Untraceable Firearms and Serialization Requirements:
Sections 121C and 121D

Chapter 135 of the Acts of 2024^[1] introduced Sections 121C^[2] and 121D^[3] to address the growing concern over untraceable firearms.

What Is an Untraceable Firearm?

Under the updated definitions in Section 121^[4], an "untraceable firearm," commonly known as a ghost gun, is any firearm, including a frame or receiver, that lacks a serial number assigned by a licensed manufacturer or importer, or that has had its serial number altered, removed, or obliterated. Because Section 121 defines "firearm" to include an unfinished frame or receiver, an unserialized frame or receiver, such as a so-called "80% lower" or a parts-kit or 3D-printed build, qualifies as an untraceable firearm and must be serialized. These items are reached through the "firearm" definition, not enumerated separately in the untraceable-firearm definition.

Section 121C: Serialization Requirements

Section 121C requires that all firearms possess a valid, legible serial number. Key provisions include:

• No person shall possess, sell, transfer, or manufacture a firearm that does not bear a serial number
• Persons who currently possess unserialized firearms must apply to have them serialized through an approved process
• It is unlawful to alter, remove, or obliterate the serial number on any firearm
• Frames and receivers, whether completed or unfinished beyond a certain threshold, are subject to serialization requirements

Section 121D: 3D Printers and CNC Machines

Section 121D regulates the use of additive manufacturing (3D printing) and computer numerical control (CNC) equipment to produce firearm components:

• Persons who use 3D printers or CNC machines to manufacture firearm frames, receivers, or other regulated components must register with the state
• Manufacturing a firearm component using these methods without proper licensing is prohibited
• Selling, offering to sell, or transferring a 3D printer or CNC milling machine whose primary or intended function is manufacturing or assembling firearms is prohibited (Section 121D(b))
• A violation of Section 121D is punishable by imprisonment for not more than 1 year or by a fine of not more than $5,000 per firearm per violation, or both (Section 121D(d))

Compliance for Existing Unserialized Firearms

Serialization under Section 121C does not apply to firearms manufactured before October 22, 1968, or to antique firearms, which Section 121 excludes from the definition of "firearm" altogether. Section 121C(g) also exempts firearms bound for destruction, in common-carrier transit, or lawfully carried through the state in the custody of a nonresident owner and stored per Sections 131C and 131L. Owners of home-built or other non-exempt unserialized firearms should consult current EOPSS guidance on the serialization process and compliance deadlines.

Penalties

Section 121C itself does not contain penalty provisions. Criminal penalties for untraceable firearm violations are found in MGL Chapter 269, Section 11C, which provides imprisonment of not less than 12 months and not more than 2.5 years for knowingly manufacturing, assembling, importing, selling, transferring, purchasing, or receiving an untraceable firearm. There is no fine-only option. Possession of an untraceable firearm is prima facie evidence of guilt under Section 11C, rebuttable by showing lack of knowledge. Additional charges may be brought under Chapter 269, Section 10 for unlawful possession.

See also: Untraceable Firearms (Ghost Guns) in Massachusetts: What the Law Says

See also: Building a Firearm from a Lower Receiver in Massachusetts