(a) Except as otherwise provided in this section, the term “frame or receiver” means the following—

(1) The term “frame” means the part of a handgun, or variants thereof, that provides housing or a structure for the component (i.e., sear or equivalent) designed to hold back the hammer, striker, bolt, or similar primary energized component prior to initiation of the firing sequence, even if pins or other attachments are required to connect such component (i.e., sear or equivalent) to the housing or structure.

(2) The term “receiver” means the part of a rifle, shotgun, or projectile weapon other than a handgun, or variants thereof, that provides housing or a structure for the primary component designed to block or seal the breech prior to initiation of the firing sequence (i.e., bolt, breechblock, or equivalent), even if pins or other attachments are required to connect such component to the housing or structure.

(3) The terms “variant” and “variants thereof” mean a weapon utilizing a similar frame or receiver design irrespective of new or different model designations or configurations, characteristics, features, components, accessories, or attachments. For example, an AK-type firearm with a short stock (i.e., pistol grip) is a pistol variant of an AK-type rifle, an AR-type firearm with a short stock (i.e., pistol grip) is a pistol variant of an AR-type rifle, and a revolving cylinder shotgun is a shotgun variant of a revolver.

(4) The following are nonexclusive examples that illustrate the above definitions:

(i) Hinged or single framed revolvers: The frame is the part of the revolver that provides a structure designed to hold the sear.

(ii) Colt 1911, Beretta/Browning/FN Herstal/Heckler & Koch/Ruger/Sig Sauer/Smith & Wesson/Taurus hammer-fired semiautomatic pistols: The frame is the lower portion of the pistol, or grip, that provides housing for the sear.

(iii) Glock variant striker-fired semiautomatic pistols: The frame is the lower portion of the pistol, or grip, that provides housing for the sear.

(iv) Sig Sauer P250/P320 variant semiautomatic pistols: The frame is the internal removable chassis of the pistol that provides housing for the sear or equivalent component.

(v) Bolt action rifles: The receiver is the part of the rifle that provides a structure for the bolt.

(vi) Break action, lever action, or pump action rifles and shotguns: The receiver is the part of the rifle or shotgun that provides housing for the bolt, breechblock, or equivalent.

(vii) AK variant firearms: The receiver is the part of the weapon that provides housing for the bolt.

(viii) Steyr AUG variant firearms: The receiver is the central part of the weapon that provides housing for the bolt.

(ix) Thompson machineguns and semiautomatic variants, and L1A1, FN FAL, FN FNC, MP38, MP40, and SIG 550 firearms, and HK machineguns and semiautomatic variants: The receiver is the upper part of the weapon that provides housing for the bolt.

(x) Sten, Sterling, and Kel-Tec SUB-2000 firearms: The receiver is the central part of the weapon, or tube, that provides housing for the bolt.

(b) Firearm muffler or silencer frame or receiver. The terms “frame” and “receiver” shall mean, in the case of a firearm muffler or firearm silencer, the part of the firearm, such as an outer tube or modular piece, that provides housing or a structure for the primary internal component designed to reduce the sound of a projectile (i.e., baffles, baffling material, expansion chamber, or equivalent). In the case of a modular firearm muffler or firearm silencer device with more than one such part, the terms shall mean the principal housing attached to the weapon that expels a projectile, even if an adapter or other attachments are required to connect the part to the weapon. The terms shall not include a removable end cap of an outer tube or modular piece.

(c) Partially complete, disassembled, or nonfunctional frame or receiver. The terms “frame” and “receiver” shall include a partially complete, disassembled, or nonfunctional frame or receiver, including a frame or receiver parts kit, that is designed to or may readily be completed, assembled, restored, or otherwise converted to function as a frame or receiver, i.e., to house or provide a structure for the primary energized component of a handgun, breech blocking or sealing component of a projectile weapon other than a handgun, or internal sound reduction component of a firearm muffler or firearm silencer, as the case may be. The terms shall not include a forging, casting, printing, extrusion, unmachined body, or similar article that has not yet reached a stage of manufacture where it is clearly identifiable as an unfinished component part of a weapon (e.g., unformed block of metal, liquid polymer, or other raw material). When issuing a classification, the Director may consider any associated templates, jigs, molds, equipment, tools, instructions, guides, or marketing materials that are sold, distributed, or possessed with the item or kit, or otherwise made available by the seller or distributor of the item or kit to the purchaser or recipient of the item or kit. The following are nonexclusive examples that illustrate the definitions:

(d) Multi-piece frame or receiver. The term “multi-piece frame or receiver” shall mean a frame or receiver that may be disassembled into multiple modular subparts, i.e., standardized units that may be replaced or exchanged. The term shall not include the internal frame of a pistol that is a complete removable chassis that provides housing for the sear or equivalent component, unless the chassis itself may be disassembled. The modular subpart(s) identified in accordance with § 478.92 with an importer's or manufacturer's serial number shall be presumed, absent an official determination by the Director or other reliable evidence to the contrary, to be part of the frame or receiver of a weapon or device.

(e) Destroyed frame or receiver. The terms “frame” and “receiver” shall not include a frame or receiver that is destroyed. For purposes of these definitions, the term “destroyed” means that the frame or receiver has been permanently altered such that it may not readily be completed, assembled, restored, or otherwise converted to function as a frame or receiver. Acceptable methods of destruction include completely melting, crushing, or shredding the frame or receiver, or other method approved by the Director.

(f)(1) Frame or receiver classifications based on which part of the weapon was classified as such before April 26, 2022. Except as provided in paragraph (f)(2) of this section, the terms “frame” and “receiver” shall include the specific part of a complete weapon, including variants thereof, determined (classified) by the Director to be defined as a firearm frame or receiver prior to April 26, 2022. Any such part that is identified with an importer's or manufacturer's serial number shall be presumed, absent an official determination by the Director or other reliable evidence to the contrary, to be the frame or receiver of the weapon. The following is a nonexclusive list of such weapons and the specific part determined by the Director to be the firearm frame or receiver as they existed on that date:

(i) AR-15/M-16 variant firearms: The receiver is the lower part of the weapon that provides housing for the trigger mechanism and hammer (i.e., lower receiver).

(ii) Ruger Mark IV pistol: The frame is the upper part of the weapon that provides housing for the bolt or breechblock.

(iii) Benelli 121 M1 Shotgun: The receiver is the lower part of the weapon that provides housing for the trigger mechanism.

(iv) Vickers/Maxim, Browning 1919, M2, and box-type machineguns and semiautomatic variants: The receiver is the side plate of the weapon that is designed to hold the charging handle.

(2) Frame or receiver classifications of partially complete, disassembled, or nonfunctional frames or receivers before April 26, 2022. Prior determinations by the Director that a partially complete, disassembled, or nonfunctional frame or receiver, including a parts kit, was not, or did not include, a “firearm frame or receiver” under § 478.11, or “frame or receiver” under § 479.11 of this subchapter, as those terms were defined prior to April 26, 2022, shall not continue to be valid or authoritative after that date. Such determinations shall include those in which the Director determined that the item or parts kit had not yet reached a stage of manufacture to be, or include, a “firearm frame or receiver” under § 478.11, or “frame or receiver” under § 479.11 of this subchapter, as those terms were defined prior to April 26, 2022.