The idea of multi-barreled artillery systems that could fire a salvo occupied the minds of tank designers from many countries. In one case, a design made it to mass production and even to battle: the light Marmon-Herrington MTLS-IGI4, armed with two 37 mm guns. 145 tanks were built, used in combat in the Pacific.
In the USSR, the most famous multi-barreled tank was the KV-7.An experimental prototype of the assault tank (it was never called an SPG) was designed in November of 1941 in Chelyabinsk on Stalin's orders. The KV-7 was armed with two 45 mm guns and one 76 mm ZiS-5 gun. The KV-7 could fire all three guns at the same time. A prototype was finished in December of 1941, and mass production was expected. Archive data reveals that KV-7 hulls were ordered before trials even began, and 20 of them were made. Trials in January of 1942 showed the poor execution of the simultaneous firing idea. The KV-7 was converted to use a pair of 76 mm guns, but the results were largely the same.
While the KV-7 was being worked on, a project on the T-34 chassis was developed in Nizhniy Tagil at factory #183. The tank, indexed T-34-3, had two 45 mm guns and one 76 mm gun in a rotating turret. Unlike the KV-7, this tank did not make it to metal. Activity on this topic ceased, but not for long.
In the middle of December of 1942, the Technical Council of the People's Commissariat of Armament composed tactical-technical characteristics for an SPG with two 122 mm M-30 howitzers. This request was a project of personal initiative, since it did not receive high priority. It was proposed by Major-General of the Artillery Engineering service, A.A. Tolochkov, who was the chief of the experimental designs department. The requirements were as follows:
- The armament must consist of two 122 mm howitzers, using barrels and breeches from the M-30.
- The guns must have the same mount, but have separate recoil brakes, as similar as possible to those on the M-30.
- The mount and recoil mechanisms must be protected by armour.
- The vertical traverse must be from -5 degrees to +15 degrees, horizontal traverse of 15-20 degrees.
- The front armour must be 70 mm thick, side armour 30 mm, roof and rear 15-20 mm.
- T-34 components must be used as much as possible.
- The ground pressure must not exceed that of the T-34.
- The guns must be able to fire individually or simultaneously.
- 1 or 2 additional DT machineguns must be available as additional armament.