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

Chapter 135 added Sections 121C and 121D to address firearm serialization and specified uses or sales of 3D printers and CNC milling machines.^[1] The sections regulate different conduct and do not create a general registry for manufacturing equipment.

Which Items Are Firearms

Section 121 includes frames, receivers, and unfinished frames or receivers in the firearm definition.^[4] An unfinished item is covered when it may readily be completed to function as a frame or receiver or is marketed or sold to become one. A label such as "80 percent lower" is not the statutory test, and a raw piece of material is not automatically a firearm merely because it could be machined.

Section 121C: Serial Numbers

Section 121C generally requires firearms to bear a valid serial number and prohibits specified conduct involving firearms without one.^[2] A person manufacturing or assembling a privately made firearm must obtain a serial number before starting, place it on the firearm during manufacture or assembly, and register the completed firearm within seven days.

Guidance Letter #4 gives inconsistent transition dates for older unserialized firearms: Question 35 states October 28, 2026, while Question 8 states October 2, 2026.^[5] Current instructions should be confirmed with DCJIS.

Section 121D: Equipment Use and Sale

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

Penalties and Scope

Section 121C supplies the serialization requirements, while Chapter 269, Section 11C contains criminal penalties for specified untraceable-firearm conduct. Section 121D has its own penalties and exemptions. The classification of the item and the exact conduct determine which rule applies.