"May 17th, 1945
I report to you on the work performed by the People's Commissariat and factories #92 and #9 on improving the firepower of T-34, T-44, and T-54 medium tanks.
Two types of 100 mm guns were produced for these tanks with turret rings widened to 1700 mm.
- 100 mm LB-1 gun produced at factory #92 (Gorkiy).
- 100 mm D-10T gun incorporating design elements of the D-10S SPG gun produced at factory #9 (Sverdlovsk)
Both guns were installed in turn into a T-34 tank with an expanded turret ring and tested at the Gorohovets proving grounds from April 6th to April 27th. Trials included firing 100 shots and 500 km of driving.
Trials were conducted by a commission appointed by a joint order from the People's Commissar of Armaments, People's Commissar of Tank Production, GAU chief, and commander of Armoured and Mechanized Forces of the Red Army.
Both guns passed trials.
- The 100 mm LB-1 gun passed trials with no significant corrections requested.
- The 100 mm D-10T gun passed trials with some corrections requested, for instance:
- A safety mechanism must be added to the breech.
- A travel lock must be added.
- The relative position of the aiming flywheels and guard rail must be changed to protect the gunner's hands from bruising.
- The extractor must be strengthened.
The following drawbacks were noted that would impact the gun's use in combat.
- There was no lever to manually reset the extractor.
- It is impossible to open the breech manually at a tilt of more than 15 degrees.
- It is inconvenient to load the gun at elevations of over 9 degrees.
These drawbacks and others not mentioned here can be resolved and reworked.
Considering that there are two guns that passed trials, the GAU considers it reasonable to take the following steps:
- If it is necessary to install a 100 mm tank gun into the T-34 tank, then accept the 100 mm LB-1 gun into service.
- If there is a large demand for 100 mm tank guns in the coming months, temporarily accept both the D-10T and LB-1 and time deliveries such that when the demand passes, only the LB-1 remains in production.
- The main factor in deciding the question of improving tank armament is the urgent trials of the T-44 tank with a 100 mm gun, which will be a much better vehicle than the T-34 tank according to preliminary data.
Chief of the GAU, Marshal of Artillery Yakovlev.
To comrades Malyshev, Fedorenko, Korobkov, Ustinov, Petrosyanets, Yakovlev, Kirpichemkov. Present your ideas. L. Beria. May 22nd, 1945"
CAMD RF F.38 Op.11355 D.2732 L.80-81
Printed in Glavnoye Bronetankovoye Upravleniye Lyudi, Sobytiya, Fakty v dokumentakh, 1944-1945 p.499