Ben,
9.3x74R cases can be reformed to the head diameter you need,I too understand Buffalo Arms does this.To do it yourself, you will need a hydraulic press(a loading press isn't powerful enough)and a lathe(to make the necessary dies,turn the rim, and turn a groove ahead of the rim to avoid closing the primer pocket).I have a little experience doing this type of reforming,if you want to go to the trouble,let me know.
Mike