Would a 12,000-ton, 9.2-inch cruiser category bring the fast-firing 6-inch gun into service earlier or later?
Short answerProbably at about the same time, because the decisive factor is the pace of gun technology rather than the displacement available to the ship.
NotesA treaty can change which hull receives a weapon without instantly changing the weapon's engineering maturity. Loading arrangements, mount design, ammunition handling, and manufacturing must still develop. Larger cruisers might alter the demand signal or the classes in which the gun appears. The broad technological timeline nevertheless remains unchanged because the counterfactual does not directly accelerate those underlying systems.