California Firearm Precursor Part Identification Guidebook
California Firearm Precursor Part Identification Guidebook
California Firearm Precursor Part Identification Guidebook
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Introduction and Background
In 2019, the California Legislature passed Assembly Bill (“AB”) 879 (Ch. 730, Stats. 2019) to extend the laws governing
the sale and purchase of firearms and ammunition to firearm precursor parts. Pursuant to Penal Code section 16531, a
section added through the passage of AB 879, the Department of Justice (“Department”) is required to provide “written
guidance and pictorial diagrams demonstrating each category of firearm precursor part.” (Pen. Code, § 16531, subd. (b).)
In accordance with this mandate, the Department has developed this Firearm Precursor Part Identification Guidebook.
The purpose of this guidebook is to provide definitions of key terms and images that will allow an individual to properly
identify a firearm precursor part as it is defined under California law. Commencing July 1, 2022, the purchase or transfer
of a firearm precursor part must be performed through a licensed firearm precursor part vendor. (Pen. Code, § 30485.)
Furthermore, commencing July 1, 2022, the purchaser or transferee of a firearm precursor part must undergo an
eligibility check—or verify their exemption to an eligibility check—prior to receipt of the firearm precursor part. (Pen.
Code, § 30452.)
In an effort to ensure compliance with California law, this guidebook will aid vendors, prospective purchasers or
transferees, and law enforcement agencies with the identification of firearm precursor parts.
Please note that this guidebook is subject to change pending the implementation of related federal regulations.
(Definition of “Frame or Receiver” and Identification of Firearms, 86 Fed. Reg. 27720 (proposed May 21, 2021) (to be
codified at 27 C.F.R. parts 447, 478, 479).)
Term Definition
Firearm “Firearm” has the same meaning as the term is defined in Penal Code section 16520.
Firearm “Firearm precursor part” means a component of a firearm that is necessary to build or assemble a
Precursor Part firearm and is described in either of the following categories:
(1) An unfinished receiver, including both a single part receiver and a multiple part receiver, such as a
receiver in an AR-10- or AR-15-style firearm. An unfinished receiver includes a receiver tube, a molded
or shaped polymer frame or receiver, a metallic casting, a metallic forging, and a receiver flat, such as a
Kalashnikov-style weapons system, Kalashnikov-style receiver channel, or a Browning-style receiver
side plate. (Pen. Code, § 16531, subd. (a)(1).)
“Firearm precursor part” does not include: (1) firearm parts that can only be used on antique firearms,
as defined in Penal Code section 16170, subdivision (c) (Pen. Code, § 16531, subd. (c)); or (2) a firearm
or the frame or receiver thereof (Pen. Code, § 16531, subd. (d)).
Fire Control “Fire control component” means a component necessary for the firearm to initiate, complete, or
Component continue the firing sequence, including but not limited to any of the following: hammer, bolt, bolt
carrier, breechblock, cylinder, trigger mechanism, firing pin, striker, or slide rails. (Definition of “Frame
or Receiver” and Identification of Firearms, 86 Fed. Reg. 27720 (proposed May 21, 2021) (to be
codified at 27 C.F.R. parts 447, 478, 479).)
Handgun “Handgun” has the same meaning as the term is defined in Penal Code section 16640.
Long Gun “Long gun” has the same meaning as the term is defined in Penal Code section 16865.
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Term Definition
Machining “Machining” means the process of cutting, drilling, shaping, or removing material from a firearm
precursor part or firearm using a tool. (Cal. Code Regs, tit. 11, § 4302, subd. (a)(4).) (Definition of
“Frame or Receiver” and Identification of Firearms, 86 Fed. Reg. 27720 (proposed May 21, 2021) (to be
codified at 27 C.F.R. parts 447, 478, 479).)
Pistol “Pistol” has the same meaning as the term is defined in Penal Code section 16530.
Readily “Readily” means a process that is fairly or reasonably efficient, quick, and easy, but not necessarily the
most efficient, speedy, or easy process. Factors relevant in making this determination, with no single
one controlling, include the following:
(e) Availability, i.e., whether additional parts are required, and how easily they can be obtained;
(g) Scope, i.e., the extent to which the subject of the process must be changed to finish it; and
(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 may
readily be completed, assembled, converted, or restored to hold or integrate the fire control
components of a handgun or a long gun, the Department may consider any available instructions,
guides, templates, jigs, equipment, tools, or marketing materials. (Cal Code Regs., tit. 11, § 4302, subd.
(a)(5).) (Definition of “Frame or Receiver” and Identification of Firearms, 86 Fed. Reg. 27720 (proposed
May 21, 2021) (to be codified at 27 C.F.R. parts 447, 478, 479).)
