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 senseless acts of gun violence increases dramatically.


Large capacity magazines, some of which can hold up to 100 rounds of ammunition, 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 time required to reload can be critical in enabling victims to escape and law enforcement or others to intervene.

Although the statutory definitions vary, magazines with a capacity of more than 10 rounds of ammunition are generally considered “large capacity” magazines. While large capacity magazines are typically associated with semi-automatic assault weapons or machine guns, such devices are generally available for any semi-automatic firearm that accepts a detachable magazine.

Mass Shootings

Large capacity ammunition magazines are a common thread uniting many of the high-profile mass shootings in America.1 The shooter who killed 20 children and 6 adults at Sandy Hook Elementary School in Newtown, CT, in 2012 equipped his assault weapon with 30-round magazines, which enabled him to fire 154 rounds in less than five minutes.2 The gunman in Tucson, AZ, who killed 6 people and injured 13 others, including US Representative Gabrielle Giffords, in a supermarket parking lot in 2011, used a handgun equipped with a 33-round magazine. His shooting spree was only interrupted when he was tackled by a bystander as he finally stopped to reload his weapon.3 Similarly, the man who killed 49 people and then himself in the Pulse nightclub in Orlando, Florida, in 2016 used a rifle with a 30-round magazine and a pistol with a 17-round magazine.4

Large capacity magazines were also used in the assault weapons massacres in a movie theater in Aurora, Colorado, in 2012; at Columbine High School in 1999; on a military base in Fort Hood, Texas, in 2009; and in an office building at 101 California Street in San Francisco in 1993.5 Moreover, the shooter who killed 67 people at a summer camp in Norway in 2011 stated in his written manifesto that he purchased 30-round ammunition magazines via mail order from a dealer in the United States.6

In fact, a review of 62 mass shootings between 1982 and 2012 by Mother Jones found that large capacity ammunition magazines were recovered in 50%.7 A review of mass shootings between January 2009 and January 2013 by Mayors Against Illegal Guns found that incidents where assault weapons or large capacity ammunition magazines were used resulted in 135% more people shot and 57% more killed, compared to other mass shootings.8

A New Phenomenon

Large capacity magazines are a relatively new phenomenon. Prior to the 1980s, the most popular type of handgun was the revolver, which typically holds six rounds of ammunition in a rotating cylinder. During the 1980s, however, the firearms industry began mass producing and marketing semiautomatic pistols, which can accept ammunition magazines.9 In 1980, semiautomatic pistols accounted for only 32% of the 2.3 million handguns produced in America.10 By 2008, however, such pistols accounted for 76% of the 1.8 million handguns produced that year.11

Comparison with Assault Weapons

Bans on large capacity ammunition magazines are often adopted in concert with bans on Assault Weapons. However, large capacity ammunition magazine bans reduce the capacity, and thus the potential lethality, of any firearm that can accept a large capacity ammunition magazine, including a firearm that is not an assault weapon.12 Crime data also suggests that a ban on large capacity magazines would have a greater impact on gun crime than a ban on assault weapons alone.13

Polling consistently shows that a strong majority of Americans support laws banning large capacity ammunition magazines. For example, in a 2012 survey for CNN, 62% of those polled supported such laws.14

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.15 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.”16 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.17

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.18 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%.19

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 2010.20

Bans on large capacity ammunition magazines—whether they contain grandfather provisions or not–do not present a problem under The Takings Clause of the Fifth Amendment.

Summary of State Law

Nine states and the District of Columbia have enacted laws banning large capacity ammunition magazines: California, Colorado, Connecticut, Hawaii, Maryland, Massachusetts, New Jersey, New York, and Vermont. All of these jurisdictions except Colorado and Vermont also ban assault weapons.


State that Bans LCAMs For Use w/ Which Firearms Legal Magazine Capacity Limit Prohibited Acts for LCAMs Treatment of Pre-Owned LCAMs
California21 All Firearms 10 rounds Manufacture, importation, keeping for sale, offering and exposing for sale, giving,  lending, and possession Not allowed by a law that has not yet gone into effect.22
Colorado23 All Firearms 15 rounds Sale, transfer, and possession Allowed (“grandfathered”)
Connecticut24 All Firearms 10 rounds Distribution, importation, keeping for sale, offering and exposing for sale, purchase, and possession Allowed but must be registered.
D.C.25 All Firearms 10 rounds Possession, sale and other transfer Not allowed
Hawaii26 Handguns Only 10 rounds Manufacture, possession, sale, barter, trade, gift, transfer, and acquisition Not allowed
Maryland27 All Firearms 10 rounds Manufacture, sale, offering for sale, purchase, receipt, and transfer Allowed (like all LCAMs. There is no ban on possession.)
Massachusetts28 All Firearms 10 rounds Sale, offering for sale, transfer, and possession Allowed (“grandfathered”)
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 may be registered until July 13, 2019)
New York30 All Firearms 10 rounds Manufacture, transportation, disposal, and possession Not allowed
Vermont31 All Firearms 10 rounds for Long Guns; 15 rounds for handguns Manufacture, sale, offering for sale, purchase, receipt, transfer, and possession Allowed (“grandfathered”)

Description of State Laws Banning Large Capacity Ammunition Magazines:
For citations to these laws, please see the chart above.

