Panzerkampfwagen IV with Panther Schmalturm
Drawing by H. L. Doyle from Panzerkampfwagen IV and Its Variants, 1975.
Given the growing resistance of allied tanks to
German anti-tank guns, plans were developed to categorically
up-gun the entire range of German tanks toward the end of
World War II. One possible answer was affixing the Schmalturm
of the Panther Ausf. F to the Panzerkampfwagen IV Ausf. J chassis.
The drawing above gives a good indication of what the conversion
would look like.
Unfortunately, like so many other late-war German
projects, this conversion was impractical. The chassis of the
panzerkampfwagen IV was severely overloaded by the schmalturm.
Furhtermore, it is doubtful the turret ring of the Panzer IV would
have been able to accomodate the turret unless the overhang was
widended (which was suggested in one schematic). However this
would have further overloaded an already burdened chassis.
Source: Panzerkampfwagen IV and Its Variants