- In August of this year, factory #92, while mounting the F-34 gun on the KV-1, reinforced the gun mount as a result of having to move the trunnions in order to balance the gun (which takes as much effort as making a new mount).
- The resulting 76.2 mm caliber gun is called "ZiS-5" by the factory, and is preferable for installation in the KV-1 tank for the following reasons:
- The mount is sturdier, with 15 mm walls instead of 8 mm.
- The button firing mechanism is made according to the Artkom GAU KA journals, and is superior in performance.
- A T-900 4x sight is used instead of a 2.5x sight, in order to reduce the opening in the gun mantlet.
- The muzzle velocity of the armour piercing shell can be increased to 780 m/s with a special charge, which increases penetration to 75 mm at 1000 meters.
- Factory #92 received an order from Moscow to cease manufacturing of prototypes, despite the fact that parts for 25 prototypes have already been produced.
- Since the Kirov factory has stopped supplying ChTZ with F-32 guns as of August this year, ChTZ was ordered to install the F-34 gun on the KV-1, with all required mount trunnion changes. In order to assist in this, one engineer from factory #92 was sent to ChTZ by airplane with one F-34 gun, and later, 16 more F-34 guns were sent by rail. If necessary, factory #92 can send more of its employees.
- It will take as much time to adapt the F-34 gun to the KV-1 as it would take to produce the ZiS-5 gun.
- No additional equipment is required to produce the ZiS-5 gun. Required tools have already been ordered by the factory. The factory has necessary blueprints and instruments.
- Factory #92 can start manufacturing ZiS-5 guns at the cost of removing other guns from production, such as the F-34.
- Major-General comrade Grabin made it clear that he can produce 20-25 ZiS-5 guns in excess of the factory's quota.
- Major-General comrade Grabin stated that all he saw on the issue of producing the ZiS-5 is talk, and despite its advantages, there is no singular decision. If this continues, he will have to write to Stalin personally.
CAMD RF 38-11355-148
Letters to Stalin or not, but the ZiS-5 gun made it into mass production for the KV-1. The special AP shell, on the other hand, didn't, as every source that I have read gives identical ballistics for the F-34 and ZiS-5.