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In order to make accurate predictions on gyroscopic drift several details about both the external and internal ballistics must be considered. Factors such as the twist rate of the barrel, the velocity of the projectile as it exits the muzzle, barrel harmonics, and atmospheric conditions, all contribute to the path of a projectile.
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.
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, traditionally speaking, most common method expresses the twist rate in terms of the 'travel' (length) required to complete one full projectile revolution in the rifled barrel. This method does not give an easy or straightforward understanding of whether a twist rate is relatively slow or fast when bores of different diameters are compared.
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.
As an example, when the barrel temperature rises and the bearing clearances change, the jump of the shot will change. This will affect the consistency. Similarly, the straightness of the barrel will affect the final trajectory and hence the accuracy, but it may also affect the shot pitch velocity at launch, which in turn may affect the consistency.
Schlieren High-Speed Video Of Shotshell Transitional Intermediate Ballistics. Transitional ballistics, also known as intermediate ballistics, [1] is the study of a projectile's behavior from the time it leaves the muzzle until the pressure behind the projectile is equalized, so it lies between internal ballistics and external ballistics.
Since Dutch roll is a handling mode, analogous to the short period pitch oscillation, any effect it might have on the trajectory may be ignored. The body rate r is made up of the rate of change of sideslip angle and the rate of turn. Taking the latter as zero, assuming no effect on the trajectory, for the limited purpose of studying the Dutch roll: