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1905, was the change over from I (infantry) to IS (Infantry Spizter) bore (or J to JS in American English). They (the German Military) moved to the .323″ diameter bullet, and JS, by the enlarging the rifle grooves but keeping the bore diameter (7.92mm) the same. As Glenn said, lots of commercial sporters, were made with .318″ grooves between the wars.
The change to the spitzer bullet design sent the US back the the drawing board. Changed the new 30 cal cartridge from 30’03 with a 220 grain bullet to the 30’06 with a 150-165 grain bullet.