7,5 cm Pak 41 case was 545.1 mm long with 102.2 mm max diameter and 111.5 mm rim diameter, 7,5 Kw.K 40 case was 494.1 mm long, with 102.2 diameter and 111.5 rim diameter, so the7,5 cm Pak 41 case was generally longer, with slightly different dimensions of the front section as well.
Also it seems, the 7,5 cm Kw.K 40 cartridge could be inserted into the 7,5 cm Pak 41 chamber, but I think there was no real danger, as I don't think the Pak was electrically primed.
