The logistics benefit of standardizing on five-inch ammunition

Why did the US Navy retain five-inch guns in several barrel lengths instead of adopting many medium calibres?

Standard calibre delivered logistical commonality even when individual five-inch weapons used different barrel lengths and performance profiles.

Retaining five-inch guns in 25-, 38-, and 54-calibre lengths preserved a common bore across weapons with different performance. The immediate benefit emphasized here is ammunition logistics. The Bureau of Ordnance's attachment to the calibre is treated as producing a useful supply outcome, whatever its institutional motives. The comparison concerns standardization across a weapon family, without establishing that every complete round was interchangeable.