Figured i'd answer the question seeing as I came looking for the answer then remembered i'd tested it out ^^ haha
The 5"/38 Mark 12 is the best. The ones that look like the US 5" guns everyone uses for AA.
The duals GA is something reasonable like 31 or thereabouts, but the singles are better at around 25 or thereabouts. Test it yourself to be sure. But make sure you have ridiculous reload on your gunners, BVE as much as you can manage, and maybe use gradual too.
However it is just about useable I found. It's no KM or IJN, but maybe another UK style lol. You can't spam AA effectively, but if you aim well you can one shot pretty much anything.