Unfinished "Unfinished handgun frame" means a forging, casting, printing, extrusion, machined body or similar
Handgun article that has reached a stage in manufacture where it may readily be completed, assembled,
Frame converted, or restored to hold or integrate the fire control components of a handgun. (Cal. Code Regs.,
tit. 11, § 4302, subd. (a)(6).) (Definition of “Frame or Receiver” and Identification of Firearms, 86 Fed.
Reg. 27720 (proposed May 21, 2021) (to be codified at 27 C.F.R. parts 447, 478, 479).)
For additional guidance regarding unfinished handgun frames, please see the pictorial diagrams below.
Unfinished "Unfinished receiver" means a forging, casting, printing, extrusion, machined body or similar article
Receiver that has reached a stage in manufacture where it may readily be completed, assembled, converted, or
restored to hold or integrate the fire control components of a long gun. (Cal. Code Regs., tit. 11, §
4302, subd. (a)(7).) (Definition of “Frame or Receiver” and Identification of Firearms, 86 Fed. Reg.
27720 (proposed May 21, 2021) (to be codified at 27 C.F.R. parts 447, 478, 479.)
This includes both a single part receiver and a multiple part receiver (such as a receiver in an AR-10- or
AR-15-style firearm), a receiver tube, a molded or shaped polymer receiver, a metallic casting, a
metallic forging, and a receiver flat (such as a Kalashnikov-style weapons system, Kalashnikov-style
receiver channel, or a Browning-style receiver side plate). (Pen. Code, § 16531, subd. (a)(1).)
For additional guidance regarding unfinished receivers please see the pictorial diagrams below.
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Note: These pictorial diagrams represent some of the most commonly manufactured firearm precursor parts and
firearms. However, they do not represent all makes, models, or configurations of firearm precursor parts or firearms.
The machining that would be necessary to give this The machining of the Safety Selector Lever Hole, Hammer
unfinished Armalite (AR-15) style receiver a Safety Pin Hole and the Trigger Pin Hole on this Armalite (AR-15)
Selector Lever Hole, Hammer Pin Hole, or Trigger Pin style firearm receiver has been completed.
Hole has not been completed.
The machining that would be necessary to give this The machining of the Safety Selector Lever Hole, Hammer
unfinished Armalite (AR-15) style receiver a Safety Pin Hole and the Trigger Pin Hole on this Armalite (AR-15)
Selector Lever Hole, Hammer Pin Hole, or Trigger Pin style firearm receiver has been completed.
Hole has not been completed.
The machining that would be necessary to give this The machining of the Fire Control Cavity on this Armalite
unfinished Armalite (AR-15) style receiver a Fire Control (AR-15) style firearm receiver has been completed.
Cavity has not been completed.
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Armalite (AR-15) Style Receiver
Firearm Precursor Part (Unfinished Receiver) Firearm Receiver
The machining that would be necessary to give this The machining of the Trigger Slot on this Armalite (AR-15)
unfinished Armalite (AR-15) style receiver a Trigger Slot style firearm receiver has been completed.
has not been completed.
Summary of Determination Summary of Determination
The machining that would be necessary to give this The machining necessary to give this Armalite (AR-15)
unfinished Armalite (AR-15) style receiver the style firearm receiver the characteristics listed above has
characteristics listed above has not been completed. been completed. Therefore, the part is considered a
Therefore the part would be considered an unfinished firearm receiver.
receiver, and a firearm precursor part.
The machining of the 8 rivet holes that would be The machining of the 8 rivet holes which allow this
necessary to allow this unfinished Browning style receiver Browning style firearm receiver right side plate to be
right side plate to be attached to the bottom plate has not attached to the bottom plate has been completed.
been completed.
Summary of Determination Summary of Determination
The machining of the 8 rivet holes, which are used to The machining of the 8 rivet holes, which are used to
connect the unfinished Browning style right side plate to connect the Browning style right side plate to the bottom
the bottom plate, has not been completed. Therefore, this plate, has been completed. Therefore, the part is
part would be considered an unfinished receiver, and a considered a firearm receiver.
firearm precursor part.
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Kalashnikov (AK-47) Style Receiver Channel and Flat
Firearm Precursor Part (Unfinished Receiver) Firearm Receiver
The machining that would be necessary to give this The machining of the Trigger Pin Hole and Hammer Pin
unfinished Kalashnikov (AK-47) style receiver channel a Hole on this Kalashnikov (AK-47) style firearm receiver has
Trigger Pin Hole or a Hammer Pin Hole has not been been completed.
completed.
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Kalashnikov (AK-47) Style Receiver Channel and Flat
Firearm Precursor Part (Unfinished Receiver) Firearm Receiver
Summary of Determination Summary of Determination
None of the unfinished Kalashnikov (AK-47) style receivers The Kalashnikov (AK-47) style firearm receivers shown
shown above meet both of the following criteria: above meet both of the following criteria:
1. Receiver is in a channel configuration (bent or 1. Receiver is in a channel configuration (bent or
welded); and welded); and
2. The machining that is necessary to give this 2. The machining that is necessary to give this
receiver both a Trigger Pin Hole and a Hammer Pin receiver both a Trigger Pin Hole and a Hammer Pin
Hole has been completed. Hole has been completed.
