Knowingly possessing a firearm whose serial number has been removed, obliterated, or altered is a federal felony under 18 U.S.C. § 922(k), punishable by up to five years in prison, a fine, or both. Most states add their own charges on top, and federal sentencing guidelines can push the actual prison time well above the base offense. Defaced firearm penalties apply whether or not you were the person who tampered with the number, and whether or not the gun was ever used in another crime.
The Federal Offense
Section 922(k) prohibits two things: knowingly shipping, transporting, or receiving a firearm with a removed or altered serial number across state lines or international borders, and possessing or receiving such a firearm if it has ever moved through interstate or foreign commerce.1Office of the Law Revision Counsel. 18 USC 922 – Unlawful Acts The second part is the one that catches people. The gun does not have to cross state lines while you own it. If the manufacturer shipped it across a border at any point in its history, the interstate commerce element is satisfied.
The statute covers serial numbers that have been “removed, obliterated, or altered.” That includes grinding, stamping over, or scratching enough digits to make the number useless for tracing, not just complete removal.
Prison Time and Sentencing Enhancements
A conviction under § 922(k) carries a statutory maximum of five years in federal prison, a fine, or both.2Office of the Law Revision Counsel. 18 USC 924 – Penalties Actual sentences are shaped by the U.S. Sentencing Guidelines, which add a four-level enhancement when a defendant possessed a firearm whose serial number was rendered illegible to the unaided eye.3United States Sentencing Commission. Amendment 828 Four levels is significant. Depending on criminal history, it can translate into months or years of additional prison time.
The “unaided eye” standard has a practical edge. If the number is scratched but still readable without magnification or chemical treatment, the enhancement may not apply, even if the tampering is obvious.
The Knowledge Requirement
Section 922(k) uses the word “knowingly.” The government generally must prove the defendant knew they possessed a firearm and knew the serial number had been tampered with.1Office of the Law Revision Counsel. 18 USC 922 – Unlawful Acts You do not need to be the person who removed the number, and you do not need any plan to use the gun in another crime. Awareness alone is enough.
That has real consequences for anyone buying used. If you pick up a gun at a flea market, from a private seller, or through any channel that does not involve a licensed dealer checking the serial number, and the number turns out to be ground off, you are holding a federal felony. “I didn’t look closely” is a thin defense once a prosecutor shows the defacement was visible.
State Penalties
Nearly every state has its own law criminalizing possession of a firearm with a removed serial number, and many separately criminalize the act of removing the number. Classifications range from misdemeanors to serious felonies, with maximum prison terms typically running from about sixteen months to seven years depending on the state. Some states treat the offense as stand-alone; others use it as a sentencing enhancement on the underlying charge that brought the gun to law enforcement’s attention. Because state charges can be filed alongside federal ones, a single defaced firearm can expose you to prosecution in two court systems.
Antique Firearms Are Outside the Rule
Federal law defines an “antique firearm” as one manufactured in or before 1898, along with certain replicas that do not use modern fixed ammunition and muzzle-loading firearms designed for black powder.4Office of the Law Revision Counsel. 18 USC 921 – Definitions Antiques are generally excluded from the federal definition of “firearm” under the Gun Control Act, so § 922(k) does not reach them. A 19th-century revolver without a serial number is not a defaced firearm; it was made before serial numbers were required.
The exception is narrow. It does not cover weapons using modern rimfire or centerfire ammunition unless that ammunition is no longer commercially manufactured, and any gun built on a modern frame or receiver falls outside the exemption regardless of the age of its other parts.4Office of the Law Revision Counsel. 18 USC 921 – Definitions
Privately Made Firearms and Ghost Guns
Home-built firearms sit in a different corner of the law. A person who manufactures a firearm strictly for personal use has no federal obligation to add a serial number, provided the gun is never sold or transferred.5Bureau of Alcohol, Tobacco, Firearms and Explosives. Privately Made Firearms An unserialized personal build is not the same thing as a defaced firearm, because no serial number was ever removed.
In 2022, ATF finalized Rule 2021R-05F, clarifying that partially complete frames and receivers, including many products sold as “80% kits,” qualify as regulated firearms.6Bureau of Alcohol, Tobacco, Firearms and Explosives. Definition of Frame or Receiver and Identification of Firearms – Final Rule 2021R-05F Licensed dealers who take in a privately made firearm must engrave it with a serial number within seven days or before transferring it, whichever comes first.5Bureau of Alcohol, Tobacco, Firearms and Explosives. Privately Made Firearms In March 2025, the Supreme Court upheld the rule in Bondi v. VanDerStok, finding that ATF’s definitions of “weapon,” “frame,” and “receiver” are not facially inconsistent with the Gun Control Act and that partially complete frames and weapon parts kits can fall within the statutory definition of a firearm.7Supreme Court of the United States. Bondi v. VanDerStok, No. 23-852 Commercially sold ghost gun kits are now subject to the same serialization and background check requirements as traditional firearms.
If You Find a Firearm With a Tampered Serial Number
Do not handle it further. Do not try to clean the area, restore the number, or inspect it closely. Any of that can damage forensic evidence and put you in the position of explaining why you were working on a defaced gun. Contact local law enforcement, tell them where and how you found it, and let trained personnel take it. The same goes if you realize after a private purchase that a firearm you bought has an obliterated serial number. Holding onto it while you think it over is not a legal gray area. It is a potential felony in your safe.