Global InformationRifling information
Rifling is the term for helical grooves machined into the internal surface of a firearms's barrel for imparting a spin to a projectile to improve its aerodynamic stability and accuracy. It is also the term (as a verb) for creating such grooves.
Rifling is measured in 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 cm)). A shorter distance/lower ratio indicates a faster twist, generating a higher spin rate (and greater projectile stability and accuracy).
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).[1] 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), use twist rates of 1 turn in 8 inches (20 cm) or faster.[2]
Rifling which increases the twist rate from breech to muzzle is called a gain or progressive twist; a rate which decreases down the length of a barrel is undesirable because it cannot reliably stabilize the projectile as it travels down the bore.[3][4]
An extremely long projectile, such as a flechette, requires impractically high twist rates to stabilize; it is often stabilized aerodynamically instead. An aerodynamically stabilized projectile can be fired from a smoothbore barrel without a reduction in accuracy.
- ^ Smith, Randy D. "The .54 Caliber Muzzleloader". Chuck Hawks. Archived from the original on 2008-08-11. Retrieved 2008-08-19.
- ^ "Products::Rifle Barrels::Calibers and Twists". Shilen Rifles, Inc. Archived from the original on 2007-09-27. Retrieved 2008-08-19.
- ^ "gain twist". MidwayUSA GunTec Dictionary. Archived from the original on 2009-02-15. Retrieved 2008-08-19.
- ^ Lilja, Dan. "What makes a barrel accurate?". Archived from the original on 2007-08-30.