Serial Number Restoration on Firearms

Obliterated Serial Number on Gun Frame

In the United States, firearms manufactured after 1968 must contain a unique serial number somewhere on the metal frame. This number is contained on Firearms Transaction Record, or form 4473, at the time of purchase from a federal firearms license holder like a retail gun store. This form contains the pertinent information of the buyer of that firearm and can be used to trace that firearm back to the original owner. This is especially helpful when the weapon has been stolen.

There are a couple of different ways that manufacturers create this unique serial number but for the purposes of this posting I’ll keep it simple. The vast majority of modern firearms have their serial numbers stamped into the metal. Basically a very powerful press fitted with the alpha-numeric blocks strikes the metal in the same manner you might use an office ink stamp on paper. The process compresses the metal with tremendous force and alters the metallurgy even under the numbers themselves. This is a key aspect of why serial number restoration works.

Criminals using stolen weapons sometimes make efforts to deface or destroy that serial number (which is a crime) so police can not trace it back to the original owner. The gun may be from a relative, friend, or may link them to another crime such as burglary. There are a variety of ways a criminal might deface a serial number including grinding, drilling, hammering, and punching.  These efforts may make the numbers unidentifiable to the naked eye and criminals usually stop when they can not make out the numbers (just as they may stop cleaning when they stop seeing blood).

There are a variety of reagents and etching techniques dependent on the type of metal being worked on but for the sake of this article I’ll describe the use of Fry’s reagent (a chemical etchant). Step one in the process (after initial photography) is to polish down the metal (in the damaged area) to a smooth surface. During this process, or at anytime throughout the etching process, some numbers or letters may become visible. In fact, the analyst may never recover all of the numbers at the same time so documenting them along the way is crucial.

A cotton swab is used to apply the etchant, rubbing in the same direction. After a few minutes the area is cleaned with water, dried, and re-polished. The process is repeated, each time checking for any numbers that may have developed. Eventually, the analyst may develop the entire number (or enough of it) to allow for a records search.

Obliterated Serial Number on Firearm by Grinding

Serial number after restoration

In your novel you could consider using a gun that can be traced back to the killer, or his family, or a major crime (like a gun store robbery). The criminal or co-conspirator might then damage the serial number on the weapon before discarding it.  When your detective finds the weapon they can then take the above actions to restore it and discover the serial number. This is just the beginning of the search. The weapon may be decades old and have changed owners numerous times. The detective will have to hunt down each of those owners (if possible) and figure out who may have been responsible for the crime.  Each owner may spin the investigation off into a new direction and create additional obstacles for your protagonist to overcome.

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About forensics4fiction

Hi there. Thank you for visiting my BLOG for crime writers. I hope you will find it interesting. I would love to hear your questions and thoughts regarding forensics and criminal investigations. I hope that the information here will help answer your questions or ignite your imagination. I am a retired senior criminalist with 15 years of forensic experience. I have served as the president of the Association for Crime Scene Reconstruction, Rocky Mountain Association of Bloodstain Pattern Analysts, and the Rocky Mountain Division of the International Association for Identification. I am triple board certified in forensic related fields and one of only 40 board-certified bloodstain pattern analysts and 80 board-certified footwear examiners worldwide In addition to writing over 60 scientific papers, I have worked as the editor of the Journal of the Association for Crime Scene Reconstruction, been interviewed by and consulted for television, books, magazines, and newspaper articles including documentaries on the Discovery Channel and National Geographic.

Posted on September 9, 2011, in The Crime Laboratory and tagged , , , , , , , , , , , , , . Bookmark the permalink. 8 Comments.

  1. This is great!! Thank you very much.

  2. I need help. I have an old rifle that belonged to my father. I don’t know how long he had it. It was given to me by my mother about 2 months after he had died in 1975. I would like do some things with it. Like mount a scope and recoil pad. No gun shop will touch it because the serial number has been sanded or ground off. Theres some the serial still legible. Is there a process that can be used to bring the serial out. So I can have it restamped. Something like you mentioned (Fry’s reagent) Also can I do it myself or does someone else have to.

  3. Well Rodney, I’ m guessing the reason no gunsmith will touch it is that in the United States (if that’s where you are) it is illegal to even possess a weapon with a defaced serial number. I suggest you contact a lawyer to figure out how to proceed. I can’t help you with that.

  4. The serial has to be restored by a federally licensed firearms dealer in order to meet the specific marking requirements. If the firearm was manufactured before 1968, no serial number is required. If it was manufactured after 1968, technically you are in violation of federal law under 18 USC 922(k); but if you can prove ownership, you can submit a request to the ATF to reissue you a new serial number. They will give you a grace period to have a licensee engrave the new serial number. If you know where your father purchased the rifle, you can contact the dealer to see if they still have the records. That way you can get the proper serial number and prove ownership. If you do not wish to go through the hassle, you can always abandon the firearm to the local police.

  5. Thanks a lot for the information Terry. I had no idea a FFL dealer could do this for a customer. Usually when we got such a weapon in the lab it was heaed for the shredder. I appreciate you offering your advice to the readers.

  6. I just acquired an antique 1895 Winchester Lee Navy rifle that has all the metal buffed, leaving most hard to read…including the serial number. The area of the serial number is buffed smooth, except for the N.C.T. inspector stamp. My thinking is that it may be one of the 54 recovered from the USS Maine.
    Two questions…Is an antique with brushed away numbers illegal to own ?
    Where can I take it to try and restore the number to see if it may be such a historical piece ?

  7. Sounds like a great gun. I don’t give legal advice because I’m not a lawyer and I don’t know where you are and what laws apply to you but a local gunsmith would be the best person to talk to about the laws in your area and restoration of the number. However, refinishing of any kind might devalue the gun so if you care about the collector’s value you may want to talk to the gunsmith about how it might affect the value.


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