Colorado law on homemade firearms, often called “ghost guns,” changed in 2023. Since June 2, 2023, it has been a crime in Colorado to make the frame or receiver of a gun, including with a 3-D printer, unless you are a federally licensed firearm manufacturer. Since January 1, 2024, it has also been a crime to possess a gun, frame, or receiver that does not carry a serial number put on by a federal firearms licensee, with a few narrow exceptions. This page explains what the law says, who it covers, and the penalties.
Key Takeaways
- Colorado bans making a frame or receiver of a firearm, including with a 3-D printer, unless you are a federally licensed firearm manufacturer. The ban applies even if the gun is only for personal use.
- It is also a crime to possess, buy, sell, transfer, or transport an unfinished frame or receiver, or a gun, frame, or receiver without a serial number from a federal firearms licensee, unless an exception applies.
- A first offense is a class 1 misdemeanor. A second or later offense is a class 5 felony.
- Anyone who already owned a homemade gun without a serial number on June 1, 2023 had until January 1, 2024 to have a federal firearms licensee put a serial number on it.
- A federal firearms licensee can serialize a gun, frame, or receiver, and must run a background check before returning it.
What Colorado Law Provides
- Making a frame or receiver is banned. A person may not manufacture, or cause to be manufactured, “including through the use of a three-dimensional printer, a frame or receiver of a firearm.” The only exception is a federally licensed firearm manufacturer. C.R.S. 18-12-111.5(5)(a). This took effect June 2, 2023.
- Unfinished frames and receivers. Possessing or transporting an unfinished frame or receiver is a crime (effective January 1, 2024), and so is selling, offering to sell, transferring, or buying one (effective June 2, 2023). It is not an offense if the item is required by federal law to carry a serial number and a federal firearms licensee has put one on it. C.R.S. 18-12-111.5(1) and (2).
- Guns, frames, and receivers without a serial number. Possessing, buying, transporting, or receiving one is a crime (effective January 1, 2024), and so is selling, offering to sell, or transferring one (effective June 2, 2023). The exceptions include a gun that has been made permanently inoperable, an antique firearm as defined in federal law, and a gun made before October 22, 1968. C.R.S. 18-12-111.5(3) and (4).
- Guns made before the law. A person who owned, on the day before June 2, 2023, a gun, frame, or receiver that the person made and that had no serial number from a federal firearms licensee had to have one put on it no later than January 1, 2024. C.R.S. 18-12-111.5(5)(b).
- Serializing. A federal firearms licensee may put a serial number on a gun or on a finished or unfinished frame or receiver. Handing the item back counts as a transfer, so the licensee must run a background check first. If the transfer is denied, the licensee must surrender the item to a law enforcement agency. C.R.S. 18-12-111.5(7).
| Offense under C.R.S. 18-12-111.5 | Level | Sentencing range |
|---|---|---|
| First offense | Class 1 misdemeanor | Up to 364 days in jail, a fine of up to $1,000, or both (C.R.S. 18-1.3-501(1)(a.5)) |
| Second or later offense | Class 5 felony | 1 to 3 years in prison, with 2 years of mandatory parole (C.R.S. 18-1.3-401(1)(a)(V.5)(A)) |
The penalty is set by C.R.S. 18-12-111.5(6).
Overview of Firearm Regulations in Colorado
Firearm regulation in Colorado comes from both state and federal law. Colorado requires a background check for private firearm transfers between unlicensed parties, subject to several statutory exemptions (C.R.S. 18-12-112). A licensed gun dealer may not transfer a firearm until the Colorado Bureau of Investigation approves the transfer after any required background check (C.R.S. 18-12-112.5).
A person under 21 may not buy a firearm, with exceptions for on-duty members of the armed forces and peace officers (C.R.S. 18-12-112.5(1)(a.5) and C.R.S. 18-12-112(2)(f)). Colorado also requires firearms to be securely stored when not in use. Failing to do so, when the person knows or reasonably should know that a juvenile could get access without a parent’s permission or that a resident may not legally possess a firearm, is unlawful storage of a firearm, a class 2 misdemeanor (C.R.S. 18-12-114).
Understanding Homemade Firearms
Homemade firearms, often called “ghost guns,” are typically assembled from kits or individual parts, or made from scratch, sometimes with a 3-D printer. The feature that matters under Colorado law is the serial number. A gun, frame, or receiver without a serial number from a federal firearms licensee is the focus of C.R.S. 18-12-111.5.
