If you are a police officer, you can trace a gun by accessing an ATF information system called “eTrace.”
The federal Gun Control Act of 1968 mandated that all firearms have a serial number and that everyone who buys a gun fill out federal Form 4473. The form records the name, address, driver’s license information and background check information of the buyer as well as the model and serial number of the gun. Licensed gun dealers are required to keep these forms for as long as they are in business, then surrender them to the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF).
Recover a gun you want to trace. Write down the serial number on the gun if it is available. If you are trying to trace a gun without a serial number, submit the weapon to the ATF where various techniques may be used to recover serial numbers that have been mechanically or chemically removed from legally manufactured firearms.
Log on to the eTrace website at https://www.atfonline.gov/etrace. Enter the manufacturer, type, caliber, barrel length and serial number of the weapon. The ATF answers critical trace requests within 24 hours.
Print out the ATF trace response. The one-page trace response will include the manufacturer, wholesale gun dealer and retail gun dealer who sold the weapon. The trace response will also list previous trace requests for the same weapon.
Go to the retail gun dealer who sold the firearm to a customer. Examine the Form 4473 for that weapon. Determine the first retail customer for that weapon.
Interrogate the first retail owner of the weapon. Determine if he sold the weapon and if he required the buyer to complete Form 4473. The last owner of a firearm to complete Form 4473 is usually called the “registered owner.”
New York, Maryland, California, New Jersey, and Massachusetts also keep detailed records, similar to the information recorded on Form 4473, of firearms sold in those states.
Firearms are sometimes sold in casual transactions without the completion of Form 4473.
Some firearms manufactured before 1968 or outside of the United States are not marked with serial numbers.