rifling

Rifling is the pattern of helical grooves cut or formed into the bore of a firearm barrel. The grooves, together with the adjacent lands, grip the projectile and cause it to spin as it travels down the barrel. This spin stabilizes the bullet gyroscopically, reducing yaw and improving accuracy and effective range compared with smoothbore barrels.

Most rifling uses a right- or left-hand twist, meaning the projectile completes a full rotation after a certain distance within the bore. The twist rate, expressed as the distance required for one turn (for example, 1:10), must be matched to the bullet’s length and velocity to achieve stable flight. Bullet design, seating depth, and muzzle velocity all influence performance with a given twist.

Rifling patterns vary. Conventional land-and-groove rifling is common, but polygonal rifling—where the bore surface is formed with rounded, polygonal interfaces—also appears in some firearms. Different manufacturing methods exist to create rifling, including cut rifling, button rifling, hammer forging, and polygonal processes. Each method affects bore finish, wear characteristics, and gas seal with the projectile.

History and use: rifling emerged in Europe during the 15th–16th centuries and was widely adopted in military firearms by the 19th century. Modern rifles and many handguns rely on rifling to achieve accuracy at longer ranges. Maintenance considerations include managing bore fouling and erosion, which can degrade accuracy if not addressed through cleaning and proper lubrication.