Basis of German Penetration Data

[rexford]

Quite a few books, including Encyclopedia of German Tanks of WW II and Thomas Jentz' Panzertruppen, have published 30 degree penetration data for German weapons. The basis for the data can be found in the British BIOS report GERMAN STEEL ARMOUR PIERCING PROJECTILES AND THEORY OF PENETRATION, and it provides some interesting twists that are vital to proper use and understanding of the data for APCBC rounds (the thickness penetrated on half the hits should exceed the listed 30 degree figures).

1. German data is based on penetrations with HE burster intact and useful

2. An equation in abovestated BIOS report was used by Germans to estimate penetration at 30 degrees from vertical

3. Estimates are for best quality projectiles (specially made for tests or very best deliveries from standard production), where penetration estimates for average production ammo would require higher velocities to defeat a given thickness according to following figures:

a. 5% higher for 75mm

b. 3.5% higher for 88mm, 105mm and 128mm projectiles

4. Penetration versus velocity curve for 75mm, 88mm and 105mm projectiles based on obtaining five consecutive hits within a velocity range which result in a success (round passes completely through plate with HE burster intact).

5. The penetration resistance of German plate appears to vary quite a bit as hardness changes

6. The German critical velocity Gd is based on the criteria noted in note 4. above

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To obtain five consecutive successes within a narrow velocity range as velocity increases, the probability that each round will succeed must be very high. For an 85% probability that five rounds will succeed in a row, the individual shots would each have an average 97% success rate. This means that German data is not comparable to American and British penetration data that uses 50% success as the criteria.

To convert the German data to 50% success, the thicknesses would have to be increased by at least 10% (and possibly as high as 15%, subject to standard deviation size), which increases the penetration thicknesses above those shown on the tables even when the decrease to production ammo is considered.

With regard to German armor hardnesses, the curves do not reflect the sudden changes in resistance which could occur as plate hardness changes in a step function with thickness variations.

BIOS is the British Intelligence Objectives Sub-Committee, and the abovementioned report is BIOS FINAL REPORT No. 1343, ITEM No. 2, dated September 1945.

The BIOS mission sent groups to Germany after the war (and maybe during the final stages as key areas were captured), interviewed key German personnel and collected published materials.

30 degree penetration estimates from equation in BIOS report follow for best quality ammo used in tests:

75mm APCBC

146mm at 935 m/s (Panther muzzle velocity)

140mm at 918 m/s (Panther ammo at close to 100m)

100mm at 710 m/s

88mm APCBC

200mm at 1003 m/s (88L71 at 0m)

180mm at 939 m/s

160mm at 886 m/s

140mm at 829 m/s

120mm at 763 m/s (Tiger 88L56 at close to 100m)

100mm at 680 m/s

[rexford]

The German equation for 30 degree hits (from vertical) is of the form:

velocity in m/s = C' x (diameter in centimetres/weight in kg)raised to 0.5 power x (plate thickness in decimetres)raised to 0.8 power.

For 75mm APCBC, C' varies according to following table:

Thickness..................C'

80mm......................722

100mm.....................710

120mm.....................690

140mm.....................668

160mm.....................640

180mm.....................628

200mm.....................628

220mm.....................655