Britain already had the production and support infrastructure needed for its 13.5-inch guns. Moving to 14 inches would have required expensive industrial changes to supply the navy at the necessary scale. The comparison returns to the American choice between an established 16-inch weapon and a theoretical 16.5-inch alternative. Small calibre differences can matter in some circumstances, but the judgment here is that these particular half-inch increases offered too little benefit to justify rebuilding the supporting system.
Notable Point · 38:51-39:37
Why half an inch could fail to justify a new gun industry
Established gun-production infrastructure could outweigh the limited gain from moving British 13.5-inch guns to 14 inches or American 16-inch guns to 16.5 inches.