The big problem for Germany with the taper bore was the eventual running out of Tungsten supplies required for ammunition production. The 'squeeze bore' is a slightly different thing, the gun only tapers for the final length of the barrel such as in the PAK 41 where the last section of the barrel was a detachable squeeze that could be easily replaced.
Cheers,
Adam

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"Wars cannot be fought with dream stuff" - Sir Percy Hobart.