Threaded barrel laws in California turn on what kind of firearm the barrel is attached to. A threaded barrel on a semi-automatic pistol with a detachable magazine makes the pistol an assault weapon under Penal Code 30515, and the same is true for certain “other” semi-automatic centerfire firearms. On a rifle, a shotgun, or any manually operated firearm like a bolt-action or pump-action, a threaded barrel is legal on its own. The threads themselves are never the crime; the classification comes from the combination of action type, magazine configuration, and threaded barrel.
When a Threaded Barrel Makes a Firearm an Assault Weapon
Two firearm categories become assault weapons the moment a threaded barrel is present alongside a detachable magazine.
Semi-Automatic Pistols
Under Penal Code 30515(a)(4), a semi-automatic pistol that accepts a detachable magazine and has a threaded barrel capable of accepting a flash suppressor, forward handgrip, or silencer is an assault weapon.1California Legislative Information. California Penal Code 30515 Nothing has to be screwed onto the threads. The capability alone is enough.
The statute is not limited to centerfire pistols, which catches many owners of .22 LR target pistols off guard. Popular rimfire models often ship with threaded barrels from the factory, and those pistols fall under the same classification if they take a detachable magazine.
“Other” Semi-Automatic Centerfire Firearms
California also restricts threaded barrels on semi-automatic centerfire firearms that don’t qualify as a rifle, pistol, or shotgun. Under Penal Code 30515(a)(9)–(11), these firearms become assault weapons if they lack a fixed magazine and have a threaded barrel capable of accepting a flash suppressor, forward handgrip, or silencer.2State of California – Department of Justice – Office of the Attorney General. “OTHER” ASSAULT WEAPON INFORMATION This category covers certain AR-platform and AK-platform builds that fall outside traditional rifle or pistol definitions.
The Detachable Magazine Hinge
Both provisions require a detachable magazine. A semi-automatic pistol with a fixed magazine and a threaded barrel does not meet the assault weapon definition, because the statute requires both a detachable magazine and a listed feature to be present at the same time.
When a Threaded Barrel Is Legal
The assault weapon features list for rifles under Penal Code 30515(a)(1) includes pistol grips, thumbhole stocks, folding or telescoping stocks, grenade launchers, flash suppressors, and forward pistol grips. A threaded barrel is not on that list.3State of California – Department of Justice – Office of the Attorney General. Assault Weapons Laws (California and Federal Law) A semi-automatic centerfire rifle can legally have a threaded barrel without that feature alone or in combination with other features pushing it into assault weapon territory.
What you screw onto the threads still matters. A flash suppressor attached to that barrel is a restricted feature under (a)(1)(E). A thread protector or a muzzle brake that doesn’t qualify as a flash suppressor keeps the rifle legal, but threading on an actual flash suppressor while also having a detachable magazine would create an assault weapon.
Manually operated firearms sit outside the assault weapon framework entirely. Penal Code 30515 applies only to semi-automatic actions, so a bolt-action rifle, lever-action rifle, or pump-action shotgun with a threaded barrel is legal regardless of its other features.
Why the State Treats Threaded Barrels This Way
The concern is suppressors. A threaded barrel is the standard attachment point for one, and California bans suppressor possession outright. Under Penal Code 33410, possessing a silencer is a felony punishable by state prison time, a fine of up to $10,000, or both. No civilian exception exists. Federal law has loosened suppressor restrictions, and the $200 NFA tax stamp for suppressors was eliminated as of January 1, 2026, under the One Big Beautiful Bill Act, but California’s flat ban remains in effect.4ATF. Application to Transfer and Register NFA Firearm (Tax-Paid) Owning a threaded-barrel pistol and a suppressor in the same state stacks two separate felonies.
Criminal Penalties
Possession
Possessing a firearm that qualifies as an assault weapon because of a threaded barrel is charged under Penal Code 30605. The offense is a wobbler, meaning prosecutors can file it as a misdemeanor or a felony. A misdemeanor conviction carries up to one year in county jail. A felony conviction carries 16 months, two years, or three years in state prison.5California Legislative Information. California Penal Code 30605 A narrow exception exists for a first-time violation where the person lawfully owned the firearm before it was classified as an assault weapon, possessed no more than two such firearms, and relinquished them. That scenario can result in a fine of up to $500 instead of jail time.
