Possession of a "Bump Stock" in California
(Penal Code 32900)


Bump stocks” -- also known as “multiburst trigger activators” -- are gun accessories that increase the rate at which semiautomatic rifles fire.1Bump stocks are illegal in California under Penal Code 32900.

Penalties for Possession of a Bump Stock in California

Possessing, manufacturing or lending someone a bump stock is a “wobbler” offense in California. It can be prosecuted as a misdemeanor or a felony in the prosecutor's discretion.

As a misdemeanor, the penalty for possession of a bump stock is up to one year in county jail.

Felony possession of a bump stock in California can be punished by 18 months to three years in jail.

Legal Defenses

Legal defenses to Penal Code 32900 charges include:

  • The defendant was legally permitted to own the bump stock.
  • The defendant was taking the bump to law enforcement for destruction.
  • The defendant did not know the bump stock was in his/her possession.
  • The bump stock belonged to someone else.
  • The bump stock was found during an illegal search.
  • There was police misconduct, such as a coerced confession or planted evidence.

To help you better understand California's law on illegal bump stocks and other firearms modifications, our California criminal defense lawyers discuss, below:

1. What are “bump stocks”?

California Penal Code 16930 defines “bump stocks” -- legally known as “multiburst trigger activators” – as either of the following:

  • A device designed or redesigned to be attached to a semiautomatic firearm, which allows the firearm to discharge two or more shots in a burst by activating the device; or
  • A manual or power-driven trigger activating device constructed and designed so that when attached to a semiautomatic firearm it increases the rate of fire of that firearm.

In plain English, a bump stock is a type of firearm modification. It is an accessory that modifies a semiautomatic rifle so that it can fire shots continuously as long the shooter keeps the rifle against his or her shoulder.

The bump stock -- also referred to as a "reciprocating stock" -- takes the place of the gun's “standard stock” (that is, the piece of a semiautomatic rifle that rests against the shooter's shoulder).

By holding down the trigger and placing pressure on the barrel of the gun, a shooter using a bump stock can shoot almost as quickly as an automatic firearm.

Bump stocks were used during the Las Vegas mass shooting on October 1, 2017, which resulted in the death of 58 victims. As a result of using bump stocks, the shooter was able to fire approximately 90 in just 10 seconds.

2. Do reciprocating stocks convert guns into automatic weapons?

Technically, no. Bump stocks do not convert semi-automatic guns to automatic ones, even though they allow semiautomatic rifles to be fired almost as automatically.

3. Aren't multi-burst trigger activators legal under federal law?

Federal law does not prohibit possession of a bump stock. Federal law prohibits possession of any "machine gun" (that is, a fully automatic weapon) manufactured after May 19, 1986. Under federal law, a "machine gun" is defined as:

"any weapon which shoots, is designed to shoot, or can be readily restored to shoot, automatically more than one shot, without manual reloading, by a single function of the trigger."2

This definition does not apply to a semiautomatic rifle with a bump stock. So for the present, at least, possession of a bump stock is not illegal under federal law.

 4. Are bump stocks legal in California?

California Penal Code 32900 makes it illegal to possess, manufacture, import or sell a bump stock in California. Bump stocks have been illegal in California since 1990.3

Specifically, California Penal Code 32900 provides:

"Except as provided in Chapter 1 (commencing with Section 17700) of Division 2 of Title 2, any person in this state who manufactures or causes to be manufactured, imports into the state, keeps for sale, or offers or exposes for sale, or who gives, lends, or possesses any multiburst trigger activator is punishable by imprisonment in a county jail not exceeding one year or imprisonment pursuant to subdivision (h) of Section 1170."

5. Who may legally own a multiburst trigger activator?

People who may legally possess a bump stock in California include:

  • Historical societies and museums;
  • Authorized participants in a movie, television show, or video production;
  • People who sell or rent bump stocks to museums or entertainment productions; and
  • Law enforcement personnel.4

Such use is subject to obtaining permission, where applicable, and to such possession being otherwise in compliance with applicable law.

6. What is the penalty for possessing a bump stock in California?

Possession of a bump stock is a California “wobbler” offense. That means it can be prosecuted as either a California misdemeanor or a California felony, in the prosecutor's discretion.

If prosecuted as a misdemeanor, possession of a bump stock can be punished by up to one (1) year in county jail.

As a felony, possessing a bump stock can result in a jail sentence of:

  • 18 months, 
  • Two (2) years, or
  • Three (3) years.5

For further information, please see our article on Felony Sentencing in California.

Note additionally, that regardless of whether the offense is prosecuted as a misdemeanor or a felony, a multiburst trigger activator can be confiscated as a nuisance by the California Attorney General.6

7. What are some legal defenses to California Penal Code 32900 charges?

The best defense to charges of modifying a firearm with an illegal bump stock will depend on the specific facts of the case.

The following, however, are some of the most common defenses to bump stock charges under Penal Code 32990:

  • The defendant was legally permitted to own the bump stock.
  • The defendant was taking the bump stock to law enforcement for the authorities to dispose of.7
  • The defendant did not know the bump stock was in his/her possession.
  • The bump stock belonged to someone else.
  • The bump stock was found during an illegal search and seizure.
  • There was police misconduct, such as a coerced confession or planted evidence.

Charged with a gun crime in California? Call us for help…

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If you have been charged with possession of a bump stock or another California gun crime, we invite you to contact us for a free consultation.

Our California gun crimes attorneys represent clients throughout the state on firearms offenses and related charges.

Call us at 855-LAWFIRM or complete the form on this page to speak to a lawyer confidentially about your case.


Legal references:

  1. California Penal Code 16930 PC,
  2. The term also includes the frame or receiver of any such weapon, any part designed and intended solely and exclusively, or combination of parts designed and intended, for use in converting a weapon into a machinegun, and any combination of parts from which a machinegun can be assembled if such parts are in the possession or under the control of a person. 26 U.S. Code 5845. See also Section (o) of 18 U.S. Code 922 (unlawful acts involving firearms).
  3. See press release regarding California Department of Justice bump stock advisory, October 19, 2017.
  4. See Penal Code 17700 and subsequent sections.
  5. Penal Code 32900; Penal Code 1170(h).
  6. Penal Code 32990. See also Penal Code 18010.
  7. See Penal Code 17735.

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