Sunday, 29 March 2015

Autoloaded IS-3 Short History

In mid-50’s, a part of the Soviet army was having a look at their heavy tanks, analyzing their issues and drawbacks. One of the major issues of the heavies was their low rate of fire. The two-piece shells were quite slow to load, resulting in average rates of fire somewhere between 2 and 3 rounds per minute (compared to 6 to 8 rounds per minute of the medium tanks). This was especially true for the 122mm shells of the D-25 gun and ways were sought to remedy the situation.

One of the solutions that presented itself during the research was to equip tanks armed with 122mm D-25 with some sort of automatic or semi-automatic loading system. The system however was quite unwieldy and since the loader still had to be present and the turret was not big enough, such a system could potentially lead to the reduction of the amount of ammunition carried.

The use of the electro-mechanic rammer on the T-10 made the life of the loader much easier and it had other advantages as well – the gun could be for example loaded while elevated up to 28 degrees – but failed to significantly increase the tank’s rate of fire – with the two-piece ammunition, it stayed relatively low (4 rounds per minute).

To improve the rate of fire, the students of the BTV academy (Military Armored Forces Academy) came with a novel solution – to install 2 two-layer pistol-style magazines into various heavy tanks, including the IS-3.  The magazines served as ammo racks (they were not loaded extra) and were operated electrically (using hydraulics).  One magazine contained HE shells, one contained AP shells.  In case of electric (hydraulic) failure, the magazines could be also operated manually. In order to fit the entire magazine into the turret, the inside had to be significantly reworked and the tank crew was according to the BTV proposal to be reduced to three men, the design of the turret had to be changed somewhat as well. Additionally, since less recoil was required to make the project functional, the gun recoil compensator mechanism would also have to be changed.

This project was however never accepted by the military and was basically just a thought exercise.  Further research focused on creating a proposal for the automatic loading of the 122mm M-62 gun on the T-10 tank.