re: Major WWII shipwreck discovered: Japanese battleship sunk by US found

After the war they tested the armor of Yamato's never-finished sister ship against the Iowa's 16 inch guns. The Iowa's AP ammo had nearly as much penetrating power as Yamato's's 18 inch shells and it could fire 3 salvo's per minute vs Yamato's two. The Iowa class was also faster and could fire accurately while maneuvering at full speed, which the Yamato couldn't do.

Of course both were already obsolete when they were built.