The Evolution Of The Rifle

Bullets leaving a rifled barrel can spin at over 100,000 revolutions per minute (rpm) depending on the muzzle velocity of the bullet and the pitch of the rifling. The rotational speed of the bullet can be calculated by using the formula. The formula divides the number of inches in a foot (12) by the rate of twist that the barrel has. This number is multiplied by the muzzle velocity (MV) and the number of seconds in a minute (60). For example, a bullet with a muzzle velocity of 3,000 feet per second (910 m/s) leaving a barrel that twists once per foot (1/12") would rotate at 180,000rpm.
MV x (12/twist rate in inches) x 60 = Bullet RPM
Example using a barrel that has a twist rate of 1 turn in 8" with a muzzle velocity of 3000 ft/s: