8"/55 Gun

Chapter XI

a. Introduction

The 8"/55 guns used as the main battery for cruisers during World War II included the two-gun turrets on ships of the PENSACOLA class, the 8/55 triple base ring mounts with hoists and the 8"/55 three gun turrets. A great deal of modernization was undertaken after Pearl Harbor to bring these turrets up to date. An example of this was the design of simple and reliable powder hoists in the 8"/55 turrets of the BALTIMORE class. Much old elevating and training equipment had to be modified and practically all of it had to be relocated and rearranged and space found in gun pits and handling rooms which were already crowded with gear.

The most outstanding development in this type of gun was the design of the extremely advanced, rapid firing 8" turrets for cruisers of the CA139 class. Although this turret had a nigh priority throughout its development, it did not reach the service during the war.

b. History of the 8"/55 Caliber Turret for CA139 Class

In May 1943 the Bureau of Ordnance initiated the de-



sign of an 8"/55 rapid fire turret, capable of being loaded at any angle from -5° to 41°. This design had several unique features. It was the largest case gun built to date. It had elevating arc and pinion gear instead of oscillating bearing and elevating screw. It also had a "loose liner" which left enough clearance between the liner and the tube to permit removal and replacement of liners without the gun barrel being returned to heating pits. The gun had a housing and vertical sliding wedge breech block instead of a screw-box type breech mechanism.

The new rate of fire was expected to be about eight rounds per gun per minute. The slower rate of fire of previous 8" turrets was due primarily to the use of powder bags with the resulting need for extensive safety precautions and also the necessity of manual loading at on angle of elevation. It was believed possible to obtain high speed loading at any angle of elevation by using semifixed ammunition, mechanically handing the ammunition from hoist to slide, and by power ramming the case and projectile with one stroke. The handling of ammunition from the time it entered the lower end of the ammunition hoist until the time it left the gun was to be entirely automatic.


The transfer of ammunition between hoists and slide rammer trays was to be accomplished by cradles which would swing about the gun trunnions. The shell cradle was to contain an automatic fuze setter which would make dead time constant when the turret was fired in "Full Automatic!"

New features or this design also included automatic case disposal through the turret face plate, hydraulically operated sliding wedge type breech blocks, and elevating arcs and pinions.

In the early design work on the turret, it was deemed advisable not to include rangefinders since radar could be used for the same purpose, however, certain officers in the Bureau of Ordnance wished to have turret rangefinders put in because of the possibilities of radar jamming. After considerable study, It was decided that the space and weight requirements of an optical rangefinder were too great to allow their inclusion in this turret. A compromise was made to the effect that the authorized 15 ft. rangefinder in the Mark 54 director would be replaced by a 26' 6" rangefinder and that two radar sets would be installed in the turret. Since


there was now a considerable amount of space in the turret officer's booth it was decided to have the gun captains here. From a vantage point directly behind the gun and in the turret officer's booth, each gun captain would have conveniently centralized control and indication of slide, hoist, and fuze setting regulator operation through his individual control panel.

Considerable attention was also given to the desirability of a two or three gun design as opposed to a twin or triple turret. Although separate slides cost more in weight, having two or three guns in one slide meant that a casualty to one gun could not be cleared while the other guns were firing. The Bureau of Ships recommended that a two gun turret be designed on the basis that it could be used in the CA68 class hull. However, the General Board expressed a preference for a complete new design of a ship with three 3-gun turrets, and this choice was finally approved.

It was decided to build CA's 139 to 142 to the new design. Later CA's 134, 143, 148 and 149 were added to the list. The end of the war and the accompanying



out-backs in the construction program brought about the cancellation of all but CA's 134, 139, 140, 141, and 148.

Space for a sight for the center gun in this 8" turret was very limited. For this reason and also in order to simplify sights as compared with those in the CA68 class, It was proposed to use the following sight and control arrangements: 

(a) To provide only one pointer, trainer, checker,and sight setter for each turret.

(b) To provide the pointer with a sight, an elevation indicator, and an elevation order synchro transmitter for local control.

(c) To equip each gun with its own regulator and complete elevating gear. Normal control of guns, either in automatic or local, was to be via the respective regulators and speed gears.

(d) The pointer's sight was to De driven in elevation by the gun slide and receive sight angle from the sight setter.

