Were there any larger caliber naval guns during WW2, than the 18.1 inch guns of the Japanese battleship "Yamato"?
No. Atleast no conventional gun. But both Japan and German had plans to use larger guns in their next generation battleships. Japanese even built one or two 20.1" gun but nothing more came about this plan.
Were there any coastal defense of artillery guns larger than 18 inch. I thought the Germans had a huge railway gun called the "Paris Gun", or somthing.
As far as I know, the largest land artillery was the German 80cm. The Germans also built a 21in naval gun that served in trials. The Japanese designed but never completed a 51cm gun. A 48cm gun built before the Washington Treaty survived at Kamegakubi Proving Ground to the end of WWII.
