The British repeatedly thought of building a 5in gun for destroyers and secondary armaments

Prior to the First World War, and even during the war, the British had hoped to build a 5in gun for use on capital ships and destroyers. They had such a caliber in the 1880's, for use on their scout cruisers. In the run up to the war, building the 15in gun was higher priority, so it was never built. There were persistant stories that a 5in gun was under development, but it never was actually constructed. In the end, a commercial 4.7in gun was available, so that was used instead. Meanwhile, the Americans adopted the 5in gun, and eventually, so did the Japanese. In the 1930's, the British revisited destroyer guns and guns for secondary armaments on capital ships. At one point, a 13cm gun (5.1in) was seriously considered. The Germans and French were using such guns, so there was some reason to consider adopting it. For capital ships, the British initially went with the totally inadequate 5.25in DP gun. The 5.25in gun was barely DP, as the elevation was marginal and the shell too heavy. They turned to the 4.5in DP gun for capital ship modernization. The Renown, Queen Elizabeth, and Valiant received them. By the time the Battle class destroyers were designed, the 4.5in gun seemed like the best choice. Apparently one reason that the British never developed a 5in gun was that they were concerned about the shell weight. Their experience in World War One was that large guns were inappropriate for small ships, as they had difficulty in manhandling large shells in a seaway.