Many years ago, when the official histories of the desert fighting first came out, I was intrigued to see that in the special appendices on tank and anti-tank weapons, there was mention of the ranges at which various gun and ammunition combinations were effective against certain tanks, Up till then, the only source of information had been lists of penetrations achieved under test at various ranges, usually at 250 or 500 yard or metre intervals, and I hoped that the new information would help me to work out a system by which I could pinpoint the exact range at which penetration would occur. So I sat down, and calculated the vertical armour equivalent of the tanks concerned, making due allowance for slope, compared this with the penetration given in the tables, and then checked the distance at which penetration should theoretically occur against the distances at which the histories said that tanks could be knockedout. To my horror at the time, I found only the most general of resemblances. If I had stopped and thought about it in advance, this would have been less of a surprise. Penetration trials are carried out by shooting at flat plates of metal at a fixed angle, and the depths achieved by several shots is averaged out, no mention being made of the fact that individual shots of the group differed by up to 25%. The target is not resiliently mounted on a shock-absorbing suspension system, has no compound slope angles, corners, curves, protrusions, or weak spots caused by apertures, and in short, is not really very like a tank. Yet even today, wargames rules are still being based on graphs of theoretical penetrations, based on curves drawn by eye through an inadequate number of points, which are themselves only averages of a much larger scatter. The best known of these sets (no names, no packdrill!) goes so far as to have different curves for the American and British 75mm guns, almost identical weapons, firing identical ammunition! Others do not distinguish between tests carried out against plates at 30 degrees incidence arid those at zero incidence, and many do not appreciate that while the allies specify armour slopes as an angle from the horizontal, the Germans specified them as an angle from the vertical. Worse still, they treat ranges quoted in metres as being exactly the same as if they were quoted in yards, making for big errors at long ranges. A little knowledge can be a very dangerous thing! Another common mistake is to equate penetration with knocking-out. These are by no means the same thing. An AFV can be knocked-out without being penetrated and can be penetrated without being knocked-out. Examples of the first during the desert fighting were up-armoured Panzer III being knocked-out by delay-fused 25pdr H.E., and British tanks being put out of action by H.E. from the short 75 in Panzer IV. More recent examples include the T.55's knocked-out by American helicopters at Da Nang using 17pdr H.E. rockets for lack of H.E.A.T., and the recent demonstration when a 76mm H.E.S.H. round from a Saladin fired at a Centurion blew away two road wheels and half its track on one side, smashed every piece of optical and radio equipment, and although it did not completely penetrate the front armour, spalled enough fragments from the inside surface of the plate to have probably disabled or killed every crew member. Examples of weapons penetrating but doing relatively little damage have been frequent in Viet Nam, both American M-72 rocket launchers against PT-76, and Communist RPG-7 against M-113. Yet another point practically never taken into account is the trajectory of the weapon. Especially with low velocity weapons such as infantry rocket launchers, at long ranges, the majority of hits may well be on a tanks thin decking. At medium ranges, the missiles angle of descent may be enough to cancel out the slope of the armour, and at very short raniges, it may be possible to pick a Weak point as the target. Even he Tiger II, with its 200mm frontal armour basis, has substantial parts of its frontal armour less than 100mm thick. When writing our new rules for Armour 1925-50, we therefore made use of penetration figures only to collect the weapons used during the period into groups with similar capabilities. Much the same thing was then done with tanks with similar grades of armour protection. Once guns and tanks were sorted into Weapon classes and Armour Classes, we looked in the official histories for judgments as to the ranges at which a gun and ammunition in one of our Weapon classes, could be expected to penetrate a tank in one of the Armour classes, and then assumed this applied to all guns and tanks in those classes. We often had several examples in each class, and it was comforting to find that these agreed well with each other. Where there was no information because there had been no confrontation, for example, French 25mm A/Tank guns never to my knowledge faced "A" Armor targets, it was usually easy enough to fill in from context. Our last innovation was us recognize that there was no one range beyond which a target was safe, and below which it was completely vulnerable. We took two ranges, the highest at which the weakest part of the armour on that aspect of the tank could be penetrated, and the lowest at which the thickest part could be expected to stop a portion of the projectiles. Below the lower range we assumed complete vulnerability, above the higher, complete invulnerability. The probability of Penetration in the range band enclosed between the two ranges of course in real life increase as the range falls, but for the sake of simplicity we assumed that it would always be 50%, so that the target would be knocked-out if the score of a single dice was 4, 5 or 6. A different but similar method was used to evaluate knock-outs from non-kinetic energy weapons. Back to Table of Contents -- Wargamer's Newsletter # 131 To Wargamer's Newsletter List of Issues To MagWeb Master Magazine List © Copyright 1973 by Donald Featherstone. This article appears in MagWeb.com (Magazine Web) on the Internet World Wide Web. 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