Serial numbers on a home-built frame: when, where and how deep

Federal law does not require you to engrave a frame you build for your own use, but several states do, and doing it well protects you if the gun is ever sold, lost or inspected. This is the practical side; check your state for whether it is required.

What to engrave

The federal marking standard for licensees is a useful template: a unique serial number, and where required the maker name, city and state. Some states specify the format. Pick a number you can document, such as your initials and a date code, and keep a record.

Where

On the frame, in metal where possible. On a Polymer80 frame the accepted location is the front locking block rail insert or a dedicated metal serial plate, because polymer alone does not meet the depth standard in most rules. Some builders engrave the rear rail module instead.

How deep

The common standard is 0.003 inch minimum depth and 1/16 inch minimum character height. A rotary engraver or a laser engraver at a trophy shop will meet it; a hand-held electric scribe usually will not.

When

Before the frame is completed if your state requires it, and before the first range trip regardless. Some states set a deadline counted from completion or purchase.

Record it

Photograph the engraving, note the date, and keep it with the receipt. If you ever transfer the firearm through a dealer, that record is what they will ask for.