Refined Penetration Estimates for T34 Tank Gun

[rexford]

Miles Krogfus has recently noted that Russian manuals for T34 indicate 655 m/s for 76.2mm APBC.

Based on 655 m/s muzzle velocity and analysis of U.S. firing trials with 100mm and 122mm APBC, an ARTKOM equation estimate for T34 76.2mm APBC against medium hardness rolled homogeneous armor is 81mm vertical at 0m. This is for BR-350B with typical heat treatment.

The 500m penetration would be 70mm of vertical homogeneous armor (medium hardness), for typical APBC, which is inadequate against Tiger side 82mm plate unless plate is "bad".

With special heat treatment BR-350B, the 400m and 600m penetration would be 79mm and 74mm homogeneous, which would square with some reports of T34 penetrations at 400m and bouncers at 600m.

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U.S. firing trials with 122mm APBC resulted in 127.5mm vertical penetration at 655 m/s, against medium hardness rolled homogeneous armor.

Applying the ARTKOM equation to the 122mm APBC penetration at 655 m/s, the C constant for 122mm APBC is 2380. If the same constant is applied to 76.2mm APBC (BR-350B) at 655 m/s, the 0m vertical penetration for the T34 tank gun is 81mm.

81mm penetration at 0m and vertical would make penetration of the Tiger 82mm side armor difficult at any range and angle.

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The U.S. firing trials with 100mm APBC can also be used to estimate 0m penetration for 76.2mm BR-350B, and the result is 82mm vertical.

Because the U.S. tests with 100mm APBC were against cast armor, they were converted to homogeneous plate using the equation we developed for good quality cast and rolled armor. Examining the results, it appears that the U.S. cast armor contained additional deficiencies, based on comparison with British tests of a captured SU 100 and ammunition (John Salt site, report DEFE 15/1107):

0m Penetration Comparison

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30 degrees, 164mm rolled (British), 165mm rolled cast equivalent (U.S.)

45 degrees, 133mm rolled (British), 151mm rolled cast equivalent (U.S.)

60 degrees, 96mm rolled (British), 104mm rolled cast equivalent (U.S.)

70 degrees, 59mm rolled (British), 62mm rolled cast equivalent (U.S.)

Rolled cast equivalent is after the cast thickness has been converted to rolled thickness, and the above figures suggest that the cast armor was not highest quality.

915m Penetration Comparison

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30 degrees, 140mm rolled (British), 150mm rolled cast equivalent (U.S.)

45 degrees, 115mm rolled (British), 135mm rolled cast equivalent (U.S.)

60 degrees, 84mm rolled (British), 88mm rolled cast equivalent (U.S.)

70 degrees, 51mm rolled (British), 52mm rolled cast equivalent (U.S.)

U.S. cast armor in the 100mm to 127mm thickness is 5% to 17% less resistant then it should be, which suggests flaws or other problems with penetration resistance.

At 655 m/s, the 100mm APBC penetrates 5.08" of U.S. cast plate, which is equivalent to 4.95" using a cast-to-rolled armor deficiency equation. This thickness would be reduced by 10% to model additional penetration resistance problems with the castings.

100mm APBC at 655 m/s would have an ARTKOM constant of 2356 against medium hardness rolled armor, which is similar to 122mm APBC.

Applying the 2356 C constant to the ARTKOM equation for 76.2mm BR-350B at 655 m/s results in 82mm of vertical RHA at 0m.

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It should be noted that the ARTKOM equation C constant for APBC against rolled homogeneous armor plate varies with velocity and is not a true constant. While the ARTKOM equation assumes that penetration varies as velocity raised to 1.43 power, the U.S. tests with 122mm APBC showed the penetration to vary as the velocity raised to the 2.5 power down to 671 m/s, and to the 1.8 power below that.

[Jeff Duquette]

So it appears that that your original velocity estimates for the 76mm F-34 firing BR-350B were in fact incorrect. I believe I indicated this to you several months ago on this forum and suggested that you research this further.

So what are your penetration estimates for 1000m and 2000m for F34 firing BR-350B, and can you provide a sample calculation as to how exactly you are arriving at either the 1000m or 2000m figure?