That is what I thought as well........naval rifles since they were actually rifled barrels.The Navy called the 16" guns on the battleships rifles...
I've been sick the past few days and have been watching YouTube movies. "The Battle of Archimedes" is a Japanese made flick that is centered around the design/politics/construction/sinking of the battleship Yamato. The opening scenes alone are worth watching.
The Yamato, even though is sits at the bottom of the Pacific, is still to this day a source of pride to the Japanese people, and it has become part of their cultural lore......with it's 18" guns!