How Penetration Varies with Distance
Just discovered this nugget in a most unlikely source — in the chapter on measurement in Larrabee's "Reliable Knowledge." The "German ballistics expert" cited here was Dr Carl Cranz, whom scientific ballisticians have long considered "the father of ballistics," whose classic four-volume "Lehrbuch der Ballistik" (Handbook of Ballistics) is still the most important work on scientific ballistics ever published.
"A German ballistics expert, Professor C Cranz, set up some solid wooden targets made of cubes of beechwood that were one yard in all dimensions. He then fired ten identical bullets from an infantry rifle from the following distances, with these results:
[Can't reproduce the table here, alas — so I've omitted Column 1, which is just the list numbers for bullets 1 through 10; in each pair of numbers below, the first is the distance from the muzzle to the target, and the second is the depth of penetration in solid beechwood.]
6 feet — 12 inches
300' — 14"
400' — 16"
500' — 30"
615' — 28"
720' — 26"
1,313' — 16½"
1,850' — 10½"
2,885' — 5"
8,250' — 1.6"
"Similar experiments with cubical boxes of sand showed that the deepest penetration, 13 inches, was attained at a range of 1,050 feet. One would expect the penetration to be inversely proportional to the range; but this is not so, because the impact of the bullet at a high velocity flattens its shape to a larger cross-section and so impedes its entry. At the longer ranges it maintains its shape and reaches optimum penetration; then the inverse relationship begins."