The 50 calibre BL 8 inch gun Mark VIII[note 1] was the main battery gun used on the Royal Navy's County-class heavy cruisers,[note 2] in compliance with the Washington Naval Treaty of 1922. This treaty allowed ships of not more than 10,000 tons standard displacement and with guns no larger than 8 inches (203 mm) to be excluded from total tonnage limitations on a nation's capital ships. The 10,000 ton limit was a major factor in design decisions such as turrets and gun mountings. A similar gun formed the main battery of Spanish Canarias-class cruisers. In 1930, the Royal Navy adopted the BL 6 inch Mk XXIII naval gun as the standard cruiser main battery in preference to this 8-inch gun.
|Ordnance BL 8 inch gun Mk VIII|
Forward 8-inch turrets aboard HMAS Canberra
Coast defence gun
|Place of origin||United Kingdom|
|In service||1927 – 1954|
|Used by||Royal Navy |
Royal Australian Navy
|Wars||Second World War|
|Barrel length||400 inches/10 meters(50 calibres)|
|Shell||256 pounds (116 kg)|
|Calibre||8-inch (203 mm)|
|Muzzle velocity||2805 feet per second (855 m/s)|
|Maximum firing range||28 kilometres (17 mi)|
These built-up guns consisted of a wire-wound tube encased within a second tube and jacket with a Welin breech block and hydraulic or hand-operated Asbury mechanism. Two cloth bags each containing 15 kg (33 lb) of cordite were used to fire a 116 kg (256 lb) projectile. Mark I turrets allowed gun elevation to 70 degrees to fire high-explosive shells against aircraft. Hydraulic pumps proved incapable of providing sufficient train and elevation speed to follow contemporary aircraft; so simplified Mark II turrets with a maximum elevation of 50 degrees were installed in the Norfolk subgroup ships Dorsetshire and Norfolk and the York-class cruisers York and Exeter. Each gun could fire approximately five rounds per minute. Useful life expectancy was 550 effective full charges (EFC) per barrel.
The following ships mounted Mk VIII guns in 188-tonne twin turrets. The standard main battery was four turrets, but Exeter and York carried only three to reduce weight and formed the separate York class.
|Range||Elevation||Time of flight||Descent||Impact velocity|
|5000 yd (4.6 km)||2° 11′||6 s||2° 31′||2154 ft/s (657 m/s)|
|10000 yd (9.1 km)||5° 14′||14 s||7° 15′||1683 ft/s (513 m/s)|
|15000 yd (14 km)||9° 47′||25 s||15° 49′||1322 ft/s (403 m/s)|
|20000 yd (18 km)||16° 34′||38 s||28° 31′||1169 ft/s (356 m/s)|
|25000 yd (23 km)||26° 44′||56 s||43° 7′||1164 ft/s (355 m/s)|
|29000 yd (27 km)||41° 28′||79 s||56° 37′||1240 ft/s (378 m/s)|
The 20.3 cm SK C/34 was the main battery gun used on the German Admiral Hipper-class heavy cruisers.203 mm/53 Italian naval gun
The 203 mm/53 Ansaldo was the main battery gun of Italy's most modern Washington Naval Treaty heavy cruisers. This treaty allowed ships of not more than 10,000 tons standard displacement, and with guns no larger than 8 inches (203 mm), to be excluded from total tonnage limitations on a nation's capital ships.203mm/50 Modèle 1924 gun
The 203mm/50 Modèle 1924 was a medium naval gun of the French Navy.
The type was used on the Duquesne and Suffren classes of heavy cruisers as main battery, mounted in four twin turrets weighing 180 tonnes each. The calibre of 203 mm (8 inches) was characteristic of heavy cruisers built as a result of limitations imposed by the Washington Naval Treaty of 1922.20 cm/50 3rd Year Type naval gun
Third year type 20 cm/50 caliber guns (五十口径三年式二〇糎砲, gojūkōkei sannenshiki ni-maru centi-hō) formed the main battery of Japan's World War II heavy cruisers. These guns were also mounted on two early aircraft carriers. The typical installation was ten 20 cm/50 guns; although Tone-class cruisers carried eight while Furutaka and Aoba-class cruisers carried six. After modernization, Akagi carried only six.
