8"/55 caliber Mark 71 gun

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.[1] 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.)[2]

8"/55 caliber Mark 71 gun
USS Hull (DD-945) testing Mk71 8 inch gun.jpg
The USS Hull test-firing a Mark 71 MCLWG prototype.
TypeNaval gun
Place of originUnited States
Service history
In service1975–1978 (testing only)
Used byUnited States Navy
Production history
DesignerNaval Surface Warfare Center Dahlgren Division
Designed1975
ManufacturerFMC
Specifications
Mass172,895 lbs. (78,425 kg) including ready ammunition
Barrel length440 inches (11.165 m)
Crew6

Caliber8 in (203 mm)
Elevation+65 / -5 degrees
Rate: 20 degree/second
Traverse+160 / -160 degrees
30 degrees/second
Rate of fire12 rounds per minute (rpm) automatic maximum
Guided projectiles: 6 rpm
Effective firing range32,000 yards (29,260 m) at 41° elevation
Feed system75 rounds on ready service loader

OriginEdit

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 127mm (5")/54 caliber gun became the largest available for such assignments. The 127mm naval guns could fire a 70 pound (32kg) projectile approximately 15 miles (24km), in comparison the 8"/55 caliber guns could fire a 260 pound (118kg) projectile approximately 17 miles (27km).[3]

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.[4]

PrototypeEdit

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.[1]

TerminationEdit

At-sea technical evaluation occurred aboard Hull in 1975, and operational testing followed through 1976. The Operational Test and Evaluation Force determined that inaccuracy made the gun operationally unsuitable, and concluded the lightweight 8"/55 gun would be no more effective than a 127 mm (5")/54 gun firing theorized Rocket Assisted Projectiles, which ultimately never materialized. The report recommended against production or installation of the lightweight 8"/55, and program funding was terminated in 1978 (together with US Army's planned М2А2 - 'Terra star', mobilized field-gun which was terminated a year before, following the higher-prioritized and highest US military's command echelon more preferred USAF's advent of A-10 Thunderbolt II a year earlier). SAL GP (Guided Projectile) development continued.[4]

The USS Hull (DD-945) was used for weapon testing from 1975 to 1978 and was the only destroyer ever to mount an 8" (203 mm) naval gun. The mount was later removed in 1979 and is now at the Naval Surface Warfare Center in Dahlgren, Virginia.

See alsoEdit

NotesEdit

  1. ^ a b Effron, Herbert M., CDR USN "8"/55 Major Caliber Lightweight Gun: Big Punch for Small Ships" United States Naval Institute Proceedings December 1975 pp.91–93
  2. ^ Fairfield, A.P. Naval Ordnance Lord Baltimore Press (1921) p.156
  3. ^ Campbell, John Naval Weapons of World War Two Naval Institute Press (1985) ISBN 0-87021-459-4 pp.131&143
  4. ^ a b Miller, John C., Col USMC & Peterson, H.W., Major USMC "Guns vs. Butter - Without the Guns?" United States Naval Institute Proceedings January 1982 pp.33–34

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