What is the correct term for the grooves inside a firearm's bore that improve bullet accuracy?

The correct term for the grooves inside a firearm's bore that improve bullet accuracy is rifling. Rifling refers to the spiral grooves that are machined into the barrel of a firearm. These grooves cause the bullet to spin as it travels down the barrel, stabilizing its flight path and improving overall accuracy. The spinning motion helps to counteract various forces that can affect the bullet's trajectory, such as air resistance and gravitational pull, thereby enhancing precision during shooting.

The other terms provided do not accurately describe the concept of grooves in a firearm's bore. Barrel threading refers to the practice of cutting threads into the barrel for attachment of muzzle devices, which does not contribute to bullet stability or flight. Barrel expansion does not relate to groove patterns affecting accuracy; rather, it might refer to the physiological response of a barrel to heat or pressure. Gun sight alignment focuses on the aiming mechanism of a firearm, which is separate from the barrel's internal features meant to stabilize the projectile in flight.