Large capacity ammunition magazine bans can be broken down into the following general categories:

States that Ban Large Capacity Magazines for Use with Any Firearm

Eight states (California, Colorado, Connecticut, Maryland, Massachusetts, New Jersey, New York, and Vermont) and the District of Columbia all ban large capacity ammunition magazines for use with any firearm.

State that Bans Large Capacity Magazines for Use with Handguns Only

Hawaii prohibits the manufacture, transfer, and possession of large capacity magazines designed for or capable of use with a handgun.

Definition of Large Capacity Magazine

State laws vary as to how the term “large capacity magazine” is defined: California, Connecticut, Hawaii, Maryland, Massachusetts, New Jersey, New York, and the District of Columbia define a large capacity magazine as a magazine that is capable of holding more than 10 rounds.32 Colorado defines a large capacity magazine as a magazine capable of holding more than 15 rounds. Vermont restricts 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.

Prohibited Activities

California, Hawaii, New Jersey, and New York have the most comprehensive prohibitions, banning possession, manufacture, and transfer (including sale) of large capacity magazines. New Jersey allows possession of large capacity magazines by a person who has registered a grandfathered 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.33

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.

Magazines Owned at the Time of the Ban

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 Grandfather Pre-Ban Magazines

California, the District of Columbia, Hawaii,34 New Jersey, and New York generally do not allow continued possession of 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. New York extends a 30-day grace period to any individual in possession of such a magazine manufactured before September 13, 1994, who is unaware that their magazine is illegal. This individual is not required to dispose of the magazine until he or she is notified by law enforcement or county licensing officials that possession is unlawful. Once they receive notice, they have 30 days to surrender or “lawfully dispose” of illegal magazines.

States that Grandfather Pre-Ban Magazines

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

Colorado, Massachusetts, and Vermont all grandfathered possession of large capacity magazines that were owned prior to the effective date of a ban.35

Maryland does 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 Law

As noted above, enforcement of laws grandfathering 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 law requires manufactures to include a permanent stamp or marking on all large capacity magazine produced after July 1, 2013. 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.

Selected Local Law

See the description in our summary on Assault Weapons of the Blair-Holt Assault Weapons Ban in Cook County, Illinois. This law includes a ban on large capacity ammunition magazines.

