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Mark 71 8"/55 (203 mm) Major Caliber Lightweight Gun [MCLWG]

The Major Caliber Lightweight Gun ("MCLWG") was the result of a project dating back to the 1960s, when it was realized that heavy gunfire support for amphibious operations would die with the existing force of heavy cruisers unless a big gun could be developed for destroyer-size ships. A prototype gun and mounting had been built and tested ashore during the early 1970s.

The role of naval guns in World War II amphibious operations stemmed from the defensive strategy of Italian, German, and Japanese opponents. Their strategy, in turn, was dictated by the geographical characteristics of amphibious objectives and their inventory of military forces.

In the Mediterranean theater, large land masses and numerous potential landing beaches at Sicily and Italy limited the organization of beach defenses and coastal artillery positions and forced the Axis to depend on prompt counterattack with infantry and armored reserves against Allied landings. Consequently, the major contribution of naval guns was to assist in the disruption of these counterattacks, although guns were directed against the limited beach defenses and coastal artillery whenever the situation so required.

Japanese defensive strategy in the Central Pacific contrasted sharply. Amphibious objectives were far smaller, ranging in size from the tiny atolls in the Gilberts and Marshalls to the relatively large island of Okinawa, all characterized by relatively few potential landing sites. In all cases, Japanese military resources were sufficient for the organization of powerful beach defenses and coastal artillery positions. In this theater, the most important mission of the naval guns was the destruction of beach defenses and coastal artillery so that a foothold could be established without crippling casualties. However, field artillery, mortars, and rocket launchers were also taken under fire.

One of the major challenges to naval guns during World War II and Korea was the elimination of hostile coastal defense guns. These weapons played key roles in the defensive strategy of the Germans and the Japanese. In the Korean War, the North Koreans attempted to restrict the Navy's east-coast interdiction campaign by placing numerous coastal guns to command the sea approaches.

The last active Navy major-caliber-gun (8" or larger) warship, the heavy cruiser NEWPORT NEWS, was retired 27 June 1975. Future gunfire support would be essentially limited to the 5" guns carried by many remaining surface combatants. In Korea, where destroyers were forced to engage coastal batteries for their own protection during blockade operations and interdiction of rail lines, the 5-inch projectiles lacked lethality. Vietnam reconfirmed World War II and Korean experiences regarding projectile lethality; i.e., the 5"/54 projectile lacked the essential punch to -- defeat typical hard targets.

A new Major Caliber Lightweight Gun (MCLWG) development program had been underway for some time as a potential replacement for the large-caliber gunfire support previously provided by the cruisers and battleships. The relatively small bulk of this weapon would permit its installation in a variety of surface combatants.

The Major Caliber Lightweight Gun Mount (MCLGM) was a result of Navy and Marine Corps efforts beginning in 1960 to provide the fleet with the first major caliber gun mount to be designed since the end of World War II. This mount would provide firepower necessary to support troops ashore at ranges well beyond that of 5"0 guns and would provide greatly increased firepower for the fleet, particularly for smaller ships.

Initially a 175mm/60 caliber mount was specified because of the potential advantages of achieving commonality in ammunition with the Army 175mm gun. Northern Ordnance Division of FMC Corporation at Minneapolis (NOD/FMC) was awarded the contract to design and develop the mount. A prototype was fabricated and subjected to testing at NOD/fmc, including a 50.000 cycle life and reliability test, on the loading system. The mount was disassembled and delivered to the Naval Weapons Laboratory, Dahlgren. Virginia in August 1970 where it was reassemble checked, proof-fired and evaluated to verify that contract requirements were met.

The Army, however, developed only one type of projectile for an anticipated family of ammunition; terminated plans for future ammunition development; planned the phaseout of the 175mm gun; and commenced development of an "up-gunned" 8-inch howitzer. Accordingly, the original SOR, was revised and superseded in October 1969 The MCLGM was directed to be an 8-inch gun in production using the basic design established in the development of the 175mm prototype To meet these new requirements, a program was authorized in February 1971 to convert the prototype MCLGM from its l75mm/60 configuration to an 8"55. Thus, the Naval Weapons Laboratory was assigned the responsibility to effect this conversion and to evaluate the 8"55 MCLGM MARK 71 MOD 0.

