A Round Too Long

Historical Overview:

While the T-44 was being developed, there were concerns that the 85mm D-5T wouldn’t be powerful enough to deal with current or future German tanks. Indeed, with increasingly heavier tanks being fielded by the Germans, such as the Panther and Ferdinand, these concerns were validated when trials showed that the 85mm could not penetrate the frontal plate of a Panther at any distance.

Thus the decision was made to fit a 122mm D-25 into the T-44 in February of 1944. This was not the same D-25T as found on the IS and ISU series of tanks however, as the D-25-44 used very long, single-piece ammunition, which had a marginally weaker propellant charge, and lighter recoil elements. Installing the D-25-44 into the experimental T-44s was not a major issue though, as the 1800mm wide turret ring had been designed with more than just the 85mm in mind.

Despite the modifications made to help gunnery and loading, trials were unsuccessful. For one, even with the 1800mm turret ring, the round was still too large to handle efficiently, and the rate of fire dropped to a disappointing 3 RPM. Combined with a meagre capacity of 24 shells, the project for a 122mm armed T-44 was abandoned in the Spring of 1944.

Source(s):
Tank Archives - A Round Too Long
Tank Archives - A Step in the Right Direction