Rifling, which first made an appearance in the 15th century, is the process of making grooves in gun barrels that imparts a spin to the projectile for increased accuracy and range.
Charles T. James developed a rifled projectile and rifling system.
The rule of thumb that Greenhill devised based upon his formula is actually what is seen in most places, including Wikipedia.
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So our rifling should be roughly 12" per turn. The twist, as listed on Wikipedia's .30-06 article is 10" inches per turn as an average of .30-06 caliber rifles; thus 12" inches per turn is fairly accurate.
The widely adopted solution, invented in 1863 by William Palliser, consisted of enlarging the bore to accept a wrought iron tube (called the A tube) into which the rifling had been cut.
Shots fired at higher velocities may cause severe leading of the rifling and of the forcing cone, introducing a potentially dangerous condition from overpressure if FMJ (Full Metal Jacket) bullets are subsequently fired without first removing the lead buildup.