Colorado’s definition of a “firearm” includes the frame or receiver of a firearm, and also includes a weapons parts kit that is designed to be, or may readily be, completed, assembled, restored, or otherwise converted to fire a projectile by the action of an explosive (C.R.S. 18-12-101(1)(b.7)). So an unassembled kit can be treated as a firearm.
Legal Requirements for Crafting Firearms
In Colorado, the main rule is simple: unless you are a federally licensed firearm manufacturer, you may not make the frame or receiver of a firearm. The sections below explain the key definitions, what the law requires instead of registration, and the penalties.
Definition of Homemade Firearms
Colorado law does not use the term “homemade firearm.” It uses the following defined terms, all found in C.R.S. 18-12-101(1):
| Term | What Colorado law says |
|---|---|
| Frame or receiver | The part of a firearm that is visible from the outside when the gun is assembled and that houses or holds one or more fire control components, such as the hammer, bolt, trigger mechanism, firing pin, or slide rails. Any part stamped with a serial number is presumed to be a frame or receiver. |
| Unfinished frame or receiver | “any forging, casting, printing, extrusion, machined body, or similar article that has reached a stage in manufacture when it may readily be completed, assembled, or converted to be used as the frame or receiver of a functional firearm,” or that is marketed or sold to become one. |
| Firearm | Includes the frame or receiver, and a weapons parts kit that can readily be completed or converted to fire. Does not include an antique firearm as defined in federal law. |
| 3-D printer | A computer-aided manufacturing device that builds a three-dimensional object from a digital model by layering and fusing resin or similar material. |
These definitions determine whether an item is covered by Colorado’s serial number law.
Registration and Licensing Requirements
Colorado law does not provide a registration process for homemade guns. What it requires instead is a serial number put on by a federal firearms licensee (C.R.S. 18-12-111.5(7)). Local governments, including law enforcement agencies, may not keep a list or database of people who buy or transfer firearms, or of the serial numbers of firearms bought or transferred (C.R.S. 29-11.7-102).
Local governments may, however, adopt their own laws governing the sale, purchase, transfer, or possession of firearms and firearm components, as long as those laws are not less restrictive than state law (C.R.S. 29-11.7-103). Check the rules of the city or county where you live.
Federal law separately makes it unlawful for anyone other than a licensed importer, manufacturer, or dealer “to engage in the business of importing, manufacturing, or dealing in firearms” (18 U.S.C. 922(a)(1)(A)). Colorado’s ban goes further: it applies to anyone who is not a federally licensed firearm manufacturer, whether or not the gun is made for sale.
Legal Penalties for Non-Compliance
Unlawful conduct involving an unserialized firearm, frame, or receiver is a class 1 misdemeanor, and a second or subsequent offense is a class 5 felony (C.R.S. 18-12-111.5(6)). A class 1 misdemeanor carries up to 364 days in jail and a fine of up to $1,000. A class 5 felony carries 1 to 3 years in prison.
Other charges can apply depending on the facts. Removing, defacing, covering, altering, or destroying a serial number is defacing a firearm, a class 1 misdemeanor (C.R.S. 18-12-104). Knowingly possessing a firearm whose serial number has been removed or altered is also a class 1 misdemeanor (C.R.S. 18-12-103).
Restrictions on 3D Printed Guns
Colorado law names 3-D printing directly. The ban on making a frame or receiver expressly includes making one “through the use of a three-dimensional printer” (C.R.S. 18-12-111.5(5)(a)). The definition of an unfinished frame or receiver also lists “printing” among the covered items (C.R.S. 18-12-101(1)(l)).
A 3-D printed gun therefore does not get around Colorado’s serial number requirement. Unless you are a federally licensed firearm manufacturer, printing a frame or receiver is itself the crime, and possessing an unserialized printed gun, frame, or receiver is a separate crime.
Federal law adds a rule about materials. It is unlawful to manufacture, import, sell, ship, deliver, possess, transfer, or receive a firearm that, after removal of grips, stocks, and magazines, is not as detectable by walk-through metal detectors as a federal test object, or whose major components do not show their true shape on airport x-ray machines (18 U.S.C. 922(p)).
