The limits of Phalanx as close-in defence

Should modern warships retain the 20 mm Phalanx, or move toward a heavier close-in gun?

Keep the close-in gun concept, but reconsider the 20 mm weapon and magazine; a 30 or 40 mm successor could offer more range, ammunition effects and staying power within a layered defence.

Phalanx remains a sound close-in weapon concept, but its 20 mm Vulcan and external ammunition drum limit range and staying power. A heavier 30 or 40 mm gun could use programmable ammunition and throw a destructive pattern farther from the ship, although the engineering would be difficult. The continued growth of warship displacement weakens the claim that there is never room for a larger mount or magazine. Missiles add another layer, yet their ready rounds are limited and reloading at sea is slow. A gun also remains useful against small craft in confined waters such as canals. These constraints favour overlapping defences and raise the question of whether a fourth generation of Phalanx-carrying ships should retain the original calibre.