Would a 15-inch/50 weapon have spread across the Royal Navy?

If the 15-inch/50 had entered service with F2 or F3, would the Royal Navy have regunned much of its existing capital-ship fleet?

More than likely; adopting the new weapon would have created a strong operational and logistical case for extending it to older 15-inch ships and later battleship designs.

F2 and F3 were the likely entry point for a new 15-inch/50 rather than a one-class experiment. The weapon could then have moved into rebuilt 15-inch ships and shaped the armament of later battleships. A common calibre would preserve the familiar shell diameter while offering substantially greater barrel length and performance. The viewer's question turns that counterfactual into a fleet-level consequence: once the weapon and its supply system existed, refitting compatible ships would become much more attractive. The result could have been a more uniform British heavy-gun inventory than the later mix of 14-, 15-, and 16-inch weapons.