Potential Consequences of Violating Firearm Laws
Violating Colorado’s homemade firearm law can lead to:
- Criminal Charges: A first offense under C.R.S. 18-12-111.5 is a class 1 misdemeanor. A second or later offense is a class 5 felony.
- Jail, Prison, and Fines: A class 1 misdemeanor carries up to 364 days in jail and a fine of up to $1,000. A class 5 felony carries 1 to 3 years in prison, with 2 years of mandatory parole.
- Loss of Firearm Rights: Federal law makes it unlawful for a person convicted of a crime punishable by more than one year in prison to possess a firearm (18 U.S.C. 922(g)(1)). A felony conviction for a second offense can therefore bring a federal ban on possessing guns.
Resources for Colorado Gun Owners
The statutes linked on this page are the primary source for Colorado’s rules on homemade firearms. The key section is C.R.S. 18-12-111.5, and the definitions are in C.R.S. 18-12-101.
If you have a gun, frame, or receiver without a serial number, a federal firearms licensee can serialize it under C.R.S. 18-12-111.5(7). Before handing it back, the licensee must run a background check. If you have already been contacted by police or charged, talk with a criminal defense lawyer before deciding what to do with the item.
Frequently Asked Questions
Can I Sell Homemade Firearms in Colorado?
Only in limited cases. Selling, offering to sell, or transferring a gun, frame, or receiver without a serial number from a federal firearms licensee is a crime in Colorado, as is selling or transferring an unfinished frame or receiver that has not been serialized (C.R.S. 18-12-111.5(2) and (4)). There are exceptions, including a sale to a federal firearms licensee and a temporary transfer to a licensee to have the item serialized. A private transfer of any firearm also requires a background check through a licensed gun dealer (C.R.S. 18-12-112), and federal law requires a license to be in the business of manufacturing or dealing in firearms (18 U.S.C. 922(a)(1)(A)).
Are There Age Restrictions for Making Firearms at Home?
In Colorado, making a frame or receiver is banned at any age unless you are a federally licensed firearm manufacturer (C.R.S. 18-12-111.5(5)(a)). Separately, a person under 21 may not buy a firearm, with exceptions for on-duty members of the armed forces and peace officers (C.R.S. 18-12-112.5(1)(a.5)). A person under 18 who knowingly possesses a handgun commits illegal possession of a handgun by a juvenile, a class 2 misdemeanor, and a class 5 felony for a second or later offense, subject to exceptions such as target shooting at an established range, hunting with a valid license, and being on a parent’s or grandparent’s property with a parent’s permission (C.R.S. 18-12-108.5).
Do I Need a License to Build a Firearm for Personal Use?
In Colorado, only a federally licensed firearm manufacturer may make a frame or receiver. The ban applies to everyone else, even if the gun is only for personal use (C.R.S. 18-12-111.5(5)(a)). Possessing a gun, frame, or receiver without a serial number from a federal firearms licensee is also a crime (C.R.S. 18-12-111.5(3)). Building a gun at home in Colorado without meeting these rules can lead to a criminal charge.
Can I Modify Existing Firearms Into Homemade Ones?
Some modifications are crimes in Colorado. Knowingly possessing a machine gun, a machine gun conversion device, a firearm silencer, a short rifle, or a short shotgun is possessing a dangerous weapon, a class 5 felony, unless an affirmative defense applies, such as holding a valid permit and license for the weapon (C.R.S. 18-12-102). Colorado defines a short rifle as one with a barrel under 16 inches or an overall length under 26 inches, and a short shotgun as one with a barrel under 18 inches or an overall length under 26 inches (C.R.S. 18-12-101(1)(h) and (i)). Removing or altering a serial number is defacing a firearm, a class 1 misdemeanor (C.R.S. 18-12-104). Making a new frame or receiver is covered by the ban in C.R.S. 18-12-111.5(5)(a).
Are There Specific Materials Prohibited for Homemade Firearms in Colorado?
Colorado’s serial number law does not depend on the material. Its definition of an unfinished frame or receiver covers “any forging, casting, printing, extrusion, machined body, or similar article” that can readily be completed as a frame or receiver (C.R.S. 18-12-101(1)(l)), so a metal, plastic, or 3-D printed frame is treated the same way. Federal law does restrict materials in one respect: a firearm that is not detectable by walk-through metal detectors, or whose major components do not show their true shape on airport x-ray machines, is prohibited (18 U.S.C. 922(p)).