A treaty maximum of 10 inches would tempt American and Japanese designers to use the largest permitted calibre. In this design comparison, 9.2-inch guns sit at the upper end of cruiser-grade turret machinery, while 10-inch shells demand heavier, capital-ship-style equipment. Britain could retain 9.2-inch guns to use its limited displacement more efficiently. A further Japanese possibility builds in the machinery needed for later 12-inch guns, but this would favour a six-gun arrangement because an eight-gun ship would be difficult to fit honestly within the limit.
Notable Point · 2:10:51-2:11:55
Why a 10-inch treaty maximum could favour 9.2-inch guns
Larger shells demand heavier turret machinery, potentially making 9.2-inch guns a better fit for a cruiser tonnage limit than the permitted 10-inch maximum.