Monday, 18 August 2014

Upgunning the T-60

"To the chief of the GABTU Armour Directorate, Brigade Engineer Korobkov

Report on the issue of rearming the T-60 with a 45 mm model 1938 gun

The 20 mm ShVAK gun installed on the T-60 showed itself lacking in combat conditions (it is hard to manufacture, hard to study, demanding on the battlefield, lacks interchangeable parts, etc). The Molotov GAZ factory is developing a project to install a 45 mm tank gun and a DT machinegun into a T-60 turret, while maintaining the 900 mm turret ring and turret size.

The gun position is as follows (see diagram #1).


The 45 mm tank gun is shifted to the right. Next to it is the DT machinegun, and left of that is the TMFP sight. The gun is loaded by one person, and it is only possible to fire from either the gun or the machinegun. 

The shells and machinegun disks are stored on the walls and the floor. The ammunition capacity is not yet determined. The turning mechanism is to the right, the elevation mechanism is to the left. The triggers are buttons, both for the gun and machinegun. 

Second project: Factory #92

Retaining the size and turret ring of the current turret, the T-60 is armed with a 45 mm gun, DT machinegun, and TMFP sight. The placement in the turret is as follows (see diagram #2):


The 45 mm gun is shifted to the right of the center, and the DT machinegun is shifted to the left. The gun is serviced by one person (tank commander). His seat is positioned in the rear of the turret, between the gun and machinegun. The trigger for the gun is placed on the handle of the turning mechanism, and the trigger for the machinegun on the handle of the elevation mechanism. 

Factory #92 has blueprints for the mount, and has begun assembly on December 20th, when they received a T-60 tank. 

Molotov factory (comrade Astrov) does not have blueprints, but they have a prototype, although it is imperfect and unfinished.

Drawbacks of both projects:
  1. The turret with a 45 mm gun is unbalanced, as a result of which, turning is difficult.
  2. Servicing the gun alone (loading, observation of the battlefield, aiming, etc) reduces the rate of fire of the gun. The gunner must lose sight of the target after he fires to load, and then re-acquire the target every time.
  3. In order to access the turning mechanism while sitting, the gunner must put his hand under the gun, which is uncomfortable.
  4. The brass catcher needs a 30 kg weight to balance the 45 mm gun.
  5. The recoil resistance (R=3500 kg) acts on the turret ring gears and strikes the turning mechanism, since the gun is off center.
  6. The fighting compartment is cramped and uncomfortable.
Advantages of the projects:
  1. The tank's firepower is increased. The penetration and range are increased. The tanks are easier to supply with ammunition.
  2. The 45 mm gun is already in use in the Red Army. It is reliable and easy to produce.
Having weighed the advantages and drawbacks of both projects, a final conclusion is only possible after trials. Propose to GAZ and factory #92 that they should have the prototypes produced in metal by January 15th, 1942, and perform trials on January 25th, 1942, so that the drawbacks can be evaluated. 

Personally, I consider the GAZ modification superior. I think it is necessary to order a new turret (cast) with a turret ring that is 25-30 mm wider for trials on January 25th. The automotive factory already has a project for a cast turret (see diagram #3).


Until the issue of the 45 mm gun is resolved, the turret will contain a DT and a ShVAK or a DShK. As the 45 mm gun is large for the current T-60 turret, aim for the new 37 mm gun designed by factory #92. Experimental prototypes of the gun will be ready for January 15th, 1942.

Data on the 37 mm gun: 
  • Mass: 170 kg
  • Ammunition: 37 mm AA gun shell
  • q: 0.72 kg
  • λ: 170 mm
  • Maximum pressure: 2800 kg/cm^2
  • Length: 2315 mm
  • Energy: 30,724 ton-meters
  • R=513 kg
  • Recoil brake: hydraulic
  • Return mechanism: sprint, in one cylinder
  • Penetration at 0 degrees (according to the Jacob de Marre formula):
    • 100 meters: 54.65 mm
    • 500 meters: 45.8 mm
    • 1000 meters: 35.8 mm
It is reasonable to ask factory #92 to accelerate the production of this gun and test it on the T-60 by February 1st, 1942.

Military Engineer 1st class, N. Ogurtsov
December 30th, 1941"


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