Inspiration for USS Missouri SBS-63's Foward Cannon

The Andromeda has dual forward cannons at the front of the ship.  The hexagonal shape of the cannon is what peaked my interest for the Missouri's single forward cannon.

The Yamato's forward cannon is almost completely in more rounded off shape, but more of a pentagon shape.

These two photos helped me arrived to having the forward cannon on the USS Missouri to having a hexagonal shape.

 Looking at the USS Arizona's forward cannon, its a hexagonal shape.  I used the top and side blueprints of the USS Arizona to help me shape out the hull.