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

Massachusetts regulates untraceable firearms, privately made firearms, unfinished frames and receivers, and certain firearm-manufacturing activity through separate provisions. The rules should not be collapsed into a claim that every unfinished object is a firearm or that every 3D-printer owner must register equipment.

What Counts as an Untraceable Firearm

Section 121 defines an untraceable firearm as a firearm that lacks a serial number or other identification required by law, or whose identification has been removed, defaced, altered, obliterated, or mutilated.^[1] A frame, receiver, or unfinished frame or receiver can be a firearm under the same section. For unfinished items, the statutory readiness and marketing tests matter; a percentage label does not control.

Serialization and Registration

Section 121C generally bars possession, sale, transfer, manufacture, or assembly of a firearm without a valid serial number.^[2] A person making a privately made firearm must obtain a serial number before manufacture or assembly, place it on the firearm during the process, and register the completed firearm within seven days. Registration is handled through the MIRCS Unified Gun Portal.^[6]

Guidance Letter #4 contains inconsistent transition dates for previously unserialized firearms: Question 35 states October 28, 2026 for compliance with Sections 121B and 121C, while Question 8 states October 2, 2026 for serialization.^[5] Owners should not wait and should confirm the current deadline with DCJIS.

3D Printers and CNC Milling Machines

Section 121D requires a valid LTC to use a 3D printer or CNC milling machine to manufacture or assemble a firearm.^[3] It also restricts sale or transfer of machines advertised, marketed, or promoted primarily for firearm manufacture. The section does not require owners or users of general-purpose equipment to register the machine with the state.

Penalties

Section 121C states the serialization rules. Criminal penalties for specified untraceable-firearm conduct are in Chapter 269, Section 11C.^[10] Section 121D contains separate penalties for prohibited equipment use or transfer. Which provision applies depends on the conduct and item involved.

Current Federal Rule

The Supreme Court held in Bondi v. VanDerStok that ATF had statutory authority to regulate at least some weapon-parts kits and unfinished frames or receivers.^[7] Current 27 C.F.R. Section 478.12 remains in effect and applies to certain readily completable items, while its text excludes some raw or unindexed blanks depending on their condition and circumstances.^[8] ATF's May 2026 legal review could lead to a future proposal, but the review itself did not repeal the current rule.^[9]

Practical Compliance

• Use the statutory tests, not an "80 percent" marketing label.
• Obtain the required serial number before making a privately made firearm.
• Register the completed firearm within the statutory period.
• Do not assume federal compliance establishes Massachusetts compliance.