Gun Parts Banned in Washington State: Bump Stocks and Magazines

Several categories of gun parts are banned in Washington State under RCW Chapter 9.41: machine gun conversion components and bump stocks are contraband, large-capacity magazines cannot be sold or manufactured, a long list of features turns a semi-automatic firearm into a prohibited assault weapon, and unserialized frames and receivers are restricted. Penalties run from a $500 civil fine for a first ghost gun offense up to a gross misdemeanor carrying a year in jail and a $5,000 fine.

Machine Gun Parts and Bump Stocks

RCW 9.41.220 declares machine guns, bump-fire stocks, undetectable firearms, short-barreled shotguns, and short-barreled rifles contraband when illegally possessed. The same statute reaches any part designed exclusively for use in one of these weapons or for converting a firearm into one.¹

That covers auto sears, drop-in auto sears, lightning links, and any similar component designed to make a semi-automatic firearm fire automatically. It also covers forced reset triggers and other rapid-fire devices that let a firearm fire without a separate trigger pull for each shot; Washington’s Attorney General moved in 2025 to block the return and sale of forced reset triggers, treating them as machine gun conversion devices.²

Bump stocks remain banned under Washington law even after the U.S. Supreme Court struck down the federal bump stock rule in 2024. Law enforcement has a duty to seize any of these items when found.¹

Large-Capacity Magazines

Since July 1, 2022, Washington has banned the manufacture, import, distribution, sale, and offer for sale of any ammunition feeding device holding more than 10 rounds. The prohibition also covers combinations of parts that can be assembled into such a magazine when one person controls all the parts.³

Personal possession of a magazine you already owned before July 1, 2022, is not the target. You can keep pre-ban magazines. What you cannot do is sell, distribute, or transfer them to another person inside Washington. The only legal way to offload one is through a licensed dealer facilitating a sale to a buyer outside the state.³

Licensed manufacturers and dealers may still sell large-capacity magazines to law enforcement, the U.S. armed forces, the Washington State military, and out-of-state buyers who can legally possess them. A violation is a gross misdemeanor: up to one year in county jail, a fine of up to $5,000, or both.³

Assault Weapon Features

HB 1240, signed April 25, 2023, makes it illegal to manufacture, import, distribute, sell, or offer for sale any assault weapon in Washington.⁴ The definitions in RCW 9.41.010 are feature-based, so an individual part can push an otherwise legal firearm into prohibited territory.

Rifles

A semi-automatic, center-fire rifle with a detachable magazine becomes an assault weapon if it has any one of these features:

A pistol grip that protrudes beneath the action and is independent of the stock (a fin attachment does not exempt a grip that still resembles a pistol grip)
A thumbhole stock
A folding or telescoping stock
A forward grip, whether vertical, angled, or pistol-style, designed for the non-firing hand
A flash suppressor, flash hider, sound suppressor, silencer, or any device designed to reduce the visual or audio signature
A muzzle brake or recoil compensator affixed to the barrel
A threaded barrel designed to accept a suppressor, flash hider, or similar attachment
A grenade or flare launcher
A barrel shroud (a heat shield encircling the barrel), except a solid forearm stock covering only the bottom

Muzzle brakes and compensators are standard on many sporting rifles, and they still count as prohibited features when paired with a detachable magazine on a semi-automatic center-fire platform.⁵

Pistols and Shotguns

For a semi-automatic pistol with a detachable magazine, the prohibited features are a threaded barrel, a second handgrip, a barrel shroud, or the ability to accept a magazine outside the pistol grip.⁵

For a semi-automatic shotgun: a folding or telescoping stock, a pistol grip, a thumbhole stock, a forward grip, a fixed magazine holding more than seven rounds, or a revolving cylinder.⁵

Combinations of Parts

The definition of “assault weapon” also includes combinations of parts from which an assault weapon can be assembled, or a firearm converted into one, when the parts are controlled by the same person. A collection of components that together create a banned configuration counts as possessing an assault weapon, even if nothing is currently assembled.⁵

If You Already Owned One

Assault weapons and qualifying components owned before April 25, 2023 can be kept. Inheritance from a deceased owner who legally possessed the weapon is also allowed. But the transfer options are narrow: sale or gift to a licensed dealer, delivery to a gunsmith for service, or surrender to law enforcement. You cannot sell an assault weapon to another Washington resident, though licensed dealers may facilitate transfers to out-of-state buyers. A violation is a gross misdemeanor.⁴

Unserialized Frames and Receivers

RCW 9.41.326 bans the manufacture, sale, transfer, purchase, and knowing possession of untraceable firearms, meaning guns without a serial number from a licensed manufacturer, importer, or dealer. The prohibition extends to unfinished frames and receivers (often called “80% lowers”) that can be readily completed into functional firearms. Antique firearms, firearms made before 1968, and firearms rendered permanently inoperable are excepted.

Penalties escalate with each offense:

First violation: civil infraction, fine up to $500
Second violation: misdemeanor, up to 90 days in jail and a fine up to $1,000
Third or later violation: gross misdemeanor, up to one year in jail and a fine up to $5,000

A first offense is not a criminal conviction, but a second one is. Unfinished frames and receivers are also subject to background check requirements when transferred.

Short-Barreled Rifle and Shotgun Parts

Rifles with barrels under 16 inches and shotguns with barrels under 18 inches are tightly restricted under both federal and Washington law. RCW 9.41.220 makes these weapons, and any parts designed exclusively for building or converting a firearm into one, contraband when illegally possessed.¹

Federal law layers on top: short-barreled weapons require registration under the National Firearms Act and a $200 tax. Possessing a short barrel next to a compatible receiver without proper NFA registration can trigger both state and federal violations.

Parts Often Assumed Banned but Legal

Not every part that sounds restricted is prohibited on its own. Standalone suppressors are legal to own in Washington with proper federal NFA registration. Attaching one to a semi-automatic rifle with a detachable magazine, though, turns that rifle into an assault weapon under state law.⁵ The part is not banned; the combination is.

Standard-capacity magazines holding 10 rounds or fewer are unrestricted. Replacement springs, barrels, triggers, and other internal components that do not change a firearm’s legal classification are legal. Stripped lower receivers carrying a serial number are treated as firearms for transfer and background check purposes but are not themselves prohibited.

The line running through Washington’s firearms law is the difference between a part in isolation and a part in context. A threaded barrel in a parts bin is a barrel. Installed on a semi-automatic pistol with a detachable magazine, it creates an assault weapon. What your parts become when combined is where compliance actually lives.

1
Washington State Legislature. Washington Code RCW 9.41.220 – Unlawful Firearms and Parts Contraband
2
Washington Attorney General. AG Brown Blocks Returns and Sales of Machine-Gun Conversion Devices in Washington
3
Washington State Legislature. Washington Code RCW 9.41.370 – Large Capacity Magazines
4
Washington State Legislature. Washington Code RCW 9.41.390 – Assault Weapons
5
Washington State Legislature. Washington Code RCW 9.41.010 – Definitions