Barrel length, elevation, and turret balance pull in different directions

Why did the Royal Navy retain 42-calibre heavy guns when other navies adopted longer barrels?

Longer barrels offered more velocity and range, but demanded heavier, carefully balanced high-elevation turrets, while Britain had not funded a complete replacement gun programme.

Longer barrels can raise muzzle velocity and range, but they also put more weight forward of a turret's pivot. A mounting designed for high elevation must counterbalance that mass while preserving reliable training and loading. Designers therefore choose among direct-fire power, plunging trajectories, range, mechanical complexity, and available investment rather than simply selecting the longest possible weapon. The British reliance on older 42-calibre guns is presented partly as inherited First World War practice and partly as a consequence of limited interwar gun development.