SAAMI (Sporting Arms and Ammunition Manufacturer’s Institute) publishes standard twist rates for various cartridges. Manufacturer’s take care of this by building to accepted standards. The longer the bullet, the faster it must be spin to remain stable. It’s not the cartridge that determines necessary twist, but the bullet. What puzzles many shooters is exactly which twist they need for a specific cartridge. Shooters talk about twist rate a number of ways, but if asked “What’s your barrel twist?” most answer “It’s a one-in-ten twist,” or just “Ten.” What Rifling Twist Do You Need? A 3-inch barrel with 1:14” twist spins its bullets the same as if it were 14, 24 or 48 inches long. If the rifling grooves make a complete revolution in 9 linear inches, it is a 1:9” twist whether the actual barrel is 9 inches long, 30 inches long or just 3 inches long.A bullet traveling down a 12-inch barrel with a 1:14” rate of twist will still be spun at the 1:14” rate.
#RUGER RIFLING TWIST RATE CHART FULL#
A groove that turns at a degree sufficient to complete a full turn in 48 inches is a 1:48” twist rate regardless of barrel length. It’s the rate, angle or degree of the rifling twist, not the linear distance, that matters. A faster twist would turn a full circle in 14 inches of linear travel and a super fast twist would be one turn in 9, 8 or 7 inches.īarrel Length Doesn't Change Rifling Twist RateĪ 48-inch, slow twist barrel doesn’t have to be 48 inches long to work properly. A slow twist rate would make a complete turn in 48 inches of forward travel. This necessary spin rate is determined by the rifling’s rate of twist, which is the linear distance needed for the grooves to make one revolution. The longer the bullet, the faster it must be spun to remain stable in flight. Like a spinning top, a spinning bullet resists forces (in this case variable air pressure) from any side, so it better maintains its original flight vector. Even though musket balls can’t tumble, since they’re the same shape on all “sides,” they still fly straighter if spun. If an elongated projectile (bullet) didn’t spin, it would tumble. Why are rifled guns more accurate than smoothbores? Gyroscopic stability. Anyone who has shot slugs from a true smoothbore shotgun barrel and then switched to a rifled barrel understands the accuracy advantage, but might not fully understand why. Even shotguns can wear rifled barrels, which technically makes them rifles. Today rifled barrels are routinely used on handguns, cannons, rifles of all kinds and any barrel designed to spit a single projectile accurately. You can see a bit of a barrels rifling by looking at the end of the muzzle, but for a really good look you need the magnified view provided by a Hawkeye borescope. One of those was used to take the picture at the head of this article. The bullet's velocity and the degree or rate of the rifling's turning determines it revolutions per minute, which can be as high as 330,000 rpms. 224" bullets.īecause rifling grooves grip bullets so securely, the projectiles must follow the turning path of the rifling, and that's what gives them their spin. This is why 30-caliber cartridges are loaded with. Bullets fired down rifled bores must be slightly larger than bore diameter so they can be gripped or engraved by the rifling. To rifle a barrel means to put curving grooves into its bore.They can be cut in (cut rifling,) pressed in (button rifling) or hammered in (hammer forging). The word rifle comes from an old German word meaning to groove or furrow. If you wanted to shoot straight, you shot a rifled barrel. How Rifling Twist WorksĪfter our Revolutionary War, rifling became the best game in town. The British army was still shooting smooth bore muskets in 1776, a big part of the reason General Washington and his backwoods hunters shot them to pieces with their rifled flintlocks. True rifling, as we know it today, didn’t appear until the mid-1500s, and then it was probably used only in specialty guns because they were so slow to load. Primitive Rifling Twist First Triedīy the late 1400s, gun makers concocted the first crude rifling in an attempt to mimic the spin effect that fletching gave to arrows. Musket balls were cast smaller than bore diameter so they’d be easy to ram home, especially after one or two shots had layered soot down the barrel. Primitive blackpowder firearms spit balls from smooth bores and the words “accuracy” and “gun” weren’t used in the same sentence. And shooters have been confused about rifling twist rates ever since. Way back in the late 1400s an inventive gun maker added a new twist to firearms - rifling.