Legal Definition of a Firearm

The term “firearm” means, in part: (A) Any weapon (including a starter gun) which will or is designed to or may readily be converted to expel a projectile by the action of an explosion; and, (B) the frame or receiver of any such weapon. See 18 U.S.C. § 921(a)(3).

Basic Firearm Types

• Pistol – designed to be held in one hand, short stock below line of bore, chamber integral with the barrel, double or single action, semi-automatic or single shot.
• Revolver – designed to be held in one hand, short stock below line of bore, double or single action, breechloading chambered cylinder (top break, loading gate, swing-out cylinder, or removable cylinder loading mechanisms).
• Rifle – designed to be fired from the shoulder, rifled bore, various types of action (semi-automatic, lever, bolt, pump, top break, or auto loading).
• Shotgun – designed to be fired from the shoulder, smooth bore, various types of action (bolt, top break, pump, or semi-automatic), various barrel types (single, double, over/under, side-by-side).

Required Markings on Firearms

• Serial number: Must appear on frame or receiver, cannot be duplicated by manufacturer
• Manufacturer name, city and state (or country of manufacture if imported into U.S.) or manufacturers name and abbreviated Federal Firearm Licensee (FFL) number (first three and last five digits with no dashes) as a serial number prefix, followed by a hyphen, then the unique serial number (*see explanation below).
• Model designation (if assigned)
• Caliber or gauge
• Importer name, city and state (for firearms manufactured outside the U.S.)

*Final Rule 2021R-05F was signed by the Attorney General on April 11, 2022 and became effective August 24, 2022.

Prior to Final Rule 2021R-05F, licensed manufacturers and importers were required to identify each firearm they manufactured or imported by placing a serial number on the frame or receiver.  In addition to the serial number, licensed manufacturers and importers were required to place the following markings on firearm: model (if designated), caliber or gauge, name of manufacturer or importer, city and state, and the name and country of the foreign manufacturer (when applicable).  These additional markings could be placed on either the frame, receiver, or the barrel.

Under Final Rule 2021R-05F, licensed manufacturers and importers are now required to identify each new firearm* (manufactured or imported) by placement of the serial number, name of licensee, and city and state of their place of business, on the frame or receiver in accordance with the regulations. These markings may no longer be placed on the barrel or pistol slide.  The remaining identification marks (model, caliber or gauge, foreign manufacturer, and country of manufacture (if applicable)) may continue to be placed on the frame or receiver, barrel, or pistol slide.

It should be noted that Final Rule 2021R-05F allows manufacturers and importers to continue to mark existing firearm designs in the same manner as they did before the effective date of the Final Rule.  Nearly all firearms that ATF classified - prior to issuance of the Final Rule - are grandfathered and may continue to be marked in the same manner as before the effective date of Final Rule 2021R-05F.

Properly Identifying a Firearm

The most common reason for a firearm trace to fail is an invalid or incomplete firearm description. It is essential to note all visible markings on the recovered firearm and to include that information in the trace request. It is possible that a firearm may have difficult to identify markings or after-market modifications, making accurate firearms identification challenging. Please do not hesitate to contact ATF for assistance in properly identifying a recovered firearm.