Ballistics

According to the ballistics report, this gun can't be the murder weapon.

Have you seen the results of the ballistics test?

The term "ballistics" refers to the study of a projectile in motion. Ballistics also refers to the forensic study of bullets, cartridges and firearms in criminal investigations. When a bullet travels through a gun barrel, the bullet's metal gets worn in a unique pattern by the harder metal of the barrel. Unless there has been some intentional alteration, any bullet fired by a specific gun will show the same marks.