rexford Posted March 19, 2004 Share Posted March 19, 2004 The World War II penetration data figures presented in the CM games appear to represent the 50% success thickness that can be defeated. If a gun with 82mm penetration hits an 82mm plate flat on, half the hits get completely through and half don't. The 50% success criteria averages the highest velocity that results in a failure with the lowest success velocity. The penetration probability curve is a bell shaped normal distribution, and actual "standard deviations" for the curve against good armor range from 4% during U.S. trials with 37mm APCBC to 7% for Russian 76.2mm APBC ammo. Firing tests against Tiger resulted in a "standard deviation" of 5.65%. The "standard deviation" indicates the spread of the curve, where 68% of the results are within one "standard deviation" (plus or minus) from average. If half the hits succeed when the penetration equals the armor effective resistance (after quality multipliers and slope effects), then the following table applies: penetration equals armor resistance, 50% success penetration -0.5 std deviations less than resistance, 31% success penetration -1 std deviations less, 16% success penetration -1.5 std deviations less, 7% success penetration -2 std deviations less, 2% success penetration -2.5 std deviations less, 0.6% success penetration -3 std deviations less, 0.1% penetration 0.5 std deviations over resistance, 69% success penetration 1 std deviation over resistance, 84% success penetration 1.5 std deviations over, 93% success penetration 2 std deviations over, 98% success penetration 2.5 std deviations over, 99.4% success penetration 3 std deviations over, 99.9% success Actual firing tests against the Tiger side armor by the Americans, British and Russians show an average resistance of 84.5mm with a standard deviation of 5.65%. The 84.5mm takes into account thickness variations above the 80mm design spec and ballistic advantages. If the Sherman 75mm hits the Tiger side armor at 750m range with APCBC and no side angle, the penetration is 77mm and the armor resistance is 84.5mm. The penetration is 8.88% less than the resistance. With a standard deviation of 5.65%, the Sherman penetration is 8.88/5.65 or 1.57 standard deviations below the resistance. The penetration probability works out to 5.8%. Reports on the combat where Michael Wittmann's Tiger was knocked out suggest that Sherman 75mm APCBC rounds were bouncing harmlessly off the Tiger side armor at 700 to 800 yards, which could be a function of inadequate penetration at range, side angles to the shots and "unlucky rolls". If the standard deviation for the 750m hit on the Tiger side armor was 4% or 7%, the corresponding penetration probabilities would be 1.3% and 10.2%. Poor or flawed armor not only reduces the effective resistance of armor, but the standard deviation appears to be about 60% greater than the figure which would apply to good armor (quality = 1.00). When rounds do defeat armor despite less penetration than the resistance and the penetration probability is very low, chances are good the round will have little remaining energy when it passes through the armor, and the shell structure may be sufficiently damaged to prevent the HE burster from going off. At Kursk, one of several 76.2mm hits on the side of a Ferdinand made it into the vehicle but did little damage. 0 Quote Link to comment Share on other sites More sharing options...
John Kettler Posted March 20, 2004 Share Posted March 20, 2004 rexford, Please see my reply in the cross posted CMBB thread. Hunted all through what the board search engine gave me on the info cited, but came up totally blank. This shouldn't have happened, because I know full well I made the post. Let's say that I'm terminally underwhelmed with the InfoPop excuse for a search engine. Regards, John Kettler 0 Quote Link to comment Share on other sites More sharing options...
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