The 8"/55 Major Caliber Lightweight Gun Mount MARK 71 MOD 0 consists functionally of three systems. A gun laying system positions the gun while the gun loading system automatically loads single rounds of ammunition into the breech, completes the firing circuit, and disposes of empty cases. A control system regulates and monitors mount operations.

The shield is a streamlined aluminum cover that mounts on the carriage base ring to protect the above-deck components. The shield has a gun port on the front, left and right access doors, and a circular access cover on the rear. A gun port shield, through which the gun barrel protrudes, moves with the oscillating assembly, keeping the gun port covered. The gun laying system consists of the train and elevation system. The train system moves the rotating structure in the deck plane; the elevation system moves the oscillating assembly perpendicular to the deck plane. Both systems mount on the carriage.

The gun loading system loads ammunition into the breeeh, fires the round, extracts the empty cases from the breech, and ejects the case from the mount. Components of the gun loading system are: loader drum, hoist, cradle, rammer, case extractors, breechblock, empty case tray and empty case ejector, which are all powered by the lower an' upper accumulator systems. The loader drum, located below the stand and on the mount's vertical centerline, supports 25 ammunition clips. Each clip stores three rounds of ammunition and is positioned in a clip track on the drum.

Loading system tests were conducted on 24-25 September 1971, and train and elevation drive tests were accomplished 20-22 October 1971. Proof testing was conducted with the EX 28 MOD 0 liner on 3 September 1971 and with the EX 28 MOD 1 liner on 13 October 1971.

It can be concluded from the test results that the train and elevation power drives respond satisfactorily to local or remote orders from dummy directors. The loading system can sustain rates of fire between 11.7 and 12.6 rounds per minute in auto-load, can be cycled in step-load, and can select and load any of six types of ammunition which liave been predesignated. Misfires can be extracted and ejected through the empty case door, and a clearing charge can be loaded and fired without a man entering the mount.

The mount can be regunned in less than two hours provided the crew is experienced and the facilities and effort are well coordinated. Mechanical performance of the cartridge case and the primer, and the ballistics and flash of ihe propellant are not generally satisfactory. Excessive headspace (static clearance between the base of the case and the breechblock), and linear motion and axial expansion between the barrel and housing under dynamic loads are contributors to the marginal performance of the cartridge case.

The ballistic accuracy of the MARK 25 projectile fired from the mount was satisfactory, although the range tables for both the full and reduced charge are deficient and generally biased so that the projectile will fall longer than predicted (up to 3% longer). This bias is not unique with the 8"0 MCLGM. being related to the projectile and therefore noted in all 8"0 mounts.

Barrel life and velocity loss results were not conclusive due to the limited barrel erosion, however, barrel life to about twenty percent expended is roughly comparable to that of the 8"0 barrel MARK 16 and acceptable when using NACO propellant. Some minor deficiencies from a safety viewpoint were uncovered, however none were inherent or disqualifying. Smoke and carbon monoxide concentrations during firing make it unsafe to circulate the air in the mount to other spaces in a ship or to enter the mount for repairs until after the mount has been properly ventilated.

An extremely severe and arbitrary schedule prevented the contractor from completing all necessary work prior to commencement of the evaluation. No correspondence from the contractor was received indicating that the installation, conversion and his checkout were completed prior to the Technical Evaluation. problems were encountered throughout the Technical Evaluation with the cartridge assembly.

Based on results of the Technical Evaluation, the performance of the 8"/55 Major Caliber Lightweight Gun Mount MARK 71 MOD 0 was judged to be acceptable and certification for release to OPEVAL was recommended on 12 November 1971. The Operational Evaluation was begun under the auspices of COMOPTEVFOR on 15 November 1971.

During her major overhaul in 1974-75, USS Hull's forward 5"/54 Mark 42 gun mount was replaced with an 8"/55 Mark 71 gun mount. A prototype gun and mounting had been built and tested ashore during the early 1970s. Hull was its test ship for seagoing trials, after which it was expected that several of these guns would be installed on board destroyers of the new Spruance class. Hull's eight-inch gun began firing tests in April 1975. These lasted into the following year, and were reportedly successful. On 30 June 1976 a new major caliber lightweight gun mounted in destroyer Hull (DD 945) successfully fired an 8-inch laser-guided projectile developed jointly by the Navy and the Marines. The ship carried the Mark 71 mounting during her 1976-77 and 1978 deployments to the Western Pacific, and conducted more firing tests during that time.

