How are striations internal ballistics created?

Striations in internal ballistics are created by the interaction between the projectile (such as a bullet) and the barrel of the firearm during firing. As the bullet travels down the barrel, the rifling—spiral grooves cut into the barrel—imparts a spin to the bullet, which causes it to engrave unique markings or striations on its surface. These striations result from the bullet's contact with the barrel's metal, where variations in the barrel's surface and the bullet's material can create distinct patterns. These markings can later be used for forensic analysis to match a bullet to a specific firearm.