Washington 80% Lower Laws u2014 HB 1240 Impact on P80 Builds

For Washington residents interested in firearm building, the legal landscape changed fundamentally with the passage of House Bill 1240 in April 2023. This comprehensive guide details how Washington state law, specifically the “assault weapons” ban under HB 1240, interacts with federal regulations to govern the acquisition, possession, and building of firearms using Polymer80 frames and other 80% lower receivers. This is an analysis of published statutesu2014RCW 9.41.010 and RCW 9.41.390u2014and is not legal advice. All builders must verify current law and consult an attorney for specific guidance.

Understanding HB 1240: The 2023 Washington “Assault Weapons” Ban

Effective April 25, 2023, HB 1240 made the manufacture, import, distribution, sale, or offer for sale of so-called “assault weapons” a gross misdemeanor in Washington state. Critically for builders, the law’s definition of “manufacture” includes assembling a firearm from a frame or receiver. This directly impacts the construction of firearms from 80% lower frames, often called “P80 builds.” The ban applies to specific firearm categories listed in the statute, including many semi-automatic rifles and pistols with common features. It is essential to understand that possession of weapons legally owned before April 25, 2023, is generally grandfathered, but the pathways for creating new ones are now severely restricted.

Key Definitions: Frame, Receiver, and “Assault Weapon” Under RCW 9.41

Washington law incorporates and expands upon federal definitions. Under RCW 9.41.010:

• “Frame” or “receiver”: Defined similarly to federal law, it is the part of a firearm that provides housing for the hammer, bolt or breechblock, and firing mechanism.
• “Assault weapon”: HB 1240 adds a detailed definition in RCW 9.41.010(2). For builders, the most relevant categories include:
  • Semi-automatic rifles with a detachable magazine and one or more listed features (e.g., pistol grip, folding stock, flash suppressor).
  • Semi-automatic pistols with a detachable magazine and one or more listed features (e.g., threaded barrel, second handgrip, capacity to accept a magazine outside the pistol grip).
  • Specifically named firearm models and their copies.
• “Manufacture”: As noted, includes assembling from a frame or receiver, making the act of building a firearm that meets the “assault weapon” criteria potentially illegal after the ban date.

What You CAN and CANNOT Do Under Current Washington Law

This section outlines general compliance boundaries. Always confirm the status of specific components and configurations.

What You CAN Do (If compliant with all laws)

• Possess a firearm built from an 80% lower that was completed and possessed prior to April 25, 2023, provided it was legally owned.
• Build a firearm from an 80% lower that, when completed, does NOT meet the state’s definition of an “assault weapon” (e.g., a bolt-action, pump-action, or manually-operated firearm).
• Build a pistol-frame-based firearm that is featureless and compliant (e.g., a pistol without a threaded barrel, not capable of accepting a magazine outside the grip, etc.).
• Utilize a Washington FFL to serialize and transfer a frame/receiver in compliance with both state law and the federal ATF Final Rule 2021R-05F.
• Possess and use tools for legal firearm building and maintenance.

What You CANNOT Do

• Acquire (purchase, trade for, receive) an 80% frame/receiver after April 25, 2023 with the intent to build a firearm that would be classified as an “assault weapon” under HB 1240.
• Manufacture (assemble) a firearm from any frame/receiver after April 25, 2023, that meets the “assault weapon” criteria, regardless of when the frame was acquired.
• Distribute, sell, or offer for sale an “assault weapon,” including those built from 80% lowers.
• Ignore the federal requirement that personally made firearms (PMFs) without a serial number must be serialized by an FFL if later transferred. This is required under ATF Rule 2021R-05F.
• Build any firearm if you are prohibited from possessing firearms under state or federal law.

The Intersection of Washington HB 1240 and Federal ATF Rule 2021R-05F

Builders must navigate two overlapping regulatory schemes. While HB 1240 restricts *what* can be built, the federal ATF rule governs *how* unfinished frames and receivers are defined and transferred. As of August 2022, the ATF rule redefined many 80% products as “firearms” subject to serialization and transfer through an FFL with a background check. For Washington residents, this creates a potential compliance pathway: an unfinished frame can be transferred through an FFL, serialized, and logged into the FFL’s book. However, this does not override HB 1240’s prohibitions. An FFL cannot legally transfer a frame/receiver to a Washington resident if the intent or likely outcome is the manufacture of a banned “assault weapon.” This makes the choice of platform and final configuration paramount. For more on federal rules, see our federal law guide.

Serialization and FFL Transfer Pathway for Compliance

If you wish to legally begin a new build after April 2023 with a frame that falls under the ATF’s definition, you must typically do so via an FFL. The process involves:

1. Selecting a frame/receiver that, when built into a complete firearm, will not violate HB 1240.
2. Having a Washington FFL receive the frame (it is now considered a “firearm” per the ATF).
3. The FFL will serialize the frame per federal requirements before completing the transfer.
4. You will undergo the same background check process as purchasing a complete firearm (including any state-mandated waiting periods).
5. Upon successful transfer, you may take possession and complete the build, ensuring the final product remains feature-compliant with state law.

This pathway underscores the importance of pre-planning your build for state compliance. Not all FFLs are willing to handle these transfers, so contact them in advance.

Polymer80 Frame Models and Washington Legal Status Matrix

The following table outlines the general legal status for common Polymer80 frame models under Washington HB 1240, assuming intent to build a semi-automatic firearm. This is a general guide; final configuration determines legality. “Pre-Ban Grandfathered” refers to builds fully completed and possessed before April 25, 2023.

Common Misunderstandings About the Washington Ban

Clarifying frequent points of confusion is critical for compliance.

• Myth: “If I bought the 80% lower before the ban, I can build it anytime.” Reality: HB 1240 prohibits the *manufacture* (assembly) of an “assault weapon” after April 25, 2023. The date of assembly is key, not just the date of acquisition for the part.
• Myth: “The federal ATF rule makes 80% lowers illegal.” Reality: The ATF rule reclassifies them as firearms requiring serialization via an FFL for transfer, but does not ban them outright. State law (HB 1240) imposes separate restrictions.
• Myth: “Pistol builds are all okay.” Reality: Many semi-automatic pistol configurations are explicitly defined as “assault weapons” under the law. A Polymer80 pistol with a threaded barrel, for example, is likely banned from new manufacture.
• Myth: “I can serialize it myself to comply.” Reality: For personal use and no transfer, you may federally serialize a PMF. However, Washington’s HB 1240 restriction on *manufacture* is separate from serialization requirements.

Frequently Asked Questions (FAQ)