Advances in aircraft survivability thanks to all-metal construction and self-sealing and inert gas-filled fuel tanks led to experimentation with large-caliber weapons to shoot them down.

In Soviet Union, Leonid Kurchevsky developed a series of recoilless rifles in various calibers and in 1930 was decided to adapt the 76.2 mm (3 in) weapons for aircraft use.

A single small-caliber synchronized machine gun in the left fuselage was added to aid the pilot in aiming.

By the time this last batch