These were built-up guns with an inner A tube, encased by a second tube, encased by a full length jacket. Early guns were partially wire-wound, but later guns dispensed with the wire winding. The guns were breech loaded with two cloth bags of smokeless powder. Third year type refers to the Welin breech block on this gun. Breech block design began in 1914 AD, the third year of the Taishō period. This breech block design was also used on Japanese 41 cm (16.1 inch), 15.5 cm (6 inch), 14 cm (5.5 inch), 12.7 cm (5 inch), and 12 cm (4.7 inch) naval guns.8"/55 caliber gun
The 8"/55 caliber gun (spoken "eight-inch-fifty-five-caliber") formed the main battery of United States Navy heavy cruisers and two early aircraft carriers. United States naval gun terminology indicates the gun barrel had an internal diameter of 8 inches (203 mm), and the barrel was 55 calibers long (barrel length is 8 inch × 55 = 440 inches or 36.6 feet or 11 meters).BL 6-inch Mk XXIII naval gun
The 50 calibre BL 6 inch gun Mark XXIII was the main battery gun used on the Royal Navy and British Commonwealth's conventional (non-anti-aircraft) light cruisers built from 1930 through the Second World War, and passed into service with several other navies when ships were disposed of after the end of the War.BL 7.5-inch Mk VI naval gun
The BL 7.5-inch gun Mark VI was the 45 calibre naval gun forming the main battery of Royal Navy Hawkins-class cruisers. These ships with seven single gun mounts were significant to the cruiser limitations defined by the Washington Naval Treaty.Heavy cruiser
The heavy cruiser was a type of cruiser, a naval warship designed for long range and high speed, armed generally with naval guns of roughly 203 mm (8 inches) in caliber, whose design parameters were dictated by the Washington Naval Treaty of 1922 and the London Naval Treaty of 1930.
The heavy cruiser is part of a lineage of ship design from 1915 through the early 1950s, although the term "heavy cruiser" only came into formal use in 1930. The heavy cruiser's immediate precursors were the light cruiser designs of the 1900s and 1910s, rather than the armoured cruisers of before 1905. When the armoured cruiser was supplanted by the battlecruiser, an intermediate ship type between this and the light cruiser was found to be needed—one larger and more powerful than the light cruisers of a potential enemy but not as large and expensive as the battlecruiser so as to be built in sufficient numbers to protect merchant ships and serve in a number of combat theaters.
With their intended targets being other cruisers and smaller vessels, the role of the heavy cruiser differed fundamentally from that of the armored cruiser. Also, the heavy cruiser was designed to take advantage of advances in naval technology and design. Typically powered by oil-fired steam turbines rather than the reciprocating steam engines of the armoured cruiser, heavy cruisers were capable of far faster speeds and could cruise at high speed for much longer than could an armoured cruiser. They used uniform main guns, mounted in center-line superfiring turrets rather than casemates. Casemate guns and a mixed battery were eliminated to make room for above deck torpedoes, and ever increasing and more effective anti-aircraft armaments. They also benefited from the superior fire control of the 1920s and continually upgraded through the 1950s. Late in the development cycle radar and electronic countermeasure would also appear and rapidly gain in importance. These developments meant that the heavy cruiser was an overall more powerful ship type than the armoured cruiser had been.List of naval guns by caliber
List of naval guns of all countries, in increasing caliber size
|Capital ship main armament|
|Heavy cruiser main armament|
|Secondary armament and|
light cruiser main armament
|Minesweeper, Sloop, Corvette,|
Frigate and Destroyer armament
|Small craft armament|
|Field guns and howitzers|
|Medium and heavy |
guns and howitzers