If a receiver of this style does not meet both of these In this configuration the part would be considered a
criteria, the part would be classified as an unfinished firearm receiver.
receiver, and therefore a firearm precursor part.
This unfinished Heckler & Koch (HK) style receiver flat has
not yet been folded or rolled into a receiver channel
configuration. The welds that would be necessary to
integrate the fire control components of a firearm receiver
have not been completed.
This Heckler & Koch (HK) style firearm receiver has been
folded or rolled into a receiver channel configuration. The
welds necessary to attach the part to the fire control
components of a firearm have been completed.
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Heckler & Koch (HK) Style Receiver Flat
Firearm Precursor Part (Unfinished Receiver) Firearm Receiver
Summary of Determination Summary of Determination
The unfinished Heckler & Koch (HK) style receiver shown The Heckler & Koch (HK) style firearm receivers shown
above does not meet both of the following criteria: above meet both of the following criteria:
1. The receiver is in a channel configuration 1. The receiver is in a channel configuration
(bent/rolled); and (bent/rolled); and
2. The welds that are necessary to integrate the fire 2. The welds that are necessary to integrate the fire
control components of a firearm receiver have control components of a firearm receiver have
been completed. been completed.
In this configuration the part would be considered a
If a receiver of this style does not meet both of these
firearm receiver.
criteria, the part would be classified as an unfinished
receiver, and therefore a firearm precursor part.
This unfinished STEN style receiver tube has been The machining necessary to give this STEN style firearm
stenciled or overlaid with a blueprint identifying the receiver a Cocking/Charging Handle Slot, Ejection Port,
machining which would be necessary to give this receiver Sear Hole, and Magazine Well has been completed.
a Cocking/Charging Handle Slot, Ejection Port, Sear Hole,
or a Magazine Well. However, the machining of these
characteristics has not been completed.
Summary of Determination Summary of Determination
The unfinished STEN style receiver tube shown above has Whether it be through the use of a stencil, blueprint, or
been stenciled, or overlaid with a blueprint that would freehand, the machining necessary to give the receiver the
identify the machining necessary to give the receiver characteristics mentioned above has been completed.
characteristics mentioned above. However, if the Therefore, the part would be considered a firearm
machining that would be necessary to give the unfinished receiver.
receiver the characteristics mentioned above has not been
completed, then the part is considered an unfinished
receiver, and therefore a firearm precursor part.
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Glock Style Handgun Frame
Firearm Precursor Part (Unfinished Handgun Frame) Firearm Frame
The machining that would be necessary to give this The machining of the Trigger Housing Pin Hole, Trigger
unfinished Glock style handgun frame a Trigger Housing Pin Hole and Locking Block Pin Hole on this Glock style
Pin Hole, Trigger Pin Hole or Locking Block Pin Hole has handgun frame has been completed. The machining of the
not been completed. Additionally, the machining Slide Rail Tabs has also been completed to fit the Slide
necessary to remove the Slide Rail Tabs, which would be Rails.
necessary to fit the Slide Rails, has not been completed.
The machining that would be necessary to give this The machining of the Barrel Seat on this Glock style
unfinished Glock style handgun frame a Barrel Seat has handgun frame has been completed.
not been completed.
Summary of Determination Summary of Determination
The machining that would be necessary to give this The machining necessary to give this Glock style handgun
unfinished Glock style handgun frame the characteristics frame the characteristics listed above has been
listed above has not been completed. Therefore, the part completed. Therefore the part is considered a firearm
would be considered an unfinished handgun frame, and a frame.
firearm precursor part.
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1911 Style Handgun Frame
Firearm Precursor Part (Unfinished Handgun Frame) Firearm Frame
The machining that would be necessary to give this The machining of the Hammer Pivot Pin Hole, Sear Pivot
unfinished 1911 style handgun frame a Hammer Pivot Pin Pin Hole, and Slide Rails on this 1911 style handgun frame
Hole, Sear Pivot Pin Hole, or Slide Rails has not been has been completed.
completed.
The machining that would be necessary to give this The machining of the Barrel Seat and Barrel Lug areas on
unfinished 1911 style handgun frame a Barrel Seat or this 1911 style handgun frame has been completed.
Barrel Lug area has not been completed.
Summary of Determination Summary of Determination
The machining that would be necessary to give this The machining necessary to give this 1911 style handgun
unfinished 1911 style handgun frame the characteristics frame the characteristics listed above has been completed.
listed above has not been completed. Therefore, the part Therefore, the part is considered a firearm frame.
would be considered an unfinished handgun frame, and a
firearm precursor part.
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