What term describes the striations on a bullet after it passes through a barrel?

The correct term describing the striations on a bullet after it passes through a barrel is "rifling." Rifling refers to the grooves and lands that are created inside the barrel of a firearm. When a bullet is fired, it engages with these grooves and is imparted with a spin, which stabilizes its flight path. This interaction also leaves unique striations on the bullet, which can be examined later to match it to a specific firearm.

"Signature," while it might imply a unique identifier, does not specifically relate to the physical characteristics imparted on a bullet by a barrel. "Marking" is too general and does not specifically describe the internal characteristics of a firearm. "Ballistic imprint" is also a term associated with the markings left on bullets and cartridge casings but does not specifically denote the striations themselves caused by rifling. Thus, the term "rifling" accurately captures the specific phenomenon of striations created by the barrel's internal structure.