TECHNICAL INFORMATION REPORT 3-1-3M2


OFFICE, CHIEF OF ORDNANCE
APRIL 1954

DEVELOPMENT
OF
120-MM GUN TANK, T57


120-MM GUN TANK, T57

In 1948-1950, when the development of the T43 120-mm gun tank was being planned and the project for the T43 was in its first stages, several attempts were made to incorporate automatic ammunition-handling equipment in the new tank's turret. In each instance, the space limitations imposed by the over-all design of the turret made this impossible. However, the Army Equipment Development Guide, issued in December 1950, emphasized the need for incorporating power ammunition-handling equipment and guns of the shortest recoil attainable in the design of new tanks. Although not applied to the T43, these new requirements encouraged the Ordnance Corps to expedite the development of what promised to be a solution of the ammunition-handling problem.

For some months, studies relating to the design of an oscillating turret had been conducted in connection with plans for the T69 experimental 90-mm gun tank and the project for developing the T43 120-mm gun tank. Work on this problem was now accelerated. As tentatively completed, the design for the T43 called for the upper part of the turret, the gun, and the ammunition-handling equipment to be built as a unit and this unit to be mounted on trunnions on the lower part of the turret. Both parts of the turret were to be traversed together, but only the upper part was to be capable of elevation and depression. The ammunition-handling equipment was to be suspended from or attached to the turret top. The design also called for the use of fixed rounds, to be fed into the gun from a magazine suspended directly behind it.

Because so much had been learned in the attempts to modify the T43 tank's turret for handling fixed 120-mm rounds, little time was required for formulating the military characteristics of the turret for a new 120-mm gun tank to incorporate power ammunition-handling equipment. A project for developing this type of turret was approved in March 1951, and a second project, for development of a 120-mm tank to mount such a turret, was opened in March 1952; the tank to be so developed was designated the T57 120-mm gun tank. It was to be essentially a T43E1 chassis and hull mounting a turret of the oscillating type and a new 120-mm tank gun to fire fixed ammunition. Except for the turret and gun, the principal characteristics of the T57 tank were to be generally similar to those of the T43E1.

In connection with the initiation of work on the T57 tank, a project for the development of the T179 120-mm gun, to be its main armament, was also opened. Designed to have the same ballistic characteristics as the T123E1 gun for the T43E1 tank, it is designed to take the fixed 120-mm ammunition required by the power ammunition-handling equipment of the T57's turret. Five new armor-defeating rounds are being developed for this gun, as follows:

120-mm AP shot, T284
120-mm HEAT shell, T309
120-mm HEP shell, T308
120-mm HE shell, T275
120-mm chemical shell, T276

Engineering tests of the T179 120-mm tank gun-are scheduled for completion by December 1954. Engineering tests of the T57 120-mm gun tank are also to be completed by that time.

TENTATIVE PRINCIPAL CHARACTERISTICS

120-mm Tank Gun, T179

Caliber

120 mm

Length, over-all

no information

Length of bore

60 cal

Travel of projectile in bore

248.3 in

Rifling

no information

Weight of complete gun

6,280 lb

Chamber capacity

1,021 cu in

Density of loading

0.69

Rated maximum chamber pressure

48,000 psi

Breechblock, type

no information

Breech mechanism

no information

Firing mechanism

electric-percussion

Ammunition, type

fixed

Muzzle velocity (AP shot)

3,500 fps

Maximum effective range

2,000 yds

Perforation of homogeneous armor


      AP shot @ 1,000 yd

10.8 in

      AP shot @ 2,000 yd

9.8 in

      HEAT shell @ 0°

16 in

Rate of fire

to be determined

Combination Gun Mount, T169

Weight

no information

Recoil mechanism, type

hydro spring

Number of recoil cylinders

4

Recoil length


      Normal

12 in

      Maximum

14 in

Equilibrator, type

no information

Elevating mechanism, type

electrical and manual

      Maximum elevation

15°

      Maximum depression

-8°

Traversing mechanism, type

electrical and manual

      Maximum traverse, right or left

360°

Fire Control Equipment

(to be determined)

Ammunition Stowage

(to be determined)

Length


      With gun forward

448.375 in

      With gun to rear

397.5 in

Width

144 in

Height

138.625 in

Weight, over-all

117,824 lb

Ground clearance

16.125 in

Tread, from center to center of tracks

115 in

Length of around contact

173.437 in

Ground pressure

12.4 psi

Suspension


      Type

torsion bar

      Wheels

26 in

      Tires

26 x 6 in

Tracks


      Type

steel and rubber

      Width

28 in

      Number of shoes (both tracks)

164

Armor


      Hull


            Type

cast homogeneous

            Front


                  Upper

equivalent to 5 in @ 60°

                  Lower

equivalent to 4.5 in @ 45°

            Side


                  Upper

equivalent to 3 in @ 0°

                  Lower

equivalent to 3 in @ 0°

            Rear

1.5 to 1 in @ 30° to 60°

            Top

1 in

            Floor

0.5 to 1.5 in

      Turret


            Type

cast homogeneous

            Front

equivalent to 5 in @ 60°

            Side

5.375 to 2.75 in @ 20° to 40°

            Rear

1.5 in @ 40°

            Roof

1.5 in

      Gun shield

10 to 4 in @ 45°

Armament


      Main

120-mm tank gun, T179

      Secondary


            Cal .30 machine gun. coaxial (2)

M37

            Cal .50 machine gun, on turret

M2 HB

Communications


      Radios

as selected by Signal Corps

      Interphones (5)

as selected by Signal Corps

Engine


      Type

air-cooled gasoline

      Make and model

Continental AV-1790-7

      Cylinders


            Number

12

            Bore

5.75 in

            Piston stroke

5.75 in

            Piston displacement

1,791.75 cu in

            Arrangement

V-type

      Drive from crankshaft

direct

      Induction system

natural aspiration

      Ignition timing

automatic advance

      Horsepower


            Gross

810 @ 2,800 rpm

            Net

690 @ 2,800 rpm

      Torque


            Gross

1,600 lb-ft @ 2,300 rpm

            Net

1,330 lb-ft @ 2,100 rpm

Electrical system


      Number of batteries

4

Transmission


      Type

CD cross-arive

      Range Selector Control Box


            Type

mechanical

            Linkage to transmission

mechanical

      Torque converter

single-stage polyphase

      Gear shift and steering mechanism


            Internal

hydraulic

            External

mechanical

Oil system


      Capacity

72 qt

      Pumps


            Type

gear

            Number

5

            Drive

2 input and 3 output shafts

Filter, type

air maze, double

Coolant

air

Fuel capacity

230 gal

Brakes


      Service brake, type

wet, multiple disk

      Parking brake, type

lock on service brake

Crew

5

Performance


      Maximum speed on level

22 mph

      Maximum grade climbing ability

60%

      Maximum trench crossing ability

90 in

      Height of obstacles that can be crossed

27 in

      Fording Depth

48 in

      Turning radius

pivot

      Cruising range

80 mi