Projectile weight, range, and the price of development

How did the four-inch, 4.5-inch, 4.7-inch, and 5.25-inch rounds compare?

The relevant 4.5- and 4.7-inch projectiles were close enough in weight that funding, shell design, muzzle velocity, and mounting elevation mattered more than a nominal five-pound difference.

Published 4.7-inch figures vary, partly because projectile weight and complete-round weight are different measures. The 5.25-inch projectile was substantially heavier for manual handling, while the 4.5- and 4.7-inch projectiles differed by only about five pounds. The Royal Navy invested in a new 4.5-inch shell and mounting, and equivalent work on 4.7-inch ballistics could have improved range and high-angle performance. The decisive requirement remains an 80-degree mounting rather than a marginal calibre or weight advantage.