Thats not what I am saying.....for example, the gun in the panther was a 75mm kwk 42/L70......as I understand it the 70is how long thegun tubeis.
the gun in the king tiger was a 88mm kwk 43/ L71.....so the kt had agun tube lenghof71

one of the proposed guns for the july 45 king tiger was the 105mm kwk /L68......that isthe gun tube would be 68 long....

the e75 in the kithas lenght 100.......that gun was never never designed for a tank as far as I have read....just think about driving that thing in a town.....you would be sticking it through wondows on every turn.