Would a 5-inch gun refit make sense for the Type 45?

Could the Type 45 destroyers eventually receive a 5-inch gun refit?

Possibly, but ammunition commonality is the main case for it; adapting useful rounds to the existing 4.5-inch system may cost less than replacing the mount, handling equipment, and magazine.

A 5-inch refit would make most sense if Type 45 destroyers became the last ships using 4.5-inch ammunition and the navy wanted a common supply. Prospective 5-inch anti-submarine rounds add another argument because they could engage farther out than ship-launched torpedoes. Their potential value as a final layer of protection for a nearby carrier is weighed against the destroyer's primary air-defence role. BAE Systems is expected to be able to adapt the relevant projectiles to 4.5 inches. Developing those rounds for the existing gun is judged cheaper than replacing its mounting, handling equipment, and ammunition storage.