Answer:
Rifling
Step-by-step explanation:
Within a gun's barrel, lands and grooves cause a bullet to spiral when exiting the barrel of the gun, much in the same way a football spirals when thrown. This Rifling pattern left on the bullet is unique to the firearm used to shoot the bullet.
Rifling refers to the spiral (helical) grooves that are cut or swagged on the internal surface (bore) of a gun barrel, which helps impart the spinning motion to a bullet when it's fired.