page_title: Japanese battleship Mutsu
section_title: Armament
hierarchical_section_title: Japanese battleship Mutsu / Description / Armament
caption_attribution_description: English: A twin-127mm dual purpose gun mount on board the Japanese battleship Nagato
context_page_description: Mutsu was the second and last Nagato-class dreadnought battleship built for the Imperial Japanese Navy at the end of World War I. It was named after the province. In 1923 she carried supplies for the survivors of the Great Kantō earthquake. The ship was modernized in 1934–1936 with improvements to her armour and machinery, and a rebuilt superstructure in the pagoda mast style.
  Other than participating in the Battle of Midway and the Battle of the Eastern Solomons in 1942, where she did not see any significant combat, Mutsu spent most of the first year of the Pacific War in training. She returned to Japan in early 1943. That June, one of her aft magazines detonated while she was at anchor, sinking the ship with the loss of 1,121 crew and visitors. The IJN investigation into the cause of her loss concluded that it was the work of a disgruntled crew member. The navy dispersed the survivors in an attempt to conceal the sinking in the interest of morale in Japan. Much of the wreck was scrapped after the war, but some artefacts and relics are on display in Japan, and a small portion of the ship remains where it was sunk.
context_section_description: Mutsu's eight 45-calibre 41-centimetre (16.1 in) guns were mounted in two pairs of twin-gun, superfiring turrets fore and aft. Numbered one to four from front to rear, the hydraulically powered turrets gave the guns an elevation range of −2 to +35 degrees. The rate of fire for the guns was around two rounds per minute. A special Type 3 Sankaidan incendiary shrapnel shell was developed in the 1930s for anti-aircraft use. The turrets aboard the Nagato-class ships were replaced in the mid-1930s using those stored from the unfinished Tosa-class battleships. While in storage the turrets were modified to increase their range of elevation to −3 degrees to +43 degrees, which increased the guns' maximum range from 30,200 to 37,900 metres (33,000 to 41,400 yd).
  The ship's secondary armament of twenty 50-calibre 14-centimetre (5.5 in) guns was mounted in casemates on the upper sides of the hull and in the superstructure. The manually operated guns had a maximum range of 20,500 metres (22,400 yd) and fired at a rate of six to ten rounds per minute. Anti-aircraft defence was provided by four 40-calibre 8-centimetre (3 in) 3rd Year Type AA guns in single mounts. These guns had a maximum elevation of +75 degrees, and a rate of fire of 13 to 20 rounds per minute. The ship was also fitted with eight 533-millimetre (21 in) torpedo tubes, four on each broadside, two above water and two submerged.
  Around 1926, the four above-water torpedo tubes were removed and the ship received three additional 76 mm AA guns that were situated around the base of the foremast. The 76 mm AA guns were replaced by eight 40-calibre 12.7-centimetre (5 in) dual-purpose guns in 1932, fitted on both sides of the fore and aft superstructures in four twin-gun mounts. When firing at surface targets, the guns had a range of 14,700 metres (16,100 yd); they had a maximum ceiling of 9,440 metres (30,970 ft) at their maximum elevation of +90 degrees. Their maximum rate of fire was 14 rounds a minute, but their sustained rate of fire was around eight rounds per minute. Two twin-gun mounts for licence-built Vickers 2-pounder (40 mm (1.6 in)) "pom-pom" light AA guns were also added to the ship in 1932. These guns had a maximum elevation of +80 degrees, which gave them a ceiling of 4,000 metres (13,000 ft). They had a maximum rate of fire of 200 rounds per minute.
  The two-pounders were replaced by 1941 by 20 licence-built Hotchkiss 25 mm (1 in) Type 96 light AA guns in five twin-gun mounts. This was the standard Japanese light AA gun during World War II, but it suffered from severe design shortcomings that rendered it a largely ineffective weapon. According to historian Mark Stille, the twin and triple mounts "lacked sufficient speed in train or elevation; the gun sights were unable to handle fast targets; the gun exhibited excessive vibration; the magazine was too small, and, finally, the gun produced excessive muzzle blast". These 25-millimetre (0.98 in) guns had an effective range of 1,500–3,000 metres (1,600–3,300 yd), and an effective ceiling of 5,500 metres (18,000 ft) at an elevation of 85 degrees. The maximum effective rate of fire was only between 110 and 120 rounds per minute because of the frequent need to change the 15-round magazines.
caption: A twin 127 mm gun mount aboard Nagato
exif: {"Thumbnail JPEGInterchangeFormat": "44", "Thumbnail JPEGInterchangeFormatLength": "8338"}