The Weymouth batch answered concerns that the 4-inch weapon lacked punch by carrying eight BL 6-inch Mark XI guns. Each gun weighed almost 8.75 tons and fired a 100-pound shell at about 2,900 feet per second to a maximum range of 18,000 yards. Later ships preferred a lighter 45-calibre weapon that crews could handle more easily. The Weymouths also moved from 18-inch to 21-inch torpedoes, giving their underwater battery a heavier blow against larger opponents. By the Second World War, 18,000 yards was often treated as a practical engagement distance for visual fire control before dependable radar.
Notable Point · 6:21-9:32
Why the Weymouths adopted an all-6-inch battery
The second Town-class batch replaced the mixed battery with eight long 6-inch guns and enlarged its torpedoes from 18 to 21 inches.