Why six twin 5-inch mounts do not fit a destroyer

If earlier US destroyers carried four or five twin mounts, should Somers-class successors receive as many as six twin 5-inch/38 mounts?

No. The deck-space, machinery, torpedo, topweight, and hull-form penalties make about three twin mounts far more realistic.

The proposed battery requires surrendering torpedo launchers simply to find enough deck space. Haida's machinery spaces illustrate how tightly engines already fill a large destroyer from keel toward the upper deck. Lengthening the hull while keeping it narrow enough for treaty displacement would reproduce the structural and seakeeping problems associated with some French and Italian designs. Three twin mounts are a much more credible upper limit for a destroyer that still has to perform its other missions. The exchange shows why a paper gun count cannot be separated from machinery volume, topweight, and hull proportions.