As of February 1978 it was planned that the Major Caliber Lightweight Gun (MCLWG) would enter production in FY 1980. It was to be backfitted on thirty DD-963 Class ships, twenty-four of which are then under construction. The MCLWG with SEAFIRE, the guided projectile, the Improved Conventional (Cannister) Munition (ICMs) will be controlled by the MK-86 gunfire control system and provide an anti-surface capability for the DD-963. SEAFIRE is a fire control system capable of operating in an ECM environment. The system will provide target designation to the horizon for directing guided projectiles. In addition, a SEAFIRE pod for the LAMPS helicopter will allow over-the-horizon targeting.

An example of a program for which risk was not adequately considered when the ACAT was assigned and the decision authority determined is the Major Caliber Lightweight Gun (MCLWG). Based on funding levels, the program was designated ACAT II with CNO as the decision authority. When the program experienced difficulties during Operational Evaluation (OPEVAL) the newspapers publicized the problems. This led Congress to request a GAO investigation. Not only was SECDEF unprepared for questions, but SECNAV and CNO did not have a coordinated position on how to resolve the problems. Because of the high- level attention focused on the program, the decision authority was raised to the SFCDEF level.

The MCLWG would complete development in 1976, but by 1975 DoD had not established which ship classes might carry this weapon. In June 1976 a Naval Postgraduate School research project titled 8 Ammunition Development Study was initiated by the Cornmander, Naval Sea Systems Command . The research was to focus on various studies with regard to ammunition development for the 8 major caliber lightweight gun (MCLWG). There are three relatively independent subassemblies in the propelling charge, namely the case, the primer, and the propelling charge itself.

Cases can be fabricated of drawn brass, drawn steel, spiral wrapped steel, or other materials, the most promising of which is fiberglass. The existing inventory of cases is fabricated of drawn brass, the technology is well understood , and the problems are well defined. Various advantages led Army Ordnance to favor spiral-wrapped steel cases whenever they are certified. In 105mm tank rounds, for example, cases were available in drawn brass, drawn steel, and spiral-wrapped steel.

For primers the major options are to rework an existing inventory, to redesign the primers using the traditional technology, or to redesign the primer using more advanced technology. A complete redesign certainly showed promise of significant operational improvements, although each specific alternative has its problems. A number of developinent efforts on primers was currently underway.

Propelling charge options address the chemical composition (NACO or M1A1) and physical characteristics (grain size). Since NACO is a Navyspecific formulation and M1A1 is used extensively by the Army, a switch to M1A1 by the Navy would be a move toward joint procurement, in line with DOD policy. They are of virtually identical chemical compositions. Current Navy practice calls for 7-PERF propellant grains. There may be some advantages in interior ballistic qualities by going to the larger l9-PERF grain size. The larger grains have greater inter-grain spaces, enabling ignition gasses to penetrate more readily, thus giving more uniform ignition.

The Navys 8-inch Major Caliber Lightweight Gun for surface combatant ships was confronted with significant performance problems. In GAO's August 1978 classified report on the gun, GAO noted that internal DOD studies had raised questions about the advisability of procuring it. The gun was to be deployed on Spruance class destroyers, which probably would not be available for amphibious assault operations or shore bombardment - two of the guns primary missions - because the Spruance class destroyers would likely be committed to higher priority roles. Also, the range of hostile missiles was much greater than the guns range, which could force the destroyers to remain at distances beyond the effective range of the gun.

Despite these and other concerns, the Secretary of Defense approved the gun for limited production. The Congress refused to support acquisition of the gun, and the program was terminated. The Major Caliber Lightweight Gun (MCLWG) program was suspended August 1978. The Navy indicated plans to install a 8-inch gun when it became available, but nothing came of this idea.

Mark 71 8in/55 (203 mm) Major Caliber Lightweight Gun [MCLWG] Mark 71 8in/55 (203 mm) Major Caliber Lightweight Gun [MCLWG] Mark 71 8in/55 (203 mm) Major Caliber Lightweight Gun [MCLWG]



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