What are land and groove impressions?

Land and groove impressions refer to the distinct patterns left on a bullet as it travels through the barrel of a firearm, influenced by the rifling—a series of spiral grooves cut into the barrel. The rifling imparts a spin to the bullet, stabilizing it for better accuracy upon firing. Each firearm has a unique rifling pattern, including the width and depth of the grooves and lands. When a bullet is fired, these patterns leave characteristic impressions on its surface, which can be analyzed for forensic purposes. This analysis helps law enforcement link bullets to specific firearms, aiding investigations in criminal cases. Identifying these impressions is critical for ballistics experts when matching bullets to the weapon used in a crime.