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Rexford/Bird Scaled Penetration Formula
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Rexford/Bird Scaled Penetration Formula
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This formula was found on page 78 of Rexford and Bird's WWII Ballistics: Armor and Gunnery (2nd Edition), and lets you estimate the penetration of a scaled up or down round using a variant of the DeMarre equation. The formula as reproduced from the book, is:
Where:
PScale: Estimated Penetration of scaled round
PRef: Penetration of Reference Round
VScale: Velocity of Scaled Round
VRef: Velocity of Reference Round
DScale Diameter of Scaled Round
DRef: Diameter of Reference Round
WScale Weight of Scaled Round
WRef: Weight of Reference Round
BIG NOTE: Because the penetration scaling formula works off ratios, it's possible to mix and match metric and imperial units. You can verify this by examining an excerpt of the page in question from WWII Ballistics, where they give an example using shell diameter in millimeters, weights in pounds, velocity in ft/sec and penetration in millimeters.
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