Cal. Code Regs. tit. 11, § 4303
(a) For purposes of this chapter, the following definitions apply:
(2) “Firearm precursor part” means any forging, casting, printing, extrusion, machined body or similar article:
(B) that is marketed or sold to the public to become or be used as the frame or receiver of a functional firearm once completed, assembled or converted.
“Firearm precursor part” does not include firearm parts that can only be used on antique firearms, as defined in Penal Code section 16170, subdivision (c).
(3) “Frame” means the part of a handgun, or variants thereof, that provides housing or a structure for the primary energized component designed to hold back the hammer, striker, bolt, or similar component prior to initiation of the firing sequence (i.e., sear or equivalent), even if pins or other attachments are required to connect such component to the housing or structure.
For a split or multiple part frame design, “frame” instead means the part of a handgun, or variants thereof, that has been designated as the frame by the federal Bureau of Alcohol, Tobacco, Firearms, and Explosives in subdivision (f)(1) of section 478.12 of Title 27 of the Code of Federal Regulations (August 2022), hereby incorporated by reference. One example includes the Ruger Mark IV pistol, in which the frame is the upper part of the weapon that provides housing for the bolt or breechblock.
(5) “Readily” 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 firearm precursor parts, factors relevant in making this determination include the following:
(H) Feasibility, i.e., whether the process would damage or destroy the subject of the process, or cause it to malfunction.
In determining whether a forging, casting, printing, extrusion, machined body, or similar article has reached a stage in manufacture where it may readily be completed, assembled, or converted to be used as the frame or receiver of a functional firearm, the Department may consider any available instructions, guides, templates, jigs, equipment, tools, or marketing materials.
(6) “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.
For a split or multiple part receiver design, “receiver” instead means the part of a rifle, shotgun, or projectile weapon other than a handgun, or variants thereof, that has been designated as the receiver by the federal Bureau of Alcohol, Tobacco, Firearms, and Explosives in subdivision (f)(1) of section 478.12 of Title 27 of the Code of Federal Regulations (August 2022), hereby incorporated by reference. Some examples include the following: (1) for AR-15/M16 variant firearms, the receiver is the lower part of the weapon that provides housing for the trigger mechanism and hammer (i.e. lower receiver); (2) for a Benelli 121 M1 Shotgun, the receiver is the lower part of the weapon that provides housing for the trigger mechanism; and (3) for 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.
Note: Authority cited: Section 16531, Penal Code. Reference: Sections 16519, 16520, 16531, 30400, 30401, 30420 and 30425, Penal Code; and Section 6215, Family Code.
1. New section filed 9-21-2022; operative 9-21-2022. Submitted to OAL for filing and printing only pursuant to Assembly Bill 1621, sections 39 and 41 (Stats. 2022, c. 76) (Register 2022, No. 38).