How Penetration Varies with Distance

[Ken Howell]

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."

 

[Brent]

Just an observation of mine in the field the last few years, hunting with factory loaded Swift A-frames in my 416wby. I shot a moose at 220yds missing the spine and breaking the opposite shoulder blade only.

The moose fell and never moved again. The bullet stopped under the skin and retained 365gns of 400, mushroomed perfectly at .700-.750" dia.

The other moose was shot at 640yds and missed the mark a little, taking out both front shoulders then exiting with surprisingly little meat lost.

I now hunt long range with the high BC Barnes 400 XLC`s as they are flatter and offer possibly less damage to meat. It seems after maybe 500yds any bullet would likely exit,

less frontal area resulting from lower impact velocity = higher psi on receiving tissue = deeper penitration. Nice to see a chart like his, gives me alot better idea how well they do at 1000+yds when I enter that phase.

I assume 5" of penitration at 3000 feet is with quite a low powered cartridge though. Was there any mention of vel. or bullet weight in there?

Thanks for the insight Ken.