What are Colorado gun laws for magazine capacity?

Colorado gun magazines may hold a maximum of fifteen (15) rounds.¹ Anything that holds more than 15 rounds is considered a large-capacity magazine (LCM), which is illegal in the state under CRS 18-12-302. Note that the 15-round LCM limit does not include any rounds in the firearm’s chamber.

Penalties for LCMs in Colorado

Possessing, transferring, or selling a large-capacity magazine is typically a class 2 misdemeanor. This carries:

• Up to 120 days in jail, and/or
• Up to $750 in fines.

Though if you possessed the LCM during the commission of a felony or crime of violence (as defined by CRS 18-1.3-406), then prosecutors would file more serious class 6 felony charges. Penalties include:

• 1 year to 18 months in Colorado State Prison, and/or
• $1,000 to $100,000 in fines.

Finally, it is a class 2 misdemeanor to manufacture high-capacity magazines without a legible permanent stamp or marking indicating that the LCM was made after July 1, 2013. The marking must be conspicuously engraved or cast upon the LCM’s outer surface. Violations are punished by:

• Up to 120 days in jail and/or
• Up to $750 in fines.²

Exceptions Where LCMs are Legal

In Colorado, having a large capacity magazine is permitted in any of the following four circumstances.

1. You owned the LCM on July 1, 2013, and maintained continuous possession of it (the “grandfather clause”).
2. You possess the magazine for the sole purpose of transporting it to an out-of-state entity on behalf of an LCM manufacturer within Colorado.
3. You are an employee of the government or armed forces (including law enforcement officers and county sheriffs) who bears a firearm in the course of your official duties.
4. You are an LCM manufacturer or licensed gun dealer who transfers or sells LCMs to either:
   1. A branch of the U.S. armed forces;
   2. A department, agency, or political subdivision of Colorado, or of any other state, or of the United States government;
   3. A firearms retailer for the purpose of firearms sales outside Colorado;
   4. A foreign national government that has been approved by the U.S. government for transfer of LCMs; or
   5. An out-of-state transferee who may legally possess LCMs.

If your defense to LCM charges is that you are “grandfathered” in because you maintained possession since July 1, 2013, prosecutors bear the burden to prove otherwise beyond a reasonable doubt.³ Also, Colorado gun stores may still sell magazine part kits to repair and maintain lawfully-owned LCMs. However, you may not use the kit to assemble a new LCM.

History of Colorado’s LCM Ban

On July 20, 2012, a gunman shot and killed 12 people – and injured dozens more – in an Aurora movie theater. The gunman used a magazine that held 100 rounds of ammunition. A year after the Aurora Theater Shooting, Gov. John Hickenlooper signed House Bill 13-1224 limiting magazines to 15 rounds. Lawmakers – including Senate Democrat Sen. Rhonda Fields – meant to prevent further mass shootings and promote public safety through gun control. The new law was also supported by Attorney General Phil Weiser. This large-capacity magazine ban was challenged by the Rocky Mountain Gun Owners (a nonprofit organization with Republican leanings). However, the Colorado Supreme Court upheld it nearly eight years later on June 29, 2020. The court stated:

“Plaintiffs failed to prove beyond a reasonable doubt that HB 1224 violates the state constitutional right to bear arms…HB 1224 was a reasonable exercise of the police power that has neither the purpose nor effect of nullifying the right to bear arms in self-defense.”⁴

Then three years later on October 26, 2023, Colorado Attorney General Phil Weiser – along with 18 other attorneys general – filed a brief arguing that Washington, D.C.’s limits on the sale and possession of LCM align with the Second Amendment.⁵ Other recent gun laws include that purchasers must pass a Colorado Bureau of Investigations (CBI) background check, even for private sales.⁶ Plus under the red flag law, police officers or family members may ask a judge to take away your guns if you are an extreme risk to others or yourself.⁷

Moving to Colorado with LCMs

The law does not specifically address whether it is legal to move to Colorado with LCMs you lawfully owned in your home state. The safest bet is not to bring them with you.

Additional Reading

For more in-depth information, refer to these scholarly articles:

• Regulating Assault Weapons and Large-Capacity Magazines for Ammunition – JAMA.
• Why the Civilian Purchase, Use, and Sale of Assault Weapons and Semiautomatic Rifles and Pistols, along with Large Capacity Magazines, Should Be Banned – N.Y.U. Journal of Legislation & Public Policy.
• Constitutional Law – Large-Capacity Magazine Bans and the Second Amendment – University of Arkansas at Little Rock Law Review.
• The Ban on Large-Capacity Magazines – The Toughest Gun Control Law in the Nation.
• Living Heller: Large-Capacity Magazine Bans and the Circuit Courts’ Search for Clarity on Second Amendment Constitutional Scrutiny – Suffolk University Law Review.

Also learn more about Colorado gun laws and assault weapons laws and concealed handgun laws.

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Legal References