8"/55 caliber Mark 71 gun
|8"/55 caliber Mark 71 gun|
The USS Hull test-firing a Mark 71 MCLWG prototype.
|Place of origin||United States|
|In service||Never used|
|Used by||United States Navy|
|Designer||Naval Surface Warfare Center Dahlgren Division|
|Weight||172,895 lbs. (78,425 kg) including ready ammunition|
|Barrel length||440 inches (11.165 m)|
|Caliber||8 in (203 mm)|
|Elevation||+65 / -5 degrees
Rate: 20 degree/second
|Traverse||+160 / -160 degrees
|Rate of fire||12 rounds per minute (rpm) automatic maximum
Guided projectiles: 6 rpm
|Effective firing range||32,000 yards (29,260 m) at 41° elevation|
|Feed system||75 rounds on ready service loader|
The U.S. Navy's Major Caliber Lightweight Gun (MCLWG) program was the 8"/55 caliber Mark 71 major caliber lightweight, single-barrel naval gun prototype (spoken "eight-inch-fifty-five-caliber") that was mounted aboard the USS Hull (DD-945) in 1975 to test the capability of destroyer-sized ships to replace decommissioned cruisers for long-range shore bombardment. United States naval gun terminology indicates the gun fired a projectile 8 inches (203 mm) in diameter, and the barrel was 55 calibers long (barrel length is 8" × 55 = 440" or 11.165 meters.)
Gunfire support from cruisers and battleships had become an established part of United States amphibious warfare doctrine during World War II. As the last of the wartime cruisers and battleships were decommissioned, the 5"/54 caliber gun became the largest available for such assignments. The 5"/54 could fire a 70-pound (32-kg) projectile approximately 15 miles (24 km) in comparison to a range of 17 miles (27 km) for 260 pound (118 kg) projectiles from the 8"/55 caliber guns of heavy cruisers.
The impending loss of capability was anticipated by the Chief of Naval Operations (CNO) in 1969. CNO established a requirement for a new gun capable of firing semi-active laser guided projectiles (SAL GP). Development took place through 1971 and 1972 at the Naval Surface Warfare Center Dahlgren Division.
The 8"/55 Mark 71 gun was a single gun adaptation of the 8"/55 Mark 16 gun found in triple turrets on Des Moines class cruisers. The prototype gun mount weighed 86 tons and was approximately 20 percent heavier than the 5"/54 caliber Mark 42 gun it replaced. The prototype could fire ten to twelve rounds per minute from a 75-round automatic ready service magazine for semi-fixed ammunition when operated by one man. A specially modified Mark 155 ballistic computer provided 8"/55 ballistics for Hull's Mark 68 gun fire control system.
At-sea technical evaluation occurred aboard Hull in 1975, and operational testing followed through 1976. The Operational Test and Evaluation Force determined inaccuracy made the gun operationally unsuitable, and concluded the lightweight 8"/55 was no more effective than the 5"/54 (with Rocket Assisted Projectiles). The report recommended against production or installation of the lightweight 8"/55, and program funding was terminated in 1978. SAL GP development continued.
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