(e) The regularly used gun elevation input to the elevation indicator and sight was to be driven by the gun adjacent to the pointer.


The above arrangement of an elevation regulator was believed acceptable, based on past experience which bad proved that the regulators were as rugged and reliable as the speed gears they controlled.

Realizing that the problem of stowing and handling the 8" cartridges should be solved experimentally, the Bureau of Ships authorized the David Taylor Model basin to do this work. Numerous tests were carried out on a rolling platform and the final decision was to stow the cartridges on their bases in the magazines and move them by small hand trucks.

Tests were also carried out at the David Taylor Model Basin on the handling of 335-- pound projectiles for the 8"/55. As a result, all projectiles were to be carried on rotating rings on the rotating structure. To insure the stability of the projectiles during transfer from ring to hoist, a steadying arm was developed by the model basin. The arm was taken over by the Bureau of Ordnance and further developed so that it could be used in the turret.




In order to ascertain whether the strength and rigidity of the structure was sufficient, the Bureau of Ships authorized the David Taylor Model Basin to manufacture and test a 1/10 scale still model of the rotating structure of the 8" turret. The following factors were to be investigated:

(a) Safety of the structure as determined by static loading on the trunnions.
(b) Angular deflection of & trunnion block caused by firing on a wing gun.
(c) Angular deflection of a trunnion block caused by a 30° roll of the ship.

Test results showed that only moderate stress w s encountered at critical points and that angular deflections were within acceptable limits.

A 1/5 scale model of the breech clock housing and rear guides was also constructed and tested at the Model Basin. When the war ended test results had not been analyzed.

The use of semifixed ammunition was a new idea for 8" guns. For this reason and because the rapid firing of



the gun was expected to heat the gun chamber considerably, it was necessary to provide some means of clearing the gun after a misfire. It was decided to provide one short case per gun which could be fired by any of the following means:

(a) Regular electric firing circuit.
(b) An auxiliary electric source using the regular flexible firing leads.
(c) An "electric wand" providing current direct from an electric source to a contact located conveniently on or near the breech block.
(d) A detachable percussion firing device which is attached at the rear of the housing and operated by pulling a lanyard.

Present tests indicate that after 100 rounds continuous rapid fire cookoffs of the propellant charge or projectile were very improbable.

It should be noted that the regular case was fired only by electrical means. The decision to have only an electrical primer was based on the safety involved in handling and on the desirability of eliminating the need to remove the cartridge case from its container in the



magazine. The operation of removing the cartridge case from its can was considered slow and tedious.

For the first time in the history of the Bureau of Ordnance it was decided to manufacture a pilot turret which would be used for extensive tests at the Naval Proving Ground, Dahlgren to make sure that all the ordnance machine and equipment functioned smoothly and properly. The Philadelphia Navy Yard was authorized to build the structure, the Bureau of Yards and Docks provided the foundation at Dahlgren and the Naval Gun Factory assembled the complete pilot turret. The Philadelphia Navy Yard provided compensating weights for the pilot so that it would have the full moment of inertia of the final turret; portions of the compensating weights representing the projectiles carried in the turret were too readily removable.

Numerous delays were encountered in the manufacture and assembly of the pilot. It was originally scheduled to be ready for test of July 1, 1944 but at the end of the war it was estimated that it would not be ready for testing until March 1, 1946. The major reasons for the delay was the contracts were given to manufacturers well esta-



blished in Navy work who already had many commitments of higher priority. The production work of these manufacturers during the war was of necessity on equipment which was well out of the experimental stage. This was the case at the Naval Gun Factory as well as with private manufacturers.

The David Taylor Model Basin also had future plans to run numerous strain tests on the pilot turret to correlate the check data obtained on scale models. This would furnish an estimate on the value of the scale model for obtaining strain measurements.

In addition to the pilot turret, two single combination firing and assembly girders tone right and one left) were constructed. They remained at the Naval Gun Factory for assembly and test purpose. The girders were to be sent from time to time to the Naval Proving Ground for proof firing on ordnance equipment when the pilot turret was not available for firing.

