Penal Code § 16520 PC – Definition of a “Firearm”

In everyday conversation, words like "gun," "pistol," or "weapon" are used interchangeably. However, under California criminal law, a very specific legal definition dictates what does—and does not—constitute a firearm.

California Penal Code § 16520 PC establishes the foundational definition of a "firearm" used throughout the state's entire penal code.

This statute is incredibly important because scores of other gun charges—ranging from felon-in-possession laws to severe firearm sentencing enhancements—rely entirely on the legal definition established here.

Quick Reference Summary

Technical & Legal Attributes	Statutory Definition & Exclusions (PC 16520)
Primary Mechanism	Expulsion of a projectile through a barrel via explosion or combustion.
Inclusions (Operational)	Handguns, pistols, revolvers, rifles, shotguns, and digital/CNC-milled frames.
Inclusions (Component)	The frame or receiver of a weapon (even if completely disassembled).
Precursor / Ghost Guns	Includes firearm precursor parts and unfinished, readily convertible receivers.
Heavy Weapon Inclusions	Rockets, rocket-propelled projectile launchers, and explosive devices.
Statutory Exclusions	Unloaded antique firearms and authorized destructive devices.

What the Law Considers a "Firearm" (Plain English)

Under Penal Code 16520(a) PC, a firearm is explicitly defined as:

"...a device, designed to be used as a weapon, from which is expelled through a barrel, a projectile by the force of an explosion or other form of combustion."

To meet this standard, three specific criteria must be met simultaneously:

Designed as a Weapon: The item must be engineered to function as a weapon.
Has a Barrel: The projectile must pass through a designated barrel mechanism.
Explosion or Combustion: The force driving the projectile must come from an expanding gas explosion or chemical combustion (such as gunpowder).

The Frame or Receiver Rule

One of the most common legal traps involves broken or completely disassembled weapons. Under PC 16520(b), the law dictates that a firearm legally includes the frame or receiver of the weapon.

The frame or receiver is the core housing module that holds the mechanical firing components together. Because of this clause, you can be charged with illegal firearm possession even if the gun is missing its barrel, firing pin, slide, or ammunition.

Precursor Parts and "Ghost Guns"

California law aggressively monitors "ghost guns"—unserialized, home-manufactured weapons. Under recent legislative updates to PC 16520, the definition includes firearm precursor parts (unfinished frames or receivers) that can be readily converted into a functional housing unit.

What is NOT Legally a Firearm Under PC 16520?

Understanding what falls outside the scope of PC 16520 is often the key to defeating a weapons charge.

BB Guns and Pellet Guns: Since BB guns, airsoft guns, and pellet rifles use compressed air, $CO_2$, or mechanical springs instead of chemical combustion or gunpowder explosions, they are not considered firearms under this law. (Note: You may still be charged separately for brandishing or assaulting with a deadly weapon).
Unloaded Antique Firearms: Legally produced on or before 1898, or replicas using matchlock, flintlock, or percussion cap systems, are specifically exempt from several key provisions of PC 16520, as long as they are kept completely unloaded.

Why This Specific Definition Matters in Criminal Court

If you are facing a criminal charge in California involving a weapon, the prosecution must prove that the item involved satisfies the elements of PC 16520. If your defense attorney can show the item fails to meet this specific statutory definition, the primary gun charges can completely collapse.

PC 16520 forms the basis of proof for dozens of serious charges, including:

Felon in Possession of a Firearm (PC 29800): Prohibits convicted felons or those with certain misdemeanors from possessing items that fall under the PC 16520 definition.
Carrying a Concealed Firearm (PC 25400): Focuses on pistols, revolvers, or frames capable of being hidden on a person or within a vehicle.
Assault with a Firearm (PC 245(a)(2)): Elevates a simple assault to a severe felony carrying up to 4 years in state prison solely because of the presence of a statutory firearm.
Firearm Enhancements (e.g., PC 12022.5): Adds mandatory consecutive prison sentences if a legal firearm was used during the commission of another felony offense.

Frequently Asked Questions (FAQs)

Can I be charged with a firearm offense if the gun was completely inoperable?

Yes, in many cases. Because California law includes the frame or receiver alone in its core definition, a gun does not necessarily have to be functional or capable of firing at the moment of your arrest to expose you to illegal possession charges.

Is a flare gun considered a firearm under California law?

Generally, signaling devices designed purely for emergency or distress purposes are treated differently under specific transport codes.

However, PC 16520 explicitly notes that rocket-propelled launchers or similar devices containing explosive/incendiary material will be treated as firearms under major enforcement statutes like carrying loaded weapons in public.

Does a toy gun painted to look real fall under PC 16520?

No. A replica or toy gun lacks the internal combustion and barrel mechanics required by the statutory definition. While pointing a realistic replica at someone can still lead to severe charges like brandishing an imitation firearm (PC 417.4), it cannot trigger standard felony firearm charges.

Is an 80% lower receiver legally considered a firearm under this law?

Yes. Under updated California legislation integrated into PC 16520, unfinished frames or receivers—commonly called "80% lowers" or firearm precursor parts—are included in the definition.

Since these parts are designed to be easily finished, milled, or turned into the functional housing of a weapon, possessing them without following state serialization and registration laws is legally equivalent to owning a fully assembled firearm frame.

Does a muzzleloader or black powder rifle count as an antique exclusion?

It depends entirely on whether it is loaded. While an unloaded black powder or muzzleloading rifle manufactured before 1898 (or an exact replica using loose powder instead of fixed ammunition) is classified as an antique and is exempt from many possession and transfer restrictions, it loses this protected status the moment it is loaded. If it is loaded, or if it is used to commit a crime, it is treated fully as a statutory firearm.

Speak to a Skilled California Criminal Defense Lawyer

Because firearm definitions, restrictions, and precursor-part regulations in California change quickly, handling a weapons charge requires careful legal analysis.

Officers often mistakenly classify replica air-powered devices, antique items, or mechanical parts as illegal firearms, leading to wrongful arrests and excessive charges by overly aggressive prosecutors.

A qualified California criminal defense attorney at Eisner Gorin LLP will evaluate the physical evidence in your case.

By collaborating with forensic ballistics experts, asserting your Fourth Amendment rights against illegal searches, and holding the state strictly to the definition within Penal Code § 16520 PC, your legal team can fight to get your charges reduced or completely dismissed.

If you or a loved one is facing criminal allegations involving a firearm, do not leave your freedom to chance. Schedule your consultation by calling (818) 781-1570 or using the contact form.

Definition of a Firearm