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The C.I.P. recommends a five groove barrel contour with each groove having an arc length of 5.33 mm (0.210 in) and a twist rate of one revolution in 406 mm (16.0 in). The recommended pressure for the .505 Gibbs is 2,700 bar (39,000 psi).
While standard rifle barrels taper from breech to muzzle, high precision rifles will often use a barrel with far less taper, called a heavy barrel, sometimes leaving the barrel cylindrical all the way to the muzzle, called a bull barrel. Either technique greatly increases the stiffness of the barrel by enlarging the average diameter, but this ...
SAAMI recommends a barrel rifling contour of 6 grooves with a bore Ø of .2505 in (6.36 mm) and a groove Ø of .257 in (6.5 mm) with each groove being .098 in (2.5 mm) wide. The recommended optional twist rate is one revolution in 10 in (250 mm). Both SAAMI and Weatherby recommend a freebore of .378 in (9.6 mm).
The Springfield Armory XD-M (with 'M' standing for match) features components that were more advanced than those of the regular XD pistol, such as sights and the barrel, which are deemed match grade. The magazines have extended capacities for target or combat shooting and the slide also has a more durable melonite finish.
Twist rate is given as 1 in 16 by Weatherby which would stabilize bullets up to 600-grain (39 g) and mono-metal bullets. Weatherby provides a six-groove contour No. 4 barrel for the .460 Weatherby Magnum. Ø land is given at .450 in (11.4 mm) and Ø groove is .458 in (11.6 mm).
Conventional eight groove rifling on the left, and octagonal polygonal rifling on the right. Polygonal rifling (/ p ə ˈ l ɪ ɡ ə n əl / pə-LIG-ə-nəl) is a type of gun barrel rifling where the traditional sharp-edged "lands and grooves" are replaced by less pronounced "hills and valleys", so the barrel bore has a polygonal (usually hexagonal or octagonal) cross-sectional profile.
The CZ 455 Varmint is fitted with a 20.5 inches (520 mm) heavy-contour "bull" barrel designed to increase accuracy, and weighs 3.2 kilograms (7.1 lb). The Varmint uses the same high-comb Turkish walnut stock of 455 American, and is designed solely for use with telescopic sights.
The length of the barrel (especially for larger guns) is often quoted in multiples of the caliber, used, for example, in US naval rifles 3 in (76 mm) or larger. [2] The effective length of the barrel (from breech to muzzle) is divided by the barrel diameter to give a dimensionless quantity.