S-51 Heavy SPG

The S-51 was an experimental heavy self-propelled gun designed by TsAKB.

At the end of 1942, the Red Army switched from defensive to offensive operations which revealed the need for self-propelled artillery. Against pillboxes and fortified buildings in urban battles, the firepower of towed and self-propelled artillery of 152.4mm caliber was sometimes not enough. To solve this issue, the Red Army was armed with the towed 203 mm howitzer M1931 (B-4). However, the 203 mm howitzer was unarmoured which makes attacking risky and had low speed which made swift breakthrough of enemy lines impossible.

Therefore, the Red Army initiated a project for a heavy self-propelled gun. Plant № 100, CB Uralmash, and TsAKB took part in this competition. Plant № 100 under the leadership of Josef Yakovlevich Kotin created a self-propelled gun carriage that looks similar to the Canon de 194 mle GPF. The design by CB Uralmash was two 152mm howitzers on two connected SU-122 chassis.

In the autumn of 1943, the TsAKB designed and built a self-propelled gun on the basis of the KV-1S equipped with the 203mm howitzer. The self-propelled gun received the designation, S-51.