The history of 3"/50 caliber double purpose gun mounts during World War II was one of great production coupled with development in new and existing types. In 1939, when an inventory was taken of the number of these guns installed on U.3. Naval vessels and in store, it was found that approximately 690 were in existence. At the end of the program In 1945, 14,002 had been produced at an approximate cost of $223,808,000. The 3"/50 gun mounts were Installed principally aboard the Merchant Marine and auxiliary vessels of the United States Naval Service. Approximately 1,200 were manufactured under lend-lease, the great bulk going to Britain and Russia.
The 1939 inventory showed that in addition to the 690 mounts which were Mark 11, there was an excess of some 900 gun barrels. In order to utilize these barrels an interim type mount was designed by the Bureau of Ordnance and designated
Mark 20 Mod 1. In the meantime the Research Division of the Bureau of Ordnance designed a new 3"/50 mount for antiaircraft use. This mount became the Mark 22. Early in 1945 the first power driven 3"/50 caliber mount was developed and designated Mark 26. It resulted from the installation of power drives and other new components on a 3"/50 caliber mount Mark 22 Mod 0, 4, 17, or 20. The mount was operable in automatic, local, or manual control. Specifications required that it train (in power) at speeds up to 30° per second and elevate or depress at 24° per second. The principal new equipment of this mount was the train power drive Mark 31 and elevation power drive Mark 31. These all-electric drives, manufactured by the Arma Corporation, were furnished for 440-volt AC, 230-volt DC, and 115-volt DC power supplies.
During 1942 when requirements were increasing rapidly and the Research Division was overloaded with work, the Northern Pump Company was given
the project of designing for commercial manufacture a new 3"/50 double purpose single mount. This was eventually designated the Mark 24.
Design of the 3"/50 caliber rapid fire mount Mark 27 was initiated during the war but did not reach service. The mount was developed to provide heavier close-in antiaircraft coverage. The mount weighed approximately 30,000 pounds and was designed as a substitute for 40mm quads. It was expected that the first prototype would be ready for tests during 1946.
The first installation authorized for submarines was the 3"/50 caliber gun mount Mark 21 wet type. A total of only 117 was required in 1941 and these were produced by Walter Scott and Company Inc., Plainfield, New Jersey, however, this weapon did not prove effective and the Bureau designed a 5"/25 mount as a substitute.
In 1945, The Bureau of Ordnance started design of a new 3"/70 machine gun and mount. It was anticipated that the mount would require about flour years for development even though the project had been given a high priority, bureau officers
considered this assembly necessary for future close-in machine gun defense against guided missiles and the larger, heavier, higher-speed bombers which undoubtedly would be developed. The following high performance requirements for this new weapon were established; rate of fire 90 shots per gun per minute, automatic control, on-mount radar completely automatic handling from magazine to breech by an on-mount unit, muzzle velocity of 3400 f.s., use of VT fuze only, use of two guns in one slide. The magazine was to be on the deck below and was to rotate with the mount in train. The 3"/70 gun barrel had its origin of bore rounded off with a curve of long radius and its rifling grooves were tapered in depth from the breech toward the muzzle so that the last few inches at the muzzle were smoothbore. This design was intended to reduce the velocity loss per round and to provide the most accurate flight obtainable.
D. Dual Purpose Mounts
1. Single Mount Mark 24
In 1942, due to the increasing demands for 3"/50 guns, the Northern Pump Company undertook the design of a 3"/50 caliber mount capable of being manufactured at a minimum rate of production of 300 a month. The first mount was ready for proof in six months from the date of contract.
The mount was capable of being set up both on small vessels and on shore. The carriage and slide were of welded construction and the mount carried the standard Mark 21 gun. The mount used roller bearings in trains instead of the ball bearings of the older Mark 22 Mount.
The maximum rate of fire varied between approximately 33 and 15 pounds per minute between 15° depression and 86° elevation. The gun was serviced by hand over the deck.
An electric power drive was developed in 1944 by the Arma Corporation, Brooklyn, New York. The drive was made for the 3"/50 caliber mount Mark 22 and Mods
and could be adapted to the Mark 24.
In 1944, a concentric ring type open sight was developed for Installation on 3"/50 caliber mounts Mark 24 and Mods installed on Naval and merchant vessels. This sight was to replace the Optical Ring Sights Mark 2 originally installed on these mounts.
