Ballistic Tests of Rifle Bullets

It was Dr. Fackler who found that gunshot wounds into swine flesh could be reproduced and calibrated in a mixture of 10-percent ordnance gelatin when maintained at 40°F. Thus a bullet that penetrated 7 inches in living flesh would equally penetrate 7 inches in Dr. Fackler's gelatin mixture, making ballistic tests much simpler and more valid.

Cpl. Ed Sanow of the Benton County, Indiana, Sheriff's Department used this gelatin mixture to conduct a series of rifle bullet ballistic tests in 1991, generating data and die photographs we're using here. All shots were fired at 10 feet.

Our greatest interest certainly is the .308 HPBT Match gelatin test, depicted in the photograph on page 158. Sanow found that the Sierra hollowpoint bullet snapped in two at the stress point where the lead filling ended, spawning two large projectiles that tumbled base-over-tip and carved an incredible wound channel, then followed separate paths until the heaviest fragment came to a hale 22 inches into the gelatin. The lighter hollowtip penetrated 16 inches of gelaun.

As the charts on page 159 note, this 6.4-inch temporary stretch is double that of pistol bullets, as well as other .223 and 7.62mm rifle bullets. Given this dramatic result, it's worth considering what happens when a bullet tumbles in a target.

By simple mathematics, we can determine that a .308 bullet having a muzzle velocity of 2,600 fps, when fired from a rifle having a 1:10 rifling twist, exits the barrel with a spin of 187,200 rpm—far more than most riflemen would ever guess. Rotating with more rpm than many gyroscopes, and flying supersonically nose-forward with an aerodynamically sleek boat-tail shape, it impacts. Then, suddenly, it's twisted sideways into a buzz saw blade fighting its own yaw and spinning more than 3,000 times per second. It twists and tears, and both pieces bounce against each other, like two supersonic razors hacking their way through tissue at the rate of the wildest whipsaw ever seen.

A split-second later, the two largest fragments split into separate paths. The recovered bullet base diameter was .59 inch, nearly double its original size, while Sanow found there had been a total of three to five significant fragments amounting to about half the bullet weight.

Thus, the Federal .308 HPBT Match bullet

5.56mm, 69-GR. MATCH GELATIN TEST. The lightweight, zippy bullet shattered, losing much energy and thereby lacked much penetration. {Photo credit: Ed Sanow, S.W.A.T. Magazine)

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