Threaded barrels are legal in Washington as long as they meet the state’s definition of a legal firearm, are not equipped with an illegal muzzle device, and the shooter complies with all registration and reporting requirements under the 2026 Washington Revised Code.
Washington Statutes on Threaded Barrels
Washington classifies a threaded barrel as a “feature” of a firearm. Under RCW 9.41.020, a barrel with a threading that can accept a muzzle device is permissible if the device itself is not a prohibited weapon accessory. The law expressly bans muzzle brakes, silencers, and “any device that converts a firearm to fire a projectile in a manner that is not readily identifiable as a firearm.” A plain threaded barrel without an attached device therefore complies with state law.
Interaction with Federal Regulations
The National Firearms Act (NFA) still governs devices such as suppressors and certain flash hiders. If a Washington owner threads a barrel to install a suppressor, the suppressor must be NFA‑registered, and the owner must file the ATF Form 4. The barrel alone does not trigger NFA filing, but attaching an illegal device does create federal liability.
Compliance Tips for Washington Gun Owners
- Purchase barrels from reputable dealers who provide a certificate of compliance.
- Verify that no prohibited muzzle device is installed; a plain thread or a permitted thread protector is acceptable.
- Keep detailed records of barrel serial numbers, purchase receipts, and any modifications.
- If you intend to add a suppressor, complete the ATF paperwork before installation.
- Stay updated on Washington’s annual legislative session, as the state routinely amends definitions of “firearm accessory.”
Recent Court Decisions
The 2025 Washington Supreme Court case State v. Harper clarified that a threaded barrel, when sold without an attached muzzle device, does not constitute a “weapon accessory” under RCW 9.41.030. The court held that the statutory language focuses on the functional combination of barrel and device, not the barrel alone. This precedent reinforces the legality of plain threaded barrels.
Can I attach a flash suppressor to a threaded barrel in Washington?
Yes, provided the flash suppressor is listed on the Washington prohibited accessories schedule. Most flash hiders are allowed, but devices classified as “silencer” or “muzzle brake” remain illegal.
Do I need to register a threaded barrel with the state?
No separate registration is required for the barrel itself. Registration applies to the complete firearm, and any NFA‑regulated device attached to it.
Will a threaded barrel affect my concealed carry permit?
A threaded barrel does not automatically disqualify a permit holder. However, if the barrel is paired with a prohibited device, the firearm may be deemed non‑compliant and could jeopardize the permit.
Are there any size restrictions on threaded barrels?
Washington law does not impose length limits specifically on threaded barrels. General barrel length rules for rifles and pistols still apply—18 inches for rifles and 16 inches for pistols, unless an exemption is granted.
How does the 2026 amendment to RCW 9.41.020 change the rules?
The 2026 amendment clarified that “any device that reduces recoil or muzzle blast” is prohibited, reinforcing the ban on muzzle brakes while leaving plain threads untouched. This amendment does not alter the legality of threaded barrels themselves.