What occurs when a bullet is scored by the barrel markings of a firearm?

When a bullet is scored by the barrel markings of a firearm, it results in groove impressions and striations on the bullet. This phenomenon occurs because the unique features of a gun's barrel, including its rifling, leave specific patterns on the bullet as it is fired. Each firearm has a distinctive barrel pattern, which means that these marks can be used to help determine the specific firearm that fired a particular bullet.

Groove impressions refer to the broader patterns left by the lands and grooves of the firearm's rifling, while striations are microscopic scratches that occur on the bullet as it travels through the barrel. This combination of characteristics can be crucial in forensic ballistic analysis, allowing experts to link a bullet to a specific weapon. Therefore, the correct identification of groove impressions and striations is essential in crime scene investigations and can play a vital role in determining firearm-related evidence in legal cases.