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A Page from History: Air Resistance of a .30-'06

A Page from History: Air Resistance of a .30-'06

From the October 1957 issue of American Rifleman, a letter sent to the magazine asking about air resistance.

I know that when a bullet is fired at high speed, air resistance slows it down very fast, but could you give me an idea of how much the air resistance against the point of a .30-'06 military bullet amounts to in pounds?—N.S.P.

Answer: When the .30 cal. M2 bullet is fired at a muzzle velocity of 2700 fps, it takes .12 second to go to the first 100 yards, and during this brief interval it loses 219 fps, so that if it kept on losing speed at this rate, it would lose 1825 fps in one second.

When a bullet is dropped, gravity will give it a speed of 32 fps during the first second of its fall. Thus at this velocity air resistance changes the bullet's speed over 56 times as fast as gravity does. The force that gravity exerts on any object is equal to the weight of the object, and as a 152-grain bullet weights 1/46-lb., and as air resistance at the speed mentioned is 56 times gravity, it exerts a force of nearly 1 1/4 lbs. on the nose of the bullet.—J.S.H.

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