How Federal Law Regulates Firearm Frames and Receivers

Under federal law, firearm frames and receivers are themselves firearms, which means every rule that applies to a complete gun — background checks, serial numbers, licensing, age limits, and interstate transfer restrictions — applies equally to these single components. A frame is the core structural part of a handgun; a receiver is the equivalent part of a rifle or shotgun. Because every other part of a gun can be purchased freely, these two carry the full weight of federal regulation. In March 2025, the Supreme Court confirmed the ATF’s authority to regulate them, including partially complete versions and parts kits.

What the Law Treats as a Frame or Receiver

Under 27 CFR § 478.12, a frame is the part of a handgun that houses the component designed to hold back the hammer or striker before firing. A receiver is the corresponding part of a rifle, shotgun, or other non-handgun weapon that houses the component designed to seal the breech before firing.¹ On modern designs where the fire-control and breech-sealing functions live in different housings, the ATF designates which specific part qualifies as the regulated component.

The definition reaches beyond finished parts. An unfinished piece that can be converted into a working frame or receiver without extraordinary effort falls under the same rules. The ATF weighs how long conversion takes, what tools and skills it requires, what additional parts are needed, how much it costs, and whether the process would destroy the item. Jigs, templates, drill bits, instructions, and marketing materials sold alongside a piece all count. A raw metal block is not a frame. A near-finished piece packaged with a jig and drill bits almost certainly is.¹

The same logic applies to parts kits. A kit containing everything needed to build a functional frame or receiver is classified as a firearm. Selling one without a serial number and without running a background check on the buyer violates the Gun Control Act.²

Who Can Buy One

You must be at least 21 to buy a frame or receiver from a licensed dealer. A bare frame or receiver is legally a “firearm” rather than a rifle or shotgun, so the handgun age limit applies. The minimum does not drop to 18 even when the receiver could only be built into a long gun.³

Residency matters too. Federal law generally bars a licensed dealer from selling a firearm to someone who lives in a different state. The exception that lets buyers pick up a rifle or shotgun over the counter out of state does not cover frames and receivers.⁴ Buying from an out-of-state dealer requires the seller to ship the part to a licensed dealer in your home state, where you complete the transfer.

Beyond age and residency, 18 U.S.C. § 922(g) prohibits certain categories of people from possessing any firearm, including a bare frame or receiver:

Anyone convicted of a crime punishable by more than one year in prison
Fugitives from justice
People who unlawfully use or are addicted to controlled substances
Anyone adjudicated as mentally incompetent or committed to a mental institution
Certain noncitizens, including those unlawfully present or admitted on most nonimmigrant visas
Anyone dishonorably discharged from the military
Former U.S. citizens who have renounced their citizenship
Anyone subject to certain domestic violence restraining orders
Anyone convicted of a misdemeanor crime of domestic violence

⁵

The ATF updated its definition of “unlawful user” of a controlled substance in January 2026 to require evidence of regular, ongoing use. Isolated incidents or a single failed drug test no longer support that determination.⁶

How the Purchase Works

When a licensed dealer sells a frame or receiver, the transaction follows the same process as any other firearm sale. You fill out ATF Form 4473, providing identification and answering eligibility questions under penalty of perjury. The dealer contacts the National Instant Criminal Background Check System, which searches federal databases for disqualifying records. The dealer cannot hand over the part until NICS returns a “proceed” response or the legally prescribed waiting period expires without a denial.⁷

On Form 4473, frames and receivers go in the “Other Firearm” box, not “Handgun” or “Long Gun.” That classification is what triggers the 21-year age requirement and blocks the out-of-state pickup exception, even for a receiver that would only ever become a rifle.⁷

Lying on Form 4473 is a separate federal felony from any underlying offense that made the buyer ineligible.

Because the rifle-and-shotgun exception does not apply, an interstate purchase always runs in two steps: the selling dealer ships to a licensed dealer in your state, and you complete the paperwork and background check locally. The receiving dealer typically charges a transfer fee, commonly in the $25 to $50 range, though fees vary. The U.S. Postal Service prohibits mailing handgun frames and receivers.⁸ Dealer-to-dealer shipments generally go through private carriers under those carriers’ own firearm policies.

Serial Numbers and Required Markings

Every frame or receiver produced by a licensed manufacturer or importer must carry permanent identification markings under 27 CFR § 478.92:

A unique serial number no other firearm from the same manufacturer shares
Manufacturer or importer name, or a recognized abbreviation
City and state of the place of business
Model designation, if one exists
Caliber or gauge

The serial number must be engraved, cast, or stamped to a minimum depth of 0.003 inches, with characters at least 1/16 of an inch tall, measured from the flat surface of the metal rather than from any raised edge left by stamping.⁹ These specifications are meant to keep markings from being sanded off later.

