Early autoloading six-inch dual-purpose guns

Would the Tiger-class autoloading six-inch gun have gone onto Vanguard if available earlier?

Probably, but the larger effect would be new cruiser classes armed with autoloading six- and three-inch weapons for Pacific air defense.

The premise depends on the weapons becoming reliable and fully worked up early enough for wartime production. Vanguard could receive the autoloading armament, but the larger effect would appear in whole batches of new cruisers. Six-inch guns capable of useful anti-aircraft fire, paired with early automatic three-inch weapons, would make those cruisers especially desirable for the Pacific Fleet. The counterfactual changes fleet-wide air defence and cruiser construction, with Vanguard as one part of the program.