"To the Chairman of the NKV Technical Council, comrade Satel
To the Chairman of the GAU Artillery Committee, Lieutenant-General comrade Hohlov
To the Head of the NKVD 4th Special Department, Commissar of State Security comrade Kravchenko
October 2nd, 1943
NKV special telegram #5014 sent on September 24th of this year tasked NKV OKB-172 and Molotov factory #172, as instructed by the People's Commissar of Armament and GAU Chief, to produce an SPG with a 122 mm gun that fired a 25 kg shell at 1000 m/s.
Treating this task as high priority, OKB-172 completed this task early, and presents it for your review.
The following was established as a result of completion of the draft project.
- The objective of creating a 122 mm SPG with a muzzle velocity of 1000 m/s is attainable by means of equipping the KV-14 with a new barrel to replace the model 1937 gun-howitzer and using a one-sided hydro-pneumatic balancing mechanism.
- Since the power of SPGs is constantly increasing, you may be interested in the proposal of installation of the OBM-43 gun barrel that fires a 43.5 kg shell at a muzzle velocity of 880 m/s instead of the 122 mm gun with a muzzle velocity of 1000 m/s, as this increases the power of the SPG by 33.5% and improves the effect of the HE and concrete piercing power of the shell.This solution not only introduces a more powerful gun, but uses the same ammunition in the SPG and the towed gun, which significantly improves the production and use of these weapons.
Attached is the comparative data of the KV-1 SPG with the OBM-50 project.
Characteristic | Unit | KV-14 | OBM-50 | |
122 mm gun | 152 mm gun | |||
Caliber | mm | 152.4 | 121.92 | 152.4 |
Shell mass | mm | 43.5 | 25.2 | 43.5 |
Range at 22 degrees elevation | km | 12 | 21 | 18 |
Penetration at 1500 m | ||||
At 0 degrees | mm | - | 195 | 195 |
At 30 degrees | mm | - | 160 | 160 |
Maximum gun elevation | degrees | 22 | 22 | 22 |
Horizontal gun range | degrees | +/- 7 | +/- 7 | +/- 7 |
Ammunition capacity | rounds | 16 | 16 (38 with converted fighting compartment) | 16 |
Rate of fire | RPM | 1.5 | 2 | 1.33 |
Mass of the SPG with gun and ammunition | tons | 47 | 48 | 48 |
Having presented the draft, OKB-172 continues work on the project, which will allow OKB-172 to immediately begin working on blueprints upon receipt of your conclusions.
OKB-172 Chief, Lieutenant-Colonel of State Security, N.A. Ivanov"