[]
  31. See 2022 Oregon Ballot Measure 114, SEC. 11.[]
  32. R.I. Gen. Laws §§ 11-47.1-2, 11-47.1-3(a). Federally licensed firearms dealers are exempt from these restrictions but it is generally unlawful for people who are not licensed firearms dealers to purchase large-capacity magazines, including from dealers.[]
  33. Vt. Stat. Ann. tit. 13, § 4021 (enacted by 2017 VT S 55, Sec. 8).[]
  34. Illinois’ assault weapons law also separately restricts as assault weapons any semiautomatic shotgun with a fixed magazine holding over 5 rounds of ammunition or that accepts any detachable magazine.[]
  35. Note that ongoing litigation has so far prevented California from ever enforcing its ban on possession of LCMs.[]
  36. Additional information on New Jersey’s assault weapon ban is contained in our summary on Assault Weapons.[]
  37. Note that ongoing litigation has so far prevented California from ever enforcing its ban on possession of LCMs.[]
  38. Delaware’s law allowed for continued possession by people who hold valid concealed carry permits[]
  39. When Hawaii enacted its law in 1992, it allowed individuals in possession of magazines that could accept 20 or fewer rounds to keep them for the following two years. This legacy provision expired in July 1, 1994, so individuals in possession of magazines that could accept more than 10 rounds were required to dispose of them before that date.[]
  40. Colorado’s law does not apply to magazines that were lawfully possessed before July 1, 2014;  Massachusetts’s exempts magazines that were lawfully possessed on September 13, 1994 (the date the federal ban took effect), Oregon’s exempts those that were lawfully possessed before the effective date of 2022 Oregon Ballot Measure 114 in November 2022, and Vermont’s law does not apply to magazines that were lawfully possessed before April 11, 2018).[]