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Thus the optimum rate of twist for this bullet should be approximately 12 inches per turn. The typical twist of .30-06 caliber rifle barrels is 10 inches per turn, accommodating heavier bullets than in this example. A different twist rate often helps explain why some bullets work better in certain rifles when fired under similar conditions.
Civilian AR-15 rifles are commonly found with 1 in 12 inches (30 cm) or 54.8 calibers for older rifles and 1 in 9 inches (23 cm) or 41.1 calibers for most newer rifles, although some are made with 1 in 7 inches (18 cm) or 32 calibers twist rates, the same as used for the M16 rifle. Rifles, which generally fire longer, smaller diameter bullets ...
The .308 Winchester has slightly more drop at long range than the .30-06 Springfield, owing to its slightly lower (around 30 metres per second (100 ft/s)) muzzle velocity with most bullet weights. Cartridges with significantly higher muzzle velocities, such as the .300 Winchester Magnum can have significantly less drop at long range, but much ...
Rifling twist: 1 in 12 in (304.8 mm) ... .22 caliber, cartridge with two bullets per cartridge ... in terms of hit rates and terminal ballistics, ...
Both of these variants were chambered in the 7 mm caliber developed by Mauser, and the barrel had 4-groove rifling with a right-hand twist. [6] The rifling twist rate was 1 revolution in 8.68 inches (220 mm). [11] The 7 mm ammunition was fired at a muzzle velocity of 2,330 feet per second (710 m/s) from the standard rifle-length barrel. [11]
The fact that the .243 Win was originally offered in a 1 in 10 inch rifling twist rate, a rate better able to stabilize heavier, 100- and 105-grain bullets, versus the .244 Remington's 1 in 12 inch twist (hence the 90-grain factory offering) was also a factor in their popularity.
Early production rifles had a 1:12 twist rate and post-2014 rifles have the 1:9 twist rate. [2] The CZ 527 Varmint in .223 has muzzle velocities for standard-load 45-grain (2.9 g) ammunition of around 3,500 feet per second (1,100 m/s). The 1:9 barrel twist in the Varmint Kevlar reduces muzzle velocities by about 1.5%.
In recent times 75-grain (4.9 g) .224" bullets have been developed for use in high velocity .22 caliber rifles for taking larger game and long-distance shooting. Heavier bullets perform best in rifles that have an appropriate rifling twist rate taking into consideration the diameter, length, and other physical properties of the projectile.