I think Mr Gardner has just about answered it, thanks for that. So an incline of 60 degrees effectivley doubles the armours thickness, what is the incline on the armour of a Panther again?

I am guessing that the type of ammunition being fired at the tank must also be taken into consideration, I mean non penetrative ammunition (the equivilant of HESH) would have a different effectivness when fired at 60mm of armour than AP etc.

One other thought, how about ammunition glancing of armour, I have read accounts of rounds hitting the armour of a Hetzer but the incline of the armour at the front caused the round to glance off and do very little damage. I was just wondering whether this was actually a design feature so much as a useful side effect.

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There's no honorable way to kill, no gentle way to destroy. There is nothing good in war. Except its ending.