MYTH: Criminals can easily alter a gun’s fingerprint with a nail file.
FACT: While it is possible to alter the fingerprint, it is not easy and it is extremely rare. First, the criminal would have to file down at least 6 places on the gun to successfully alter the signature (breech face, ejector, chamber, ejection port, firing pin, and extractor).(2) Second, ATF has found that this type of activity is virtually unheard of – the authors of a recent ATF report, with decades of experience, could recall only ONE successful attempt to alter a weapon.(3)
MYTH: Criminals could evade detection by changing the barrel or firing pin of the gun.
FACT: They could, but they won’t. As the ATF report suggested, criminals simply do not go to these lengths to avoid detection.(4) Moreover, no crime-fighting technology is foolproof – fingerprints themselves can be thwarted by criminals who wear gloves.

Do you know what puts the tracable markings on the bullet? The barrel--nothing else.