2. Single Mount Mark 22
The 3"/50 caliber assembly Mark 22 was a dual purpose pedestal type single gun mount designed by the Bureau of Ordnance before the start of World War II for antiaircraft use. It was an open mount with flange-bolted stand deck emplacement. The mount, equipped with manual train and elevating drives, did not have power equipment and was manually served. In 1945, power drives, developed by the Arma Corporation, were added to certain Mark 22 mounts and these mounts were designated Mark 26. Some Modifications of the Mark 22 mounts were equipped with train and elevating gun attachments which provided dial indication of gun train and elevation order transmitted electrically from the controlling direc-
tor or target designation transmitter. These mounts were also equipped with indicator-type fuze setter and remote-control electric firing arrangement.
The weight of a 3"/50 Mark 22 mount was approximately 8,000 pounds; maximum range, surface fire 14,600 yards; and the muzzle velocity 2,700 ft. per second.
The maximum angle of elevation was 85 and the maximum angle of depression 13°.
The Gun Mark 22 was a monobloc alloy-steel piece with chromium-plated bore and uniform twist rifling. The gun barrel was attached to the housing by bayonet-type thread engagement. A key prevented rotation of the barrel with respect to the housing. The Gun Mark 22 was similar to Gun Mark 21 except that a tapered collar was added to chase, approximately 78 inches to the rear of the muzzle. The 3" Gun Mark 22 can be used with either Mount Mark 22 or Mark 24.
The slide Mark 22 was an assembly of a cast steel gun slide element with integral trunnions, and a lower casting for mounting a single recoil cylinder mechanism and the elevating arc.
c. Twin Mount Mark 27.
Early in 1945 the Bureau of Ordnance started development of a 3"/50 rapid fire twin mount to provide heavier close-in antiaircraft coverage. The mount Mark 27, on which development has not been completed will weigh approximately 30,000 pounds and will consist of 3"/50 Mark 22 nod 3 guns mounted on a 40mm quad stand. A single 3"/50 gun, similarly, is to be mounted on a 40mm twin stand. The mount will have a conventional pointer and trainer and will be served on the deck (although there is a possibility that one-man control may eventually be developed.) The weight of the 3"/50 twin mount and its ammunition is comparable to that of a 40mm quad and its ammunition. The weight of a 3"/50 single mount and its ammunition is comparable to that of a 40mm twin mount and its ammunition.
A rate of fire approaching 50 rounds per gun per minute is expected and it is planned to use VT fuzes only. This rapid fire feature has been achieved by power-operated feeder loaders, each being loaded from both sides.
The design of the power drive for the 3"/50 Twin Mount Mark 27 has been slowed since the cessation of hostilities. It is expected that two development mounts will be ready for test In the spring of 1946.
d. Production Program
1. Schedule of Requirements
In 1939 contracts were awarded to the Miehle Printing Press Company, Blaw-Knox Company, and the Baldwin Locomotive Works for the production of 900 mounts, Mark 20 Mod 1, the interim type mount. The major portion of this work was allotted to Miehle, with contracts with this firm calling for delivery of approximately 530 mounts.
Upon completion of the design of the new 3"/50 mount Mark 22 in 1940 it was estimated that the requirements for all 3"/50 guns, dry type, totaled 7,250. This included the 692 on hand at the time of the 1939 Inventory and the 900 interim-type mounts under contract. Also included in the requirements were 1,220 mounts under lend-lease.
In the production of the original 900 mounts by commercial manufacturers, the quality of the product and the quantity attained by the Miehle Printing Press Company led the Bureau of Ordnance to believe that this concern could be expanded to become the backbone of the 3" program. As a consequence the Mark 22 mount was made principally by this Chicago concern, with the ultimate result that this company produced in the neighborhood of 12,000 mounts.
The original requirements for 3"/50 assemblies were greatly Increased from time to time. In July 1942, by a directive summary the overall requirement indicated a total program of 12,000 assemblies including those already on hand or on order. In December 1942, by a directive summary, production requirements were revised upward to a total of about 15,000 with an indication that requirements might be even further increased. In April 1943, requirements were again increased to approximately 19,000 assemblies with a
delivery rate of 725 per month. In October 1943,this schedule was revised to level off at about 400 assemblies per month.