When the design had progressed to the point where a balance could be made, the trunnions were moved back approximately four inches in order to balance the oscillating


weights. The Bureau of Ships suggested a reduction in the length of the gun barrel from 55- to 50-caliber to relieve interference difficulties as veil as to reduce the unbalanced condition. The Bureau of Ordnance finally decided to move the trunnion back and retain the 55-caliber length. The decision was based on the fact that the shorter gun barrel would erode more quickly if the muzzle velocity were kept the same.

In view of the relatively poor acceleration control now provided by hydraulic regulators, their inability to filter out roughness in the input signal to the regulator, and the extensive leakage of oil from hydraulic regulators, serious consideration was given to the use of amplidyne equipment in lieu of hydraulic equipment for driving and controlling the elevating gear. Space requirements for the amplidyne controlling and drive equipment were, however, considerably greater than for the hydraulic equipment, and for this reason it was decided to use the old type hydraulic equipment despite its inherent drawbacks.

General Specifications were jointly prepared by the


Bureau of Ordnance and the Bureau of snips to cover the tests to be conducted at the Naval Proving Ground. This was also a "first" in that never before had such a complete and comprehensive test program been set up by the Bureau of Ordnance. Previously, testing had been some what hit-and-miss proposition; the Naval Gun Factory and the building yards would run spot checks on individual pieces of equipment as were desired or requested from time to tide.

In view of the experience of the BOISE during the war it was decided that the following locations be flame-proofed in both directions:

(a) The lower end of the S" powder hoist.
(b) Space from the magazines to the handling room.

In January 1, 1945 the Bureau of Ordnance recommended to the Bureau of Personnel that a training program be initiated us soon as possible for Chief Turret Captains who would later be assigned to the prospective crews of the CA139 class . Such special training was considered necessary because of the large amount of new complex auto-


equipment. The recommended program included:

(a) Training in the design, manufacture, and installation at the Naval Gun Factory.
(b) Further training and experience at the Naval Proving Ground on testing of girders and pilot turret to familiarize the crews with modifications, repairs, and maintenance incident to the experimental firings.
(c) Training at plants of various contractors who were designing and manufacturing equipment for these turrets.
(d) Assisting at the building yards in order to insure proper installation of equipment in the ships of its proper operation after completion of the ships.

To provide for the complete training of the personnel to be assigned duty in these turrets, a cycling girder was furnished the Gunner's Mate School, Navy Yard, Washington, D. C. The girder was complete with all electric-hydraulic power and control equipment, a fuze setting receiver regulator, fuze setter, and the latest design of gun captain control panel. The equipment was capable of following a


dummy director signal in automatic and the handwheels in local. It is also capable of cycling ammunition at a single elevation, which permits the simplest design of handling equipment.

It was necessary to get the design of the rapid fire 8" turret out In a hurry to accomplish the design as suggested to the General Board and approved by them for inclusion on the new heavy cruiser within two and one-half years, from the start It was realized that this could be done only with very close coordination between the Bureau of Ordnance, Bureau of Ships, the Philadelphia and yew York Navy Yards, Naval Gun Factory, and the various private detailing and manufacturing concerns. After the Bureau of Ordnance had completed the layout of the slide, and had developed the detailed general arrangements of the turret, the Naval Gun Factory furnished 13 experienced
engineers and draftsmen; the New York Navy Yard sent two engineers to cooperate with six men of the Bureau on program. With this additional help the progress of design work went along very rapidly. As general arrangement plans progressed, unsigned blueprint copies


were forwarded to the detailing design activities. By working in this fashion with the detailing activities, a definite saving of time was accomplished. The detailing activities were able to release their signed drawings for manufacturers three weeks after the Bureau of Ordnance had completed their general arrangements. By getting assistance from the Philadelphia Navy Yard, the Bureau of Ships did likewise in the development of their part of the turret. By close cooperation between the bureau of Ordnance and Bureau of Ships, it was possible for both bureaus to complete their design at the same time.

It was approximately ten months from initiation to completion of the design. However, it should be noted here that optimum design features were sacrificed for speed, as in most cases the first layout was accepted.

Proof of the cycling girder at the Naval Proving ground snowed that the firing rate was between nine and ten rounds per gun per minute, several 100--continuous rapid fire bursts were fired proving that the design is very successful.


In order to obtain the maximum rate of fire possible, It was decided to experiment with the breech opening mechanism so as to initiate opening of the breech as close as possible to the time at which the powder pressure ceases to act. A new breech opening cam was designed and installed for test firing, and results indicated that the rate of fire would be increased one round per minute.

