"March 12th, 1945
Comments on the use of the SU-100 SPG in combat
- During the fighting of the Corps from January 14th to March 10th, 1945, SU-100 SPGs were used as tanks, as the Corps fought in operative depth and was almost entirely equipped with SU-100 SPGs.
- The off-road mobility of the SU-100 is reduced compared to the T-34 tank, due to the increase in weight and shifting of the center of mass forward due to the longer gun and thickening of the front armour. This adds additional load on the front wheels.
When crossing obstacles off-road, the gun can strike the ground and then the barrel bursts when firing. The gun mount can shift during sudden turns and driving on uneven terrain. There were cases of a complete breakaway of the elevation mechanism. - The crew's work is difficult:
- The crew compartment is smaller due to the larger gun.
- The gun sight is shifted towards the gun (it's uncomfortable for the gunner to aim). It's almost impossible to correct fire with the hatch closed.
- The fighting compartment limits the loader's movement, which affects the rate of fire.
- The average combat rate of fire of the SU-100 is 4-5 RPM. The placement of the ammunition under the gun makes the crew's work difficult.
- The quality of armour is satisfactory, but the quality of welding is not satisfactory. Welding seams burst when the hull is hit.
- The biggest defects of the SU-100 are:
- The elevation mechanism gear teeth can break during firing.
- The oil pipe from the oil filter to the stop valve can break. The causes of the breakages are vibration during movement, thin walls of the pipe, brittle metal.
- Breakage of ball bearings of the front road wheels and layering of the rims due to the shifting of the center of mass and causing additional load.
- Insufficient robustness of the hull welding seams.
- A reduction of fuel capacity by 170 L reduces the range compared to the T-34.
- A lack of machinegun makes fighting infantry difficult, which makes the SPG a poor substitute for tanks.
- The rear plate of the casemate is thin.
- The narrow horizontal traverse angle makes firing at moving targets difficult.
Conclusions:
- The qualities of the SU-100 are superior to that of the SU-85, both the firepower and the technical qualities, but are inferior to that of the tank.
- It is necessary to introduce some design changes:
- Reinforce the ball bearings of the front wheels, since reinforcement of the springs did not have the desired effect.
- Install a new oil pipe for starting up in the winter. Add a carrier in the middle for it.
- Increase the capacity of fuel.
- Reinforce the elevation and turning mechanisms, as well as their carriers.
- Give the commander a machinegun and increase the traverse angle.
- It is reasonable to use the SU-100 as an SPG for escort of tanks, but not as a tank.
Chief of Staff of the 1st Gurds Tank Corps, Guards Major-General of the Tank Forces, Savchenko
Chief of the Operational Department, Guards Lieutenant-Colonel German
March 12th, 1945"