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 (Hawaii, California, Connecticut, Maryland, Massachusetts, New York, District of Columbia).
  • Ban applies to large capacity ammunition magazines for use with all firearms (California, Colorado, Connecticut, Maryland, Massachusetts, New Jersey, New York, Vermont, and District of Columbia).
  • Prohibited activities include possession, sale, purchase, transfer, loan, pledge, transportation, distribution, importation, and manufacture of large capacity ammunition magazines (California, Hawaii, New Jersey, and New York are the most comprehensive, banning manufacture, transfer, and possession).
  • No allowance for pre-ban magazines (California, District of Columbia, Hawaii, New Jersey, New York); alternatively, if pre-ban magazines are grandfathered, the owner must register them before a specified date (Connecticut).
  • 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 (Colorado).
  • “Conversion” or “repair” kits that can be used to build large capacity ammunition magazines from spare parts are prohibited (California).
  1. See Violence Policy Center, Mass Shootings in the United States Involving High-Capacity Ammunition Magazines, at ⤴︎
  2. Mary Ellen Clark & Noreen O’Donnell, Newtown School Gunman Fired 154 Rounds in Less than 5 Minutes, Reuters, Mar. 28, 2013, at ⤴︎
  3. Sam Quinones & Nicole Santa Cruz, Crowd Members Took Gunman Down, L.A. Times, Jan. 9, 2011, at ⤴︎
  4. Bart Jansen, Weapons gunman used in Orlando shooting are high-capacity, common, USA Today, June 15, 2016, at ⤴︎
  5. Id. For more information about these tragedies, see Mark Follman, Gavin Aronsen,& Deanna Pan, A Guide to Mass Shootings in America, Mother Jones (July 20, 2012), at ⤴︎
  6. Stephanie Condon, Norway Massacre Spurs Calls for New US Gun Laws, (July 28, 2011), at ⤴︎
  7. Mark Follman et al., More Than Half of Mass Shooters Used Assault Weapons and High-Capacity Magazines, Mother Jones (Feb. 27, 2013), at ⤴︎
  8. For some of the mass shootings included in the analysis, information about the types of firearms and ammunition magazines used remains unknown. Mayors Against Illegal Guns, Analysis of Recent Mass Shootings 1 (Jan. 2013), at ⤴︎
  9. Violence Policy Center, Backgrounder on Glock 19 Pistol and Ammunition Magazines Used in Attack on Representative Gabrielle Giffords and Others 1 (Jan. 2011), at ⤴︎
  10. Id. ⤴︎
  11. Id. at 2. ⤴︎
  12. As of 1994, 21% of civilian-owned handguns and 18% of all civilian-owned firearms were equipped with magazines that could hold 10 or more rounds. Christopher S. Koper, An Updated Assessment of the Federal Assault Weapons Ban: Impacts on Gun Markets and Gun Violence, 1994-2003, Report to the National Institute of Justice, US Department of Justice 6, 18 (June 2004), at Assault weapons make up only about 1% of the firearms estimated to be in civilian hands. Bureau of Justice Statistics Selected Findings, US Department of Justice, Firearms, Crime, and Criminal Justice: Guns Used in Crime 6 (July 1995), at ⤴︎
  13. In 1994, guns equipped with large capacity magazines were involved in 14 to 26% of gun crimes, while assault weapons were only used in 6%. Koper, supra note 11, at 19. Additionally, a survey of police departments conducted by the Police Executive Research Forum found that “38% of the police departments reported noticeable increases in criminals’ use of semiautomatic weapons with high-capacity magazines” since the expiration of the federal ban. Police Executive Research Forum, Guns and Crime: Breaking New Ground by Focusing on the Local Impact 2 (May 2010), at ⤴︎
  14. CNN/ORC International Poll, December 17-18 – Gun Rights 3 (Dec. 2012), at ⤴︎
  15. 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. ⤴︎
  16. 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). ⤴︎
  17. 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). ⤴︎
  18. 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 ⤴︎
  19. Id. ⤴︎
  20. 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 ⤴︎
  21. Cal. Penal Code § 16350, 16740, 16890, 32310-32450. ⤴︎
  22. In 2016, California voters approved a ballot initiative, Proposition 63, which prohibited the possession of pre-owned large-capacity ammunition magazines and was slated to go into effect on July 1, 2017. However, that effective date was delayed after a lawsuit challenging the new LCAM restrictions was filed and a district court entered a preliminary injunction blocking the new law from going into an effect until a final ruling is issued. See Duncan v. Becerra, 265 F. Supp. 3d 1106 (S.D. Cal. 2017), aff’d, No. 17-56081, 2018 U.S. App. LEXIS 19690 (9th Cir. Jul. 17, 2018) (unpublished). ⤴︎
  23. Colo. Rev. Stat. §§ 18-12-301, 18-12-303. ⤴︎
  24. Conn. Gen. Stat. §§ 53-202w, 53-202q. ⤴︎
  25. D.C. Code Ann. § 7-2506.01(b). ⤴︎
  26. Haw. Rev. Stat. Ann. § 1348(c). ⤴︎
  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. Vt. Stat. Ann. tit. 13, § 4021 (enacted by 2017 VT S 55, Sec. 8. ⤴︎
  32. A law New York adopted in 2013 would also prohibit the manufacture or sale of any magazine that can hold more than seven rounds, and the possession of any magazine that can hold more than seven rounds if it was obtained after January 15, 2013. However, this law has been suspended and will not go into effect without further legislative action. See 2013 N.Y. ALS 1 § 58, as amended by 2013 N.Y. ALS 57 Part FF § 4. As enacted, the law prohibits the possession of any magazine that is actually holding more than seven rounds, except at a shooting range. In December 2013, however, a federal district court struck down this provision as violating the Second Amendment, while upholding several other provisions of the state’s regulation of assault weapons and large capacity magazines. N.Y. State Rifle & Pistol Ass’n v. Cuomo, 2013 US Dist. LEXIS 182307 (W.D.N.Y. Dec. 31, 2013). ⤴︎
  33. Additional information on New Jersey’s assault weapon ban is contained in our summary on Assault Weapons. ⤴︎
  34. 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 grandfathering 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. ⤴︎
  35. 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), and Vermont’s law does not apply to magazines that were lawfully possessed before April 11, 2018). ⤴︎