Polymer frames get their own accommodation. Because engraving plastic raises durability concerns, manufacturers may embed a permanent metal plate bearing the serial number into the polymer. The plate must be a permanent part of the frame, not a removable tag. Other methods can be approved by the ATF director case by case.¹⁰

Removing, altering, or defacing a serial number is a federal crime, as is knowingly possessing a frame or receiver whose serial number has been obliterated.

When You Need a License to Make or Sell

Anyone who manufactures or deals in frames and receivers as a business needs a Federal Firearms License. Two license types cover most activity:

Type 01 (Dealer) covers buying and selling firearms, including frames and receivers. The initial fee is $200 for three years, with $90 renewals every three years.
Type 07 (Manufacturer) covers producing firearms from raw materials or components. The fee is $150 for three years, with $150 renewals.

These fee amounts are set by statute.¹¹ Applying involves a background check, a physical inspection of the business premises, and verification that the location complies with local zoning.

The line between hobbyist and licensee is the “engaged in the business” standard. If you devote time and attention to manufacturing or dealing in firearms to predominantly earn a profit, you need a license. Making a single frame for a friend probably does not trigger the requirement. Regularly producing and selling them almost certainly does. Dealing or manufacturing without a required license is a federal felony carrying up to five years in prison.¹¹

Licensed dealers record every sale in an acquisition and disposition log, commonly called the “Bound Book,” and keep the records for the life of the business. Transfers between two licensed dealers do not require a Form 4473, though both parties still log the transfer.³

Making a Frame or Receiver for Yourself

Federal law does not prohibit an individual from making a firearm, including a frame or receiver, for personal use without an FFL. You do not need to add a serial number or register a personally made firearm as long as you are not in the business of manufacturing for sale or distribution. The firearm must be “detectable” under the Undetectable Firearms Act, meaning it must contain enough metal to trigger a standard security screening device, and you cannot be a prohibited person.¹²

The moment you transfer that firearm to someone else, the rules tighten. A private sale, a gift, or a trade means the piece needs to go through a licensed dealer (or be serialized by you, if you are one). Making frames regularly with the intent to sell them is what the ATF treats as being engaged in the business, and that required a manufacturer’s license before the first sale.

Licensed dealers and gunsmiths who take in a privately made firearm through a trade, repair, or any other acquisition must mark it with a serial number within seven days of receipt or before transferring it, whichever comes first. The markings must meet the same depth and character-size standards that apply to factory-produced firearms.¹²

Penalties

Because frames and receivers are legally firearms, every penalty that applies to a complete gun applies equally to them.

A prohibited person who possesses any firearm, including a bare frame or receiver, faces up to 15 years in federal prison under the enhanced penalties enacted by the Bipartisan Safer Communities Act. Someone with three or more prior convictions for violent felonies or serious drug offenses faces a mandatory minimum of 15 years with no possibility of probation.¹³

Dealers who fail to maintain proper records or run required background checks face administrative warnings, license revocation, or criminal prosecution depending on the severity and whether the violation appears willful. State laws may impose additional penalties on top of the federal ones.

The 2025 Supreme Court Ruling

The ATF’s updated frame-and-receiver rule (Final Rule 2021R-05F) took effect in August 2022 and drew immediate legal challenges from manufacturers and gun-rights groups, who argued the agency had exceeded its authority by regulating unfinished parts and weapons parts kits. In Bondi v. VanDerStok, decided March 26, 2025, the Supreme Court rejected that argument, holding that the Gun Control Act “plainly reaches some partially complete items” and that the rule is not facially inconsistent with the statute.¹⁴ Litigation continues on narrower issues, but the rule remains in effect and enforceable nationwide. Anyone buying, selling, or manufacturing frames and receivers should treat the current framework as settled law.

1
eCFR. 27 CFR 478.12 – Definition of Frame or Receiver
2
Bureau of Alcohol, Tobacco, Firearms and Explosives. Definition of Frame or Receiver and Identification of Firearms Overview
3
Bureau of Alcohol, Tobacco, Firearms and Explosives. Federal Firearms Licensee Quick Reference and Best Practices Guide
4
Bureau of Alcohol, Tobacco, Firearms and Explosives. Residency Requirements for Persons Acquiring Firearms
5
Office of the Law Revision Counsel. 18 US Code 922 – Unlawful Acts
6
Federal Register. Revising Definition of Unlawful User of or Addicted to Controlled Substance
7
Bureau of Alcohol, Tobacco, Firearms and Explosives. ATF Form 4473 – Firearms Transaction Record
8
United States Postal Service. Publication 52 – Hazardous, Restricted, and Perishable Mail
9
eCFR. 27 CFR 478.92 – Identification of Firearms and Armor Piercing Ammunition
10
ATF eRegulations. 27 CFR 478.92 – Identification of Firearms
11
Office of the Law Revision Counsel. 18 USC 923 – Licensing
12
Bureau of Alcohol, Tobacco, Firearms and Explosives. Privately Made Firearms
13
Office of the Law Revision Counsel. 18 USC 924 – Penalties
14
Supreme Court of the United States. Bondi v. VanDerStok, No. 23-852