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Naval gun From Wikipedia, the free encyclopedia
The 12"/50 caliber gun Mark 8 was a US naval gun mounted on the Alaska-class cruiser. 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).
| 12"/50 caliber Mark 8 gun | |
|---|---|
_firing_main_battery,_1944-45.jpg) USS Guam firing her 12"/50 guns during a training session sometime in 1944–1945. | |
| Type | Naval gun |
| Place of origin | United States |
| Service history | |
| In service | 1944–1961[1][2] |
| Used by | Alaska-class cruisers |
| Wars | World War II |
| Production history | |
| Designed | 1939 |
| Manufacturer | Naval Gun Factory, Midvale and Bethlehem Steel Corporation, Watervliet Arsenal[1] |
| Specifications | |
| Barrel length | 51 feet (15.54 m) bore (50 cal)[1] |
| Shell | 1,140 pounds (520 kg) |
| Caliber | 12 inches (304.8 mm)[1] |
| Rate of fire | 2.4–3.0 rounds per minute[1] |
| Maximum firing range | 38,573 yards (35,271 m)[1] |
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 North Carolina class, 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, USS Alaska.[1] 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 121,856 pounds (55,273 kg) 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°.[1][3] The previous 12" gun manufactured for the U.S. Navy was the Mark 7 version, used in the World War I era Wyoming-class battleships,[1] could only throw an 870-pound (390 kg) shell 24,000 yards (21,946 m), 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 Iowa-class battleships.[1][3]
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