Gun caliber eventually loses to rate of fire

How did the rate of fire of 15-inch guns compare with proposed 18- or 20-inch weapons?

Fifteen-inch guns could fire much faster, while very large calibers imposed severe shell-handling, machinery, and barrel penalties.

Triple 15-inch guns could sustain substantially more fire than 18-, 20-, or 24-inch weapons because every round and handling mechanism was lighter. The estimate puts the rate-of-fire advantage at roughly 50 to 60 percent. Larger calibers sharply increased loading time and the machinery required to move shells and charges. Quad mounts compounded shock, barrel-strength, and reliability problems. A navy might therefore return to more numerous 15- or 16-inch guns unless rivals forced continued escalation.