Even if no bullets are found at the scene, the brand of bullet used in the crime can be determined by analyzing the small pieces of metal left behind.
Forensic experts may try to link a suspect to a crime by analyzing bullets or spent shell casings found at a crime scene and proving that they were fired by the suspect's gun. . But doing so when the bullet is not present at the scene, such as when it has been removed…
Source: www.newscientist.com