How To Recover a Firearm’s Serial Number?

What is Firearm’s Serial Number?

Serial numbers are issued to firearms for identifying purposes. When a gun is bought, the buyer registers it with the appropriate authorities, who enter the owner’s name and serial number into a database. Serial numbers are stamped into the metal frame of a weapon using extremely powerful dies that drive the numerals deep into the steel. If necessary, law enforcement may then track the number back to the original owner, or the owner to the gun.

Techniques Commonly used to Obliterates Numbers from Firearm’s

  • Scratching with Sharp Tool or Filing
  • Grinding with Power Tool
  • Peening with Hammer
  • Overstamping and Overpunching
  • Welding and Other Heating Processes
  • Rusting
  • Reapplication of the Original Finish

Firearm’s Serial Number Restoration

Firearms examiners are frequently presented with firearms that have illegible serial numbers. Criminals delete serial numbers in order to be “untraceable.” Many culprits are unaware that even if they erase a serial unique code number, the unique code number may remain visible. Physical and chemical procedures can be used by forensic scientists to restore or enhance damaged characteristics. Restoring a serial number can help police authorities with information on a firearm or other equipment, as well as providing a lead in an investigation.

To clear metal chips from the surface, scientists usually polish the metal with a sandpaper-like substance. They’ll subsequently etch the metal using chemical reagents, usually acids, until the number is recovered. Based on the different types of metal surfaces, the scientist will choose the appropriate chemical. Etching aluminium, zinc, and steel alloys, for example, requires various chemicals.

To restore the serial number Ballistics Expert should follow the steps below:

1. The ballistics expert determines the firearm’s make and model.

2. The ballistics expert looks up the manufacturer’s information to find the serial number’s location.

3. The ballistics expert disassembles the firearm and locates the serial numbers after ensuring that it is unloaded and safe.

4. The ballistics expert examines the damaged numbers to determine how they were damaged.

5. If a punch or drill was used, a low-powered stereo microscope may reveal many of the original numbers. More information may be revealed by polishing the surface with wet and dry abrasive paper.

6. The ballistics expert may decide to use a chemical agent to improve the serial number. The agent employed is determined by the weapon’s metal and is used to etch into the softer portions of the metal, disclosing the serial numbers.

7. In accordance with agency standards, the ballistics expert documents all steps with detailed notes and photographs.

Also Read: Serial Number Restoration From Metal Surfaces

Serial Number Restoration Methods

Magnaflux Method

This approach is beneficial since it is non-destructive and has no effect on the weapon. The firearm is initially magnetised by the forensic scientist. Magnetizing causes magnetic forces to ripple, which may be utilised to detect where the metal has become disordered as a result of the pressure stamping process. He next sprays some oil on the rifle to keep any iron-like particles suspended. These particles tend to collect in areas of the metal that are disorganised. This displays the concealed serial number’s position.

Chemical and Electrochemical Etching Method

An etching solution is painted over the area in concern by the forensic firearm examiner. The solution etches the disturbed metal faster than the surrounding metal. The figures are readily visible. The process can be sped up by using an electrical current (electrochemical etching). This procedure is inconvenient since it alters the physical characteristics of the evidence.

The etchants mentioned below are arranged in order of strength. Starting with a lesser etchant and progressing to stronger etchants as needed is the preferable method.

Fry’s Reagent (Solution B)

The Solution B process is a chemical etching procedure for restoring serial numbers in steel when used in conjunction with the polishing procedure.

Modified Fry’s Reagent (Solution G)

The Solution G process is a chemical etching procedure for restoring serial numbers in steel when used in conjunction with the polishing procedure.

Cupric Ammonium Chloride Solution (Heyn’s Reagent)

In stainless steel or cast iron, this process, when combined with the polishing procedure, is a successful approach to recover an obliterated serial number. To speed up the etching process, this solution can be used in combination with a rectifier.

Solution E (Ferric Chloride)

The Solution E (Ferric Chloride) process is a chemical etching procedure for restoring serial numbers in hard cast aluminium, mild steel, or brass when used in conjunction with the polishing procedure.

25% Nitric Acid

This is a chemical etching process for restoring serial numbers in steel, aluminium, and its alloys when used in conjunction with the polishing procedure.

Solution C (Dilute Nitric Acid)

The Solution C (Dilute Nitric Acid) process is a chemical etching procedure for restoring serial numbers in aluminium and pot metal when used in conjunction with the polishing procedure.

Ultrasonic Cavitation Method

The forensic scientist immerses the firearm in a special ultrasonic bath and inundates it with extremely high frequency vibrations in this approach. The cavitation is caused by these vibrations. Cavitation is the process of producing small bubbles along the metal’s surface. The process of cavitation begins to eat away at the metal after repeated exposure. Cavitation will eat away at the metal in areas where it is disorganised, revealing the serial number. This approach is a destructive one, similar to chemical etching.



  • Brandt, D., Metallurgy Fundamentals, Goodheart-Wilcox Co., Inc., 1992.
  • Doane, F.B., Principles of Magnaflux Inspection, Photopress Publishing, Inc., 1940.
  • Hatcher, J.S., Jury, F.J., and Weller, J., Firearms Investigation, Identification and Evidence, 2nd edition,
    Stackpole Books, Harrisburg PA, 1977.
  • Hein, Morris, et al., Foundations of College Chemistry, Dickenson Publishing Co., 1977.
  • Kegser, C.A., Basic Engineering Metallurgy – Theories, Principles and Applications, 6th edition, Prentice
    Hall, Inc., Englewood Cliffs, N.J. 1957.
  • Kehl, G.L., The Principles of Metallographic Laboratory Practice, 3rd edition, McGraw-Hill, New York,
  • Kotz and Purcell, Chemistry and Chemical Reactivity, Saunders College Publishing, 1991.
  • Krcma, V., The Identification and Registration of Firearms, Charles C. Thomas, Springfield, IL, 1971.
  • Matthews, J.H., Firearms Identification, Volume I, Charles C. Thomas, Springfield, IL, 1962 pp.77-80.
  • Polk, D.E., and Giessen, B.C., Metallurgical Aspects of Serial Number Recovery, Institute of Chemical
    Analysis-Northeastern University, Boston MA (undated).
  • Treptow, R.S., Handbook of Methods for the Restoration of Obliterated Serial Numbers, NASA, 1978.
  • Vander Voort, G.F., Metallography. Principles and Practice, McGraw-Hill, 1984.
  • Van Vlock, L.H., Elements of Materials Science and Engineering, Addision-Wesley Publishing Company,