Manufacturing, Importing, or Selling
Manufacturing, distributing, transporting into the state, or selling an assault weapon is a straight felony under Penal Code 30600. The sentence is four, six, or eight years in state prison.6Justia Law. California Penal Code 30600-30675 This statute frequently applies to people who modify firearms after purchase or bring pre-configured firearms in from other states. Adding a threaded barrel to a semi-automatic pistol at home and then selling or giving it away exposes you to these charges.
Stacked Charges
Assault weapon possession rarely gets charged alone. Carrying the firearm loaded in public under Penal Code 25850 is normally a misdemeanor, but it escalates to a felony when the firearm is an assault weapon.7California Legislative Information. California Penal Code 25850 Carrying it concealed without a permit under Penal Code 25400 follows the same pattern, with enhanced penalties for assault weapons.8California Legislative Information. California Penal Code 25400 One traffic stop can turn into several felony charges if the firearm in the vehicle qualifies as an assault weapon.
Bringing a Non-Compliant Firearm Into Compliance
If you own a semi-automatic pistol with a threaded barrel that would otherwise qualify as an assault weapon, three options remove the problem.
- Convert to a fixed magazine. The classification under 30515(a)(4) requires the pistol to accept a detachable magazine, so converting to a fixed magazine takes the firearm out of the definition and lets you keep the threaded barrel.1California Legislative Information. California Penal Code 30515
- Permanently attach a thread cap. If the barrel can no longer accept a suppressor or other device, the feature is gone. The ATF recognizes permanent attachment methods including full-fusion welding, high-temperature silver soldering at 1,100°F or above, and blind pinning with the pin head welded over. A gunsmith familiar with California compliance work can perform this for roughly $50 to $150.9ATF. Chapter 2 – What Are “Firearms” Under the NFA? (Permanent Attachment Methods)
- Swap the barrel. Replacing the threaded barrel with a non-threaded barrel of the same caliber is the cleanest fix when the pistol model supports it.
For “Other” semi-automatic centerfire firearms, the same logic applies: fix the magazine, or permanently address the threads.
Registration Is Closed
California has periodically opened registration windows for newly restricted firearms. The most significant were in 2000, when the original assault weapon definitions expanded, and in 2018, when owners of “bullet-button” assault weapons were required to register by June 30, 2018. A federal court in Sharp v. Becerra reopened registration for 90 days starting January 13, 2022, but only for people who had tried to register before the 2018 deadline and were blocked by technical problems with the state’s website.10State of California – Department of Justice – Office of the Attorney General. Bullet-Button Assault-Weapon Registration Information
No registration window is currently open. If your firearm became an assault weapon because of a threaded barrel and you did not register during one of those periods, there is no after-the-fact path to registration. The remaining options are the compliance modifications above, relinquishing the firearm, or transferring it out of state.
Seizure and Forfeiture
Law enforcement can seize firearms classified as assault weapons during investigations, traffic stops, compliance checks, or any lawful encounter. Under Penal Code 30800, an assault weapon deemed a public nuisance is subject to destruction so that it can no longer be used. The only exception is a court finding or a declaration from the Department of Justice, district attorney, or city attorney that preserving the weapon serves the interest of justice.11California Legislative Information. California Penal Code 30800 Upon conviction of any offense involving illegal possession or use of an assault weapon, the firearm is automatically deemed a public nuisance and destroyed.
Penal Code 18010 provides additional authority for confiscation and summary destruction of prohibited weapons found within the state.12California Legislative Information. California Penal Code 18010 The state does not provide a path for returning a prohibited assault weapon to its owner unless the owner can establish lawful possession under a recognized exemption. Given the range of penalties, from misdemeanor jail time to eight years in state prison, a criminal defense attorney experienced in California firearms cases is worth consulting before a compliance check rather than after one.
Passing Through California From Another State
If you legally own a firearm with a threaded barrel in another state and need to travel through California, the federal Firearm Owners’ Protection Act provides a safe-passage provision. Under 18 U.S.C. § 926A, you may transport a firearm through a state where it would otherwise be restricted, provided you can legally possess it at both your origin and destination, the firearm is unloaded, and neither the firearm nor ammunition is readily accessible from the passenger compartment. In a vehicle without a separate trunk, the firearm must be in a locked container other than the glove compartment or console.13Office of the Law Revision Counsel. 18 U.S. Code 926A – Interstate Transportation of Firearms
Safe passage protects transit only. Stopping in California for an extended stay, visiting a range, or conducting any business with the firearm removes the protection. California law enforcement has historically interpreted this provision narrowly, so every requirement has to be met.