SU-122 Requirements

 "Approved by Deputy People's Commissar of Defense, Colonel General of Artillery, Voronov

October 17th, 1942

Tactical-technical requirements of a 122 mm self propelled howitzer on the chassis of the T-34 tank

1. Purpose of the self propelled howitzer

The self propelled howitzer is designed to accompany infantry and tank units, destroying dugouts and fortified firing positions with direct fire from short range or with indirect fire.

2. Requirements for the artillery component

The artillery component of the SPG is provided by the stock rotating part of the M-30 122 mm model 1938 howitzer. The mounting must meet the following requirements:

1. Practical rate of fire of no less than 10 RPM in a direct fire role.
2. Elevation of 25-35 degrees.
   
3. Depression of -3 degrees.
4. Traverse of +/- 10 degrees.
5. The recoil buffer must be armoured. The armour must be at least 12 mm thick.
6. The oscillating part of the howitzer with the recoil buffer armour must be completely balanced. Increase in effort required to aim cannot surpass 10%.
7. The height of the bore axis must be no more than 1500 mm. To achieve this, a cutout in the front of the SPG is permitted.
8. The gun port must be completely covered at a gun elevation of up to 12 degrees.
9. The gun mount must allow for comfortable loading at all angles of elevation and traverse.
10. The sight is the stock sight from the 122 mm M-30 howitzer with a Hertz panoramic sight.
11. The gunner's seat must rotate with the gun. The seat's rotation in relation to the panoramic sight and aiming flywheels must allow for comfortable operation.
12. The crew consists of five men, including the driver. All crewmen must have comfortable seats.
13. The gun must have the ability to be reliably fixed for travel, preventing horizontal and vertical movement.
14. Two PPSh submachine guns must be carried as auxiliary armament.

3. Requirements for the chassis

The chassis of the T-34 medium tank must be used. Upon installation of the 122 mm howitzer, the following changes are permitted.

1. Changing the angle of the sides in order to create a roomy fighting compartment.
2. A cutout in the front plate to allow for the gun to be mounted at the required height.
3. Moving fuel tanks out of the fighting compartment. It is permissible to move them to the radio operator's station.
4. Moving the driver's seat and all his mechanisms up to 200 mm to the left. Changes to the engine group layout and transmission components are not allowed.

The 122 mm self propelled howitzer must meet the following requirements:

1. The full travel weight must not exceed the mass of a production T-34 tank (28.5-29 tons).
2. The height during travel must not exceed 2000 mm.
3. The top speed at the highest gear on a good road must be 47 kph.
4. The SPG must remain stable when firing tilted, facing downhill, or facing uphill, at all traverse and elevation angles. The gun has to be operational both from standstill and on the move.
5. The gun mount is armoured. The armour must protect the gun, its crew, fuel tanks, and ammunition from all sides. The crew exits the vehicle from the rear, through a hatch that flips out.
   Required armour thickness:
   Front: up to 90 mm.
   Side: 45 mm
   Roof: 20 mm
6. The armour of the SPG must guarantee:
1. Protection of the gun and its crew.
2. Rapid entry and exit.
7. The performance, off-road mobility, and cruising range must be the same as those of a T-34 tank.
8. The SPG must carry the following in special racks:
1. No fewer than 40 rounds for the gun and 1500 rounds for PPSh submachine guns. The ammunition must be stored in places where it is easy for the loader and breech operator to reach it, must be securely fastened in its slots, and easy to unfasten in order to retrieve.
2. Pioneer tools: an axe, a saw, a crowbar, a shovel.
3. Tools and parts for the artillery component.
4. A first aid kit and rations for the crew.
9. The communications must be provided by:
1. 9-R radio for external communication.
2. TPU-3 intercom for internal communication.
10. Include the following in the fighting compartment walls:
1. Observation ports to observe the battlefield with adjustable heights.
2. Ports for firing the PPSh SMG.

GAU Chief, Colonel General of Artillery, Yakovlev"

RGASPI F.644 Op.2 D.103 L.142-143