| Is Artillery: | yes |
| Is Explosive: | yes |
| Is Ranged: | yes |
| 12"/50 caliber Mark 8 gun | |
| Origin: | United States |
| Used By: | s |
| Wars: | World War II |
| Type: | Naval gun |
| Design Date: | 1939 |
| Manufacturer: | Naval Gun Factory, Midvale and Bethlehem Steel Corporation, Watervliet Arsenal |
| Service: | 1944 - 1961[1] |
| Caliber: | 12inches |
| Part Length: | 51feet bore (50 cal) |
| Rate: | 2.4 - 3.0 rounds per minute |
| Cartridge: | 1140lb |
| Max Range: | 38573yd |
The 12"/50 caliber gun Mark 8 was a US naval gun mounted on the . The gun, like the "large cruiser" that mounted it, was intended to fill the gap between US "heavy cruisers" (6-8") and US battleships (14-16"). The name describes the size of the shells, 12 inches in diameter, and the length of the bore in calibers (50 bore diameters).
The gun was designed in 1939, and a prototype was tested in 1942. Unlike previous guns, such as the 16"/45 caliber guns used on the, which were completely made and assembled at the Naval Gun Factory in Washington D.C., the forgings for the Mark 8 were manufactured at the Midvale and Bethlehem Steel corporations. They were then sent to the Naval Gun Factory for processing, which was followed by a trip to Watervliet Arsenal until they were 65% complete. Finally, the built-up guns were sent back to the Naval Gun Factory to be finished.
The gun was first deployed in 1944, on the lead ship of the Alaska class, .[2] The two Alaska-class ships each had nine Mark 8 guns mounted in three triple (3-gun) turrets, with two turrets forward and one aft, a configuration known as "2-A-1". Only two vessels of the class were completed, making them the only applications of the Mark 8 12"/50 caliber gun.
The Mark 8 weighed 121856lb including the breech and was capable of an average rate of fire of 2.4 - 3 rounds a minute. It could throw a 1,140 lb. (517.093 kg) Mark 18 armor-piercing shell 38,573 yards (35,271 meters) at an elevation of 45°.[2] [3] The previous 12" gun manufactured for the U.S. Navy was the Mark 7 version, used in the World War I era s,[2] could only throw an 870sp=usNaNsp=us shell 24000yard, at an elevation of 15°[4] The Mark 8's significant improvement in firing weight and range over the Mark 7 gave it the honor of "by far the most powerful weapon of its caliber ever placed in service."[5] In fact, as a result of the decision to fire "super heavy" armor-piercing projectiles, the Mark 8's deck plate penetration was better and the side belt armor penetration equal to the older (but larger) 14"/50 caliber gun.
The barrel life of the Mark 8 guns was 344 rounds, 54 more than the 16"/50 caliber Mark 7 gun found in the s.[2] [3]