Below is a comprehensive, legally compliant step-by-step guide to engraving serial numbers on firearms, based on ATF regulations and industry best practices. Always consult the ATF (Bureau of Alcohol, Tobacco, Firearms and Explosives) or legal counsel before proceeding.

⚠️ ​​Critical Legal Requirements​​

1. ​​Altering existing serial numbers is illegal​​ under federal law (National Firearms Act/Gun Control Act), punishable by fines up to $250,000 and/or 5 years imprisonment.
2. ​​Only applicable to​​:
   • ​​Privately Made Firearms (PMFs)​​: When manufacturing a firearm for personal use (not for sale), federal law does not require serialization. However, ​​if transferred or sold​​, engraving a unique serial number becomes mandatory.
   • ​​FFL-holders​​: Licensed manufacturers must serialize all firearms.
3. ​​Serial Number Standards​​:
   • Depth: ​​≥0.003 inches​​ (permanent engraving).
   • Height: ​​≥1/16 inch​​ characters.
   • Location: ​​Frame/receiver​​ (visible without disassembly).
   • Format: Unique alphanumeric sequence not duplicating other firearms.

🔧 ​​Step-by-Step Engraving Guide​​

​​1. Verify Legality & Purpose​​

• ​​Homemade firearms​​: Confirm state laws (e.g., California requires serialization even for personal-use PMFs).
• ​​Commercial gunsmiths​​: Hold an FFL license; engraving must occur before transfer .
• ​​Never engrave over existing serial numbers​​, damaged or not—contact ATF for guidance .

​​2. Equipment & Setup​​

• ​​Laser engraver​​: Use a ​​fiber laser​​ (e.g., Triumph 30W/50W) for deep, precise marks on metal .
  • Rotary attachment: Essential for cylindrical surfaces (barrels, magazines).
• ​​Workspace​​: Ventilated, fireproof, and compliant with ​​Class 4 laser safety standards​​ (enclosed, protective eyewear).
• ​​Software​​: LightBurn or EZcad for vector-based serialization templates.

​​3. Firearm Preparation​​

• ​​Disassemble​​: Remove non-engravable parts (springs, optics).
• ​​Clean surface​​: Degrease metal with alcohol to prevent uneven marks.
• ​​Secure firearm​​: Use vise clamps or a rotary jig to prevent movement.

​​4. Engraving Parameters​​

• ​​Test first​​: Use scrap metal to calibrate depth/legibility.
• ​​Depth verification​​: Use a digital depth gauge (≥0.003").

​​5. Engraving Execution​​

• ​​Placement​​: Engrave on the frame/receiver in a visible area (ATF standard) .
• ​​Process​​:
  1. Load serial number template into software.
  2. Align laser focal point perpendicular to the surface.
  3. Run engraving cycle; inspect after each pass.
• ​​Inspect​​: Ensure characters are clear, unbordered, and meet size/depth requirements.

​​6. Post-Engraving Compliance​​

• ​​Recordkeeping​​: Log the serial number, firearm details, and engraving date in a bound book (FFL requirement).
• ​​ATF notification​​: For PMFs intended for sale, submit ATF Form 2 (Manufacturer Registration).

⚠️ ​​Prohibited Actions​​

• ❌ ​​Relocating existing serial numbers​​.
• ❌ ​​Engraving over damaged numbers​​ (report to ATF instead).
• ❌ ​​Using non-compliant fonts/sizes​​ (e.g., cursive, <1/16").

💡 ​​Best Practices​​

• ​​Documentation​​: Photograph the engraved serial number and retain records indefinitely.
• ​​State laws​​: Some states (e.g., New York) require state-assigned serial numbers for PMFs.
• ​​Professional services​​: For non-experts, use ATF-compliant engravers like AAC Enterprises .

​​Disclaimer​​: This guide is informational. Compliance with federal, state, and local laws is the firearm owner’s responsibility. Penalties for violations are severe .