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USS MULLINNIX DD-944




The picture of the Mullinnix below is an "image map"
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Historically the Mullinnix Was
Very Unique
Among the many "lasts" of the Mullinnix include:

  • The 5" 54 - the last gunmount that had gunnersmates inside during fire missions
  • Last all gun destroyer class in US Naval history
  • Last active all gun dostroyer in US Naval history
  • Last of the 3-inch/50-cal. rapid-fire twin mounts

  • Ammo, Ammo, and More Ammo

  • Main Battery Salvo Alarm


Main Armament - 5" 54 MK 42


The 5" 54 MK 42



The main armament of the FORREST SHERMAN-Class destroyers, CHARLES F. ADAMS-Class guided missile destroyers, MITSCHER-Class destroyer leaders, FARRAGUT-Class and BELKNAP-Class guided missile destroyer leaders, the nuclear guided missile destroyer leader TRUXTON, and the KNOX-Class destroyer escorts, was the rapid-fire 5-inch/54-caliber Mark 18 gun with a housing for a vertical-sliding breech block.

It was a single arrangement enclosed in the Mk 42 gun mount. The basic round for the MK 18 gun was semi-fixed, with a 70-pound projectile and a 34.5-pound shell case that included a 19-pound powder charge. The initial velocity of the round was 2,650 feet/second with a maximum range of 25,909 yards at 47 degrees elevation and a ceiling of 48,700 ft. at 85 degrees elevation. The Mk 42 Gun Mount was the next generation of the Mk 39 mount which was the original armament of the MIDWAY-Class carriers. The Mk 42 mount was a shielded, base-ring-type mounting consisting of a gun house and carriage with rotating structure, a fixed stand for mounting the base-ring, and the gun loading system.

The gun house was the armored portion of the rotating structure that contained the gun and slide assembly, gun-laying equipment, and fire control equipment. The rotating component transferred the rounds from the stationary gun loading components to the breech, set MT fuses, rammed the rounds, aimed the gun, fired the gun, extracted the empty powder cases, and ejected the cases from the mount. The gun house rested on a heavy framework supported by the base-ring assembly. The base-ring rotated on roller bearings within a fixed stand that was bolted to the deck. The loading system for the MK 42 mount consisted of two rotating loaders in the handling room adjacent to the magazines, lower hoists, transfer stations, upper hoists, cradles, and transfer trays. Each loader had two independently driven drums, the upper drum for projectiles and the lower drum for powder cases. This arrangement allowed different types of projectiles to be loaded. Each drum held twenty rounds and loading doors on the drums five-inch guns. allowed ammunition handlers to continually replenish the drums. The lower hoists raised the paired rounds, which remained together throughout the loading operation, up to the transfer stations in the carrier room and transferred the rounds to the ammunition carriers.

The ammunition carriers were mounted on the center column in the carrier room. The tubes rotated around the center column until aligned with the upper hoists. After transferring the rounds to the upper hoists the empty tubes rotated back into alignment with the lower hoist transfer stations. The upper hoists, also mounted on the center column, moved the rounds to the right and left cradles in the gun house. The cradles pivoted on the slide trunions to convey the rounds to the right and left transfer trays mounted on the gun slide. The fuse setters were also mounted on the slide just forward of the trays. Fuse setting orders were received electrically from the gun director or the plotting room and mechanically transmitted to the fuse on the projectile. The trays held the rounds for fuse setting and then lowered the rounds to the ram position. The round was then rammed and fired.

This dual loading system, which allowed rounds to be loaded alternatively from the right and left sides of the gun, enabled a high rate of fire to be achieved. The gun was touted as having a rate of fire of 40 rounds/minute in dual sided operation. The mounts could be rapidly trained at a rate of 40 degrees/second, elevated from -15 degrees to 85 degrees at 25 degrees/second, and loaded at any angle of elevation.





Secondary Armament - 3" 50




3" 50 Gun System                        

In early 1944 the Bureau of Ordnance began developing a 3-inch/50-cal. rapid-fire gun in both single and twin mountings. It was designed for use against the newer, faster, and heavier aircraft developed during World War 11 and especially the new jet-engine models. Suffering from postwar financial austerity, the first production models were not ready for the fleet until late in 1947 but the 3-inch replacement and conversion program was well underway when the Korean War began in 1950. Nearly all of the FLETCHER and SUMNER-GEARING classes had their 40-mm mounts replaced with the new 3-inch Mounts.

The 3-inch/50-cal. Mark 22 was a semiautomatic gun with a power driven automatic loader that fired a fixed AA (Anti Aircraft) or HC (High Capacity) round consisting of a projectile and a cartridge case crimped to the projectile. The average weight of the round was 34 pounds. The projectiles weighed about 13 pounds including a burster charge of 0.81 pounds for the AA round and 1.27 pounds for the HC round. The initial velocity of the round was 2,700 feet/second with a maximum range of 13,100 yards at 45 degrees elevation and a ceiling of 27,300 feet at 85 degrees elevation. The gun could fire at a rate of 50 rounds/minute.

The gun barrel was a mono-block cone-piece of alloy steel, rifled and chambered for fixed ammunition, and chrome plated for its entire length. The gun was secured to the housing, which contained the vertical sliding-wedge-type breech block, with a bayonet type joint using interrupted screw threads. This arrangement greatly facilitated regunning. The gun and housing were supported by the slide, which allowed the gun to move in recoil and counter-recoil. A hydraulic cylinder stopped the gun recoil. A large counter-recoil spring returned the gun forward into battery. The power-driven automatic loader, consisting of a feed mechanism, a transfer tray, and a shell-carriage mechanism, each mounted on the after pan of the slide. It was a hopper feed mechanism with right, center, and left shaft-and-sprocket units. Ammunition was loaded into the right and left revolving sprockets that immediately moved the rounds to the center. The center sprocket alternated to accept a round from either side and in turn placed the round into the transfer tray and shell-carriage unit. The round was then lowered into line with the gun bore. The shell carriage was secured to an endless rammer chain that moved forward in the transfer tray, catapulting the round into the breech of the gun. Expended shell casings were caught in the ejection chute and directed forward away from the gun crew.

The new guns were fitted to both single and twin mountings. The single was to be exchanged for a twin 40-mm. mount and the twin for a quadruple 40-mm. mount. Although intended as a one-for-one replacement for the 40-mm. mounts, the final version of the new 3-inch mounts was heavier than expected, and on most ships the mounts could be replaced only on a two-for-three basis. The mounts were of the dual purpose, open-base-ring type. The right and left gun assemblies were identical in the twin mounts. The mounts used a common power drive that could train at a rate of 30 degrees/second and elevate from 15 degrees to 85 degrees at a rate of 24 degrees/second. The stands for both the twin and single mounts were virtually identical to the twin and quadruple 40-mm. mounts, respectively. This similarity greatly facilitated their installation. In many cases, however, the gun foundations below the stands had to be strengthened. Equipment mounted on the base ring and carriage above the stand included the gun pedestal, platform assembly, gun assemblies, and training and elevating mechanisms.

During the destroyer Fleet Rehabilitation And Modernization (FRAM) program of the 1960s the destroyers that were modernized had their 3-inch guns removed, however, those that did not undergo FRAM kept most of their 3-inch guns and as of this writing they survive in a few foreign navies.

© 2015 by Frank Wood, All rights reserved.
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