distance of . The gun's rate of fire was approximately 96–98 rounds per minute. Like previous classes of British battleships, a pair of submerged, broadside-firing torpedo tubes were planned for these ships. Their compartment was located just forward of the 'A' shell room on the platform deck. Six torpedoes per tube were to be carried in peace-time, but this would increase to eight in wartime. These Mark I torpedoes had a warhead of of TNT and were powered by oxygen-enriched air. They had two speed settings which governed their range: either at , or at . Fire-control The main guns of the battleships could be controlled from either of the two director-control towers (DCT). The primary DCT was mounted at the top of the forward superstructure. Another was mounted on the roof of the conning tower in an armoured hood. Each main gun turret was provided with a coincidence rangefinder in an armoured housing on the turret roof. The secondary armament was primarily controlled by two DCTs mounted on each side of the bridge. The anti-aircraft guns were controlled by a high-angle control system mounted on the mizzenmast. Each pom-pom mount had its own director and there was also a height-finder aft. Two torpedo rangefinders were located on the sides of the funnels. Armour A first for any British dreadnought was the use of the all or nothing protection scheme in the N3s and G3s. Medium-thickness armour had proven to be useless in stopping heavy-calibre shells during World War I so the vital areas of the ship were protected by the thickest possible armour and the rest of the ship was left unarmoured. Use of this system was pioneered by contemporary U.S. Navy battleship designs starting with the . This system of protection required that the armoured citadel have enough reserve buoyancy to keep the ship stable even if the rest of the hull was riddled by gunfire. The waterline belt of the N3 had a maximum thickness of thick with the top of the armour angled outward at 25°. This angle increased the armor's relative thickness to horizontal, close-range fire, albeit at the cost of reducing its relative height which increased the chance of plunging shellfire going over or under it. It ran some , from forward of 'A' barbette to the rear of the after 6-inch magazine. For about , it reduced to over the engine and boiler