8 inch/55 Mark 9 (203 mm)

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8 inch/55 Mark 9 cannons on the USS Northampton


Write an introduction to the article in 2-3 small paragraphs. Briefly tell us about the history of the development and combat using the weaponry and also about its features. Compile a list of air, ground, or naval vehicles that feature this weapon system in the game.

Vehicles equipped with this weapon

General info

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Available ammunition

Penetration statistics
Ammunition Type of
Penetration @ 0° Angle of Attack (mm)
1,000 m 2,500 m 5,000 m 7,500 m 10,000 m 15,000 m
Mk.14 Common Common 116 102 83 69 57 43
Mk.19 APCBC APCBC 383 339 277 228 190 143
Mk.25 HC HE 61 61 61 61 61 61
Mk.17 SP Common SP Common 137 121 99 81 68 51
Shell details
Ammunition Type of
mass (kg)
Fuse delay
Fuse sensitivity
Explosive mass
(TNT equivalent) (kg)
0% 50% 100%
Mk.14 Common Common 853 117.9 0.035 9 4.84 47° 60° 65°
Mk.19 APCBC APCBC 853 117.9 0.035 9 1.62 48° 63° 71°
Mk.25 HC HE 853 117.9 0 0.1 9.49 79° 80° 81°
Mk.17 SP Common SP Common 853 117.9 0.035 9 4.61 48° 63° 71°

Comparison with analogues

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Usage in battles

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Pros and cons

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After World War I, the victorious parties of the Entente Powers came to together to sign an agreement that would prevent another naval arms race like the dreadnought arms race that had preceded the Great War. As part of the negotiations, it was decided to divide cruisers between light and heavy cruisers based on the calibre of their guns. Heavy cruisers were defined as armed with 8 inch guns and a displacement of 10,000 tons, chosen to appease the British, American, and Japanese signatories who were all planning on cruisers with this calibre of guns. For the United States, their standard heavy cruiser armament became the 8 inch, fifty-five calibre guns, a built-up gun design that entered service in 1925. Weighing about 30 tons including a liner, tube, jacket, and five hoops, these guns had a down-swing Welin breech block closed by compressed air from the gas ejector system. The first ships built to mount these guns were the Lexington-class battlecruisers which had 4 twin gun turrets with the Mark 9 guns. However, the Washington Naval Treaty restrictions on constructing these types of ships led to their conversion to aircraft carriers and the cannons were repurposed as coastal defense guns on the Hawaiian Island of Oahu. Later in 1926, USS Pensacola and its sister ship Salt Lake City featured both two twin turrets and two triple turrets with the Mark 9. The following year, the Northampton and its class was built with 3 triple turrets with Mark 9 guns. In 1930, Portland and Indianapolis were built with 3 triple-turreted Mark 9s, and in 1931, the guns were fitted on the early New Orleans-class ships, the New Orleans, Minneapolis, and Astoria, before being replaced by the lighter 8 inch/55 Mark 12. The earlier ships armed with the Mark 9 would be refitted later in the war for the similar but superior 8 inch/55 Mark 14, except for Chicago, Houston, and Astoria which were sunk during the war, and Minneapolis which received the improved Mark 15 gun.


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See also

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External links

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USA naval cannons
20 mm  20 mm/70 Oerlikon Mk.II · 20 mm/70 Oerlikon Mark V · 20 mm/70 Oerlikon Mark 24
25 mm  25 mm/87 Mk.38
28 mm  1.1 inch/75 Mk.1
37 mm  AN-M4
40 mm  Bofors L/60 Mark 1 · Bofors L/60 Mark 2 · Bofors L/60 Mark 3
76 mm  3 inch/23 Mk.4 · 3-inch/50 Mk.10 · 3-inch/70 Mk.37 · 3-inch Mark 10 · 3 inch Mk.33 · 3-inch Mk.34
102 mm  4 inch/50 Mk.9
127 mm  5 inch/25 Mk.11 · 5 inch/25 Mk.13 AA · 5 inch/38 Mk.12 · 5-inch/50 Mk.5 · 5 inch/51 Mk.7 · 127 mm/54 Mark 18
152 mm  6 inch/47 Mk.16 · 6 inch/47 DP Mk.16 · 6 inch/53 Mk.12 · M81
203 mm  8 inch/55 Mark 9 · 8 inch/55 Mark 12 · 8 inch/55 Mark 14 · 8 inch/55 Mark 16
305 mm  12-inch/45 Mk.5 · 12 inch/50 Mk.7 · 12 inch/50 Mk.8
356 mm  14 inch/45 Mk.8 · 14 inch/45 Mk.12 · 14 inch/50 Mk.11