A one round per 6 minute firing ratio doesn't give one much time to adjust their aim. The mortar has to aim at where the ship is anticipated to be at and a good skipper will chase the shells (USS Portland did this in the Battle of the Komandorski Islands) to avoid incoming fire. Naval gunnery with direct fire is a difficult art.

The International Naval Research Organization (INRO) has published numerous articles on battleship gunnery. Anyone interested in reading them should contact them for back issues.