The rate of 725 assemblies per month, scheduled in April 1943, was established as a result of oral representations to the Bureau of Ordnance from the Office of the Vice Chief of Naval Operations that the Bureau accelerate the 3"/50 production with a view to reducing the then existing deficiencies in the supply of this weapon, as well as with a view to making available additional weapons to increase the armament of merchant ships. At the end of September 1943, when deficiencies in the supply of 3"/50 assemblies (based on one 3"/50 per merchant ship) were being wiped out, VCNC put the merchant ship arming plan on the firm basis of one 3"/50 per merchant ship, except for certain selected groups. In order to balance the reduced requirements resulting from this plan, the 3"/50 procurement was readjusted in October 1943 to a reduced schedule of 400 assemblies per month.
After this time, requirements continued to be reduced until September 1944, when production of 3"/50 mounts was cut back to approximately 14,000 for the entire program. Production of 3"/50 assemblies by commercial firms was terminated in the fall of 1944; production by the Bureau of Ordnance ceased in March 1945. The most noteworthy production rate obtained by any manufacturer was that of the Miehle Printing Press Company who reached a rate of 475 mounts per month Just prior to the termination of the 3"/50 program In 1944.
Very few difficulties were experienced during the period of production of 3"/50 mounts. Perhaps the only serious one resulted from the substitution of material under original specifications in the roller paths. Because of this defect mounts were chattering in train, but new parts were supplied and the defect disappeared.
The Northern Pump Company completed the design of the 3"/50 Mounts Mark 24 in 1943. At that time they
were awarded a contract for the production of 2,000 of these mounts. However, because of the unusually large requirements for 5"/38 hark 37 merchant mounts which this contractor had also designed and was manufacturing, the 3"/50 contract was reduced to 500, the remaining 1,500 being assigned to Naval Ordnance Plants for completion. However, just as the plants were getting into production and almost ready to assemble and ship the completed mount, the requirements were reduced and only two mounts were produced.
With respect to the mounts for lend-lease, the British insisted that several components be changed for their use, the principal one being the sight mechanisms, however, after approximately 100 of these mounts had been installed, the British decided that the regular USN Mount Mark 22 was superior to theirs. Consequently, the undelivered quantity was canceled and the bureau was obliged to convert the remaining Mark 22 mounts made to British specifications to Mark 22 Mod 17 for American use. The conversion of these mounts was accomplished by the Walter Scott
Company, Plainfleld, New Jersey.
4. Power Drives
The design of 3"/50 power drives was completed in the spring of 1944 by the Arma Corporation, at that time, the bureau of Ordnance was authorized by a directive summary to procure 2,000 power drives for installation on U. S. ships having a battery of three or more 3"/50 guns. However, in the fall of 1944, when the program reached a directive stage for authorization of actual procurement it was decided that 1,000 drives would be sufficient to start the program and the contract for this number was placed with the Arma Corporation.
Initial deliveries of power drives were expected during this first quarter of 1945 but due to the difficulty of obtaining a satisfactory design of certain components and to procurement difficulties with subcontractors, the initial supply of 3"/50 power drive equipment was not available until August 1945. Following VJ Day, procurement of drives was reduced to 600; of these, 500 were to be used on 3"/50
caliber mounts Mark 22 scheduled for ships of the post war fleet In which 3^50 caliber guns are a part of the ultimate approved armament. The remaining 100 units were reserved for the 3"/50 single rapid fire development.
5. Associated 5"/50 Equipment
Three-inch firing and lighting circuits were produced mainly by the Clark Controller Company, Cleveland, Ohio and the Penn Electric Switch Company, Goshen, Indiana, both of which produced in the quantity and rate desired. However, this was an extremely difficult problem because of the fact that it was necessary to buy various types of circuits for the different types of electrical power supplied aboard ship.
The 3"/50 loading machine was produced by five different manufacturers, none of which was particularly outstanding, out the resulting production was sufficient for the Bureau's requirements. According to a Cominch directive, one 3"/50 caliber leading machine was provided for each vessel having three or more gun batteries.
Elevating and training gun attachments were produced principally by the Morey Machinery Company, New York, who supplied 2,600 units of this item. The balance of 1,000 were furnished by the General Electric Company, Schenectady, New York. Some difficulty was experienced in attaining the desired delivery from General Electric.
The 3"/50 fuze setter was produced by a large variety of manufacturers including the Naval Gun Factory. The outstanding manufacturers in this group were the Southwest Pump Company and the textile Machine Works.
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