Originally the intended gun armament was two twin Second World War standard mounts, then scheduled for a twin 70 caliber, mount but that and the required magazine, increased weight by 256 tons and then designed a gun fit of two single automatic 4-inch guns which required a hull 10 ft longer but were like the twin 3/70s too expensive and resulted in a 3000-ton displacement unacceptable for a sloop or even frigate design for the RN/Treasury in the 1960s of the sort fitted to the Chilean "Almirante Williams" class.