Bullet Revolutions Per Minute (rpm)
The general formula for calculating the rpm of a rotating object may be written as
where is the linear velocity of a point in the rotating object (in units of distance/minute) and C refers to the circumference of the circle that this measuring point performs around the axis of rotation.
For a bullet, the specific formula below uses the bullet's MV and the barrel's twist rate to calculate rotational speed:
- MV(in fps) x (12/twist rate in inches) x 60 = Bullet rpm
For example, a bullet with a muzzle velocity of 3050 ft/s fired from a barrel with a twist rate of 1 in 7-inch (180 mm) (e.g., the M16A2 rifle) spins at 313,714 rpm.
Excessive rotational speed can exceed the bullet's designed limits and the resulting centrifugal force can cause the bullet to disintegrate in a radial fashion.
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General Good is the plea of the scoundrel, hypocrite, and flatterer,
For Art and Science cannot exist but in minutely organized Particulars.”
—William Blake (17571827)
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—Henry David Thoreau (18171862)
“We are the men of intrinsic value, who can strike our fortunes out of ourselves, whose worth is independent of accidents in life, or revolutions in government: we have heads to get money, and hearts to spend it.”
—George Farquhar (16781707)