SU-100Y - The Soviet "Boxtank"

While fighting the Winter War against Finland, the Soviets started the development of a bunker-busting self-propelled gun named the SU-100Y. It was created by placing a powerful 130 mm naval gun on the chassis of the T-100 heavy tank.

Though technically designed to eradicate fortifications, the SU-100Y would have made light work of any German tank unfortunate enough to find itself in its sights.

Its an extremely simple design, with flat sided armor, no machine guns and it doesn’t even have hatches for the crew.

By the time the SU-100Y was complete the Winter War had ended and the Soviets had little use for this 60 ton beast. However the single SU-100Y built was reportedly pulled out of storage and used to help defend Moscow in 1941.

Developing the SU-100Y

Experiences in the ongoing Winter War showed that there was a need for a tank capable of destroying fixed fortifications and concrete bunkers. A requirement was made for a vehicle containing a 152 or 203 mm bunker-busting gun.

The T-100X had been ordered by the Soviet Ministry of Defense in early January 1940, but designers at Factory N°185 bravely decided to build a dedicated self propelled gun named the T-100Y (also known as the SU-100Y) instead.

The SU-100Y

The SU-100Y was built on the hull of the second T-100 prototype. The T-100’s turrets and associated systems were removed and replaced with a 130 mm B-13 high-velocity gun.

This gun was extremely powerful, especially for the time. Originally a Navy weapon – used on cruisers and in coastal batteries – the gun was overkill against most armored vehicles the Soviets would face during the war.

The SU-100Y had a pretty unusual crew arrangement, with a driver, radio operator, two loaders, a commander and a gunner.

Somewhat strange is the SU-100Y’s lack of roof hatches on top of the casemate, which likely severely limited the crew’s quality of life and situational awareness. The crew would have entered and exited the fighting compartment via a door at the rear of the casemate.

Fate

The end of the Winter War and its lengthy procurement process meant the SU-100Y was not ordered into production. The sole example was moved to the Kubinka proving grounds in mid 1940.

From here the story gets a little hazy. There is a common belief that in late 1941 the SU-100Y was brought into Moscow to defend the city against the Germans.

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