The ships had a stowage capacity of of coal and of oil, giving them a range of at a speed of . The battlecruisers were designed to reach a speed of and all of them exceeded that speed on their sea trials. The Kongō and Hiei attained and with and , respectively. In their first reconstruction during the late 1920s, the ships were reboilered with 10, 11 (Hiei) or 16 (Haruna) Kampon boilers, and their fuel stowage was rearranged to accommodate of coal and of oil. This increased their range to at 14 knots and allowed the fore funnel to be removed, which greatly decreased smoke interference with the bridge and fire-control systems. Coupled with the addition of external torpedo bulges, this reduced their speed to and caused the IJN to reclassify them as battleships. During their 1930s reconstructions into fast battleships, the existing boilers were removed and replaced with eleven oil-fired Kampon boilers. These upgraded boilers gave the Kongō and her sister ships much greater power, with the ships of the class capable of speeds exceeding . This made them the only Japanese battleships at the time fully suited to operations alongside fast aircraft carriers. Armament The primary armament of the Kongō class consisted of eight 14"/45 guns, mounted in four superfiring twin-gun turrets. The turrets had an elevation capability of −5/+20 degrees, except in Kongō, whose turrets had a maximum elevation capability of +25 degrees. The shells could be loaded at any angle and the guns had a firing cycle of 30–40 seconds. These guns and their turrets underwent multiple modernizations throughout the ships' careers. During the first reconstruction of the class during the 1920s, the elevation of the main guns was increased to a maximum of +33 degrees. The recoil mechanism of the guns was also changed from a hydraulic to pneumatic system, which allowed for a faster firing cycle of the main guns. By World War II, the guns used Type 91 armor-piercing, capped shells. Each of these shells weighed and had a muzzle velocity of . They had a maximum range of at +20 degrees of elevation and at +33 degrees after modernisation. Also available was a high-explosive shell that had a muzzle velocity of . A special Type 3 Sanshikidan incendiary shrapnel shell was developed in the 1930s for anti-aircraft use. As built, the Kongō class was fitted with a secondary armament of sixteen