The term ‘‘receiver’’ in 478.12(a)(2) 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.

The term ‘‘receiver’’ as stated in 478.12I 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 term 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 amended regulations examples that illustrate the definitions. 

The term “readily” as defined in 478.11 means a process, action, or physical state that is fairly or reasonably efficient, quick, and easy, but not necessarily the most efficient, speediest, or easiest process, action, or physical state. With respect to the classification of firearms, factors relevant in making this determination include the following: (1) Time, i.e., how long it takes to finish the process; (2) Ease, i.e., how difficult it is to do so; (3) Expertise, i.e., what knowledge and skills are required; (4) Equipment, i.e., what tools are required; (5) Parts availability, i.e., whether additional parts are required, and how easily they can be obtained; (6) Expense, i.e., how much it costs; (7) Scope, i.e., the extent to which the subject of the process must be changed to finish it; and (8) Feasibility, i.e., whether the process would damage or destroy the subject of the process, or cause it to malfunction.

The absence of a serial number is irrelevant in determining whether a weapon is a firearm.

Licensees may voluntarily request a determination whether a receiver is a regulated firearm by contacting ATF’s Firearms and Ammunition Technology Division (FATD).