At the end of the war it was estimated that the 8"/55 rapid fire gun would be delivered for installation to CA134 prior to its scheduled commissioning in December 1946.


8"/55 Caliber Case Gun
(Turret Equipment)

Component Design Activity Detail
Mfg. Pilot
Mfg. for Ships
Guns BuOrd BuOrd NavGun NavGun
Slide BuOrd NavGun NavGun NavGun
Housing & B.M. BuOrd NavGun NavGun NavGun
Drives for Housing
& B.m., etc.
BuOrd Vickers Vickers Vickers
Powder Hoists BuOrd No. Ord. No. Ord. No. Ord.
Powder Hoist Drives No. Ord. No. Ord. No. Ord. No. Ord.
Sights, El, & Train
BuOrd NYd. N.Y. NYd. NY NYd. NY
Sight Hoods BuOrd NavGun NavGun NavGun
Projectiles Rings BuShips
NYd. Phila.
NYd. Phila. None BuShips
NYd. Phila.
Projectiles Ring
Vickers Vickers None Vickers
Deck Lugs
  (Trunnion Bearing)
BuOrd Standard
Mach. Co.
Mach. Co..
Mach. Co.
Firing & Lighting
BuOrd NYd. Phila. NavGun. NavGun
Train Gear BuOrd NYd. Phila. NYd. Phila. NYd. Phila.
El. Gear BuOrd NavGun NavGun NavGun
Train & El. Drives W. T. Co. W. T. Co. W. T. Co.. W. T. Co.
Train & El. Regulators F. I. Co. F. I. Co. F. I. Co. F. I. Co..
Projectile Hoist BuOrd No. Ord. No. Ord. No. Ord.
Parbuckling Gear BuOrd NavGun NavGun NavGun
Proving Ground
NYd. Phila.
NYd. Phila. NYd. Phila. None
Turret Gen. Arrangement BuOrd NavGun None  
Structure (Turret) BuShips
NYd. Phila.
NYd. Phila NYd. Phila. Shipyards
Parbuckling Drive BuOrd NavGun None NavGun
Projectile Hoist
No. Ord. No. Ord. No. Ord. No. Ord.
Right& Left hand
  Cycling Girder
NavGun NavGun    

No. Ord.   -  Northern Ordnance Incorporated
F.I. Co.     -  Ford Instrument Company
W.T. Co.   -  Waterbury Tool Company


c. Production Program for CA68-75 and 122 Class

In October 1941,240 of the 8"/55 guns were installed on heavy cruisers, available for spares, or being relined it the Naval Gun Factory. Approximately 90 were on order for ships under construction.

The CA68 BALTIMORE class was authorized to carry the 8"/55 three gun turret. The Naval Gun Factory was the outstanding producer of this type gun. Several commercial firms were engaged in producing component parts for the 8" turret, all of which produced in a generally satisfactory manner. The powder and projectile hoists were produced entirely by the Jeffrey Manufacturing Company. Blaw-Knox Manufacturing Company made 84 slide castings starting in 1941. Of this quantity, Nordberg finish-machined 44 and the Gun Factory handled the balance. Deliveries castings for the first three ships were critical because of the poor grade of castings received from Blaw-Knox. Their technique was Investigated and improved, later deliveries were entirely satisfactory. All the lights were furnished by the General Mills Company, which after a very bad start due to keeping within tolerances of an intricate gear training, produced 84 excellent sight mechanisms. General Mills also produced all of


the necessary training and gun attachments. The Midvale Company made all the recoil cylinder forgings, and all rammers were fabricated by the Goodman Manufacturing Company.

Under the war production program, no 8"/55 turrets were produced until 1942 when four units were delivered for new construction. Ten were delivered in 1943 and 9 in 1944. At that time, reserve stock spares were n satisfactory condition with replacements on hand or tearing completion, Nine units were delivered through November 1, 1945. Components for an additional 19 turrets were stopped in various stages of completion because of ship cancellations.

During the entire program, a total of sixty-two three gun assemblies were delivered at an approximate cost of one million dollars for each assembly.[1]


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Transcribed and formatted by Thomas Wildenberg, HyperWar Foundation