Monday, 3 February 2014

KV-7 Guns

The origins of the KV-7, an SPG on the KV-1 chassis with multiple guns, began in November of 1941 at the Kirov factory, after evacuation to Chelyabinsk.

CAMD RF 81-12104-79

"November 25th, 1941
According to the personal decree of the People's Commissar of Defense, comrade Stalin, the Kirov factory (city of Chelyabinsk, ChTZ) is developing a gun mount for the KV tank (two 45 mm tank guns and one F-34 76 mm tank gun). 
In order to develop these mounts, four 45 mm tank guns are needed urgently. 
In order to mass produce KV tanks with multiple guns, 180 45 mm guns with breeches should be delivered to the Kirov factory in December of 1941, and 260 in January of 1942, without the mount, recoil brakes, semi-automatic devices, and sights."

90 KV-7s in December was a very liberal estimate. The KV-7 only began trials in December, with disappointing results.

CAMD RF 38-11355-668

"[day cut off] December, 1942
The KV-7 gun mount that underwent trials on December 27th, 1941, requires correction of defects and urgent proving grounds trials.
Without performing trials, the mount cannot be equipped with proper sights. The installed TMFD-8 sight merely marks the place where a sight would be placed, and must be altered for use, specifically with new markings. Furthermore, attachment of the sight at only one point is undesirable.
The robustness trials performed at the Kirov factory were only done with stock combat rounds. Testing rounds were not used. No measurement of parts was performed. The parts must be tested with increased strength rounds.
The turning mechanism of this system, screw type with two ball and socket joints, is of suboptimal design, and results in high dispersion during firing. This mechanism will require constant maintenance and observation, as wear on the balls will reduce precision and accuracy.
A redesign of the turning mechanism is desirable. A sector type mechanism is preferable. Install limiters on turning and elevation mechanisms. The brass catcher needs a redesign. Lengthen the left and right cheeks by at least half of the length of the breech, otherwise the crew is not protected from the guns' recoil. The overall width of the catcher can be reduced, but the height of the walls must be increased. 
Change the position of the forehead rest. It is inconveniently located, and the gunner cannot use it.
The firing mechanism pedal needs to be moved. Its location prevents placing 76 mm shells in cassettes.
The gunner's seat needs to change, most notably the back should be curved.
At maximum depression angles, the recoiling guns can break the ceiling lamp. Design the compartment in such a way that the recoil indicator gauges are illuminated.
Connect the driver and gunner with a communication device, as rough aiming is done by turning the tank."

However, only a few days later, Stalin made a decision to change the armament. 
"On production of KV-7 and KV-8 tanks
  1. Stop work on the 3-gun KV-7.
  2. Equip the KV-7 with two 76 mm guns with +/- 7.5 degrees of horizontal range, +15 degrees of gun elevation, and -5 degrees of gun depression.
  3. ..."
RGASPI 664-2-32

Work on this new tank also took a long time.

"The KV-7 tank was completed on May 11th, 1942, and trialled on the 14th at the Kopeisk proving grounds. 17 shells were fired, of those 5 were single shots and 12 in salvo. The target was 1.5 by 1.5 meters, 800 meters away. As a result of this data, the following conclusions can be made:
  1. The precision and accuracy when firing from the spot is good with the paired gun system. After calibration, 11 shells landed in an ellipse with the larger diameter 40 cm in length, and smaller diameter 13 cm in length. 
  2. The rate of fire is 6-7 salvos per minute. Due to the unbalanced system and non-self-braking elevation mechanism (like the sector-type elevation mechanism) installed, the elevation increases after firing by 25 thousandths.
  3. The turning mechanism is heavy, and needs to be turned with both hands, which is unacceptable.
  4. The shell cassettes in the turret bay cause difficulty when working and must be replaced with an open type ammunition rack.
  5. The firing mechanism is too heavy when firing in salvo, and should be lightened by a factor of at least two.
  6. There is no mechanism for artificial recoil, which would also need a hatch in the rear. That hatch should also be usable for crew evacuation. 
I ask for further instructions on this gun system."
CAMD RF 38-11355-639

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