20 Inch Naval Gun

First off... NO!

This was a concept never followed upon in the real world, but has poked up on NS before. Originally designed by a US Civil War captain as a shore battery, there were a total of three 20" Rodman Guns constructed.

In the RL WWII, the concept of shipbourne 20" cannon appeared, and was in planning for the both the United States Navy Montana Class Battleship and for the unnamed Imperial Japanese Navy superbattleships. However, when the war ended, no keel had been laid, and the age of the Aircraft Carrier had already begun. The plans for the 20" Gun battle-wagons were scrapped, and the largest naval gun conceived never saw production.

Had it been created, the 20" Naval Gun would have fired a half-ton shell at unknown ranges. If you wish to possess a large caliber naval gun, the 16 Inch Naval Gun or 18 Inch Naval Gun should suffice. It is more effective to drop 5000lb bombs from aircraft than to fire 5000lb shells from a behemoth like the cancelled Superbattleships.