砲口初速
The "King Edward VII"s had four 12-inch 40-calibre Mk IX guns mounted in twin-gun turrets fore and aft. The guns were carried in BVIIS-type mountings, which had a range of elevation from -5 degrees to of 13.5 degrees, and required the guns to return to 4.5 degrees to be loaded. The guns had a muzzle velocity of , and they were capable of penetrating 12 inches of Krupp armour at a range of . At their maximum elevation, the guns had a range of . "Commonwealth" and "Zealandia" later had their mounts modified to allow elevation to 30 degrees, which extended their maximum range significantly, to . These were supported by a heavy secondary battery of four guns in four single turrets, two on each broadside. The guns were carried in Mk VS mounts, which had a range of elevation from -7 to +15 degrees, allowing for a maximum range of . Muzzle velocity was .