Rifling

Uncommon card · No. 79839

Rifling is the term for helical grooves machined into the internal surface of a firearm's barrel for imparting a spin to the fired projectile to improve its aerodynamic stability and accuracy. It is also the term (as a verb) for creating such grooves. Firearms without rifling are called smoothbore. Rifling is measured by twist rate, the distance the rifling takes to complete one full revolution, expressed as a ratio with 1 as its base (e.g., 1:10 inches (25.4 cm)). A shorter distance/lower ratio indicates a tighter twist, generating a higher spin rate (and greater projectile stability). The combination of length, weight, and shape of a projectile determines the twist rate needed to gyroscopically stabilize it: barrels intended for short, large-diameter projectiles such as spherical lead balls require a very low twist rate, such as 1 turn in 48 inches (122 cm). Barrels intended for long, small-diameter projectiles, such as the ultra-low-drag 80-grain 0.223 inch bullets (5.2 g, 5.56 mm),...

Read on Wikipedia · Image baku13, CC BY-SA 3.0