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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.
Rifling of a 105 mm Royal Ordnance L7 tank gun Conventional rifling of a 90 mm M75 cannon (production year 1891, Austria-Hungary) Rifling in a GAU-8 autocannon. 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.
Another issue that has an effect on the barrel's hold on the bullet is the rifling. When the bullet is fired, it is forced into the rifling, which cuts or "engraves" the surface of the bullet. If the rifling is a constant twist, then the rifling rides in the grooves engraved in the bullet, and everything is secure and sealed.
The rest of the barrel was maintained at the original thickness to enable the M203 grenade launcher to be attached. The barrel rifling was revised to a faster 1:7 (178 mm) twist rate to adequately stabilize the new 5.56×45mm NATO SS109/M855 ball and L110/M856 tracer ammunition.
A gain twist has a slow initial twist in the barrel, progressively getting faster until the final twist rate is attained near the muzzle, resulting in less torque being imparted to the bullet during the highest stress phase of the interior ballistic cycle, and thus less wear in the throat of the barrel. Gain twist was phased out in the last ...
Bullets in this caliber are hard to find but provide greater weight than .223 caliber bullets, up to 100 grains (6.5 g), without excessively quick twist rate. The .257 Roberts Ackley Improved is a second generation wildcat cartridge based on the .257 Roberts cartridge.
Common rifling twist rates also often have to be tightened to stabilize very long projectiles. Such commercially nonexistent cartridges are termed "wildcats". The use of a wildcat-based (ultra) long-range cartridge demands the use of a custom or customized rifle with an appropriately cut chamber and a fast-twist bore.
The Integral Silencieux barrel has an integrated suppressor. The 7.62×51mm NATO and .300 Savage barrels feature a 305 mm (1:12 in) right-hand twist rate. The twist rate for the other standard chamberings are; 7mm-08 Remington 241 mm (9.5 in), .260 Remington 229 mm (9 in), and 6.5×47mm Lapua 203 mm (8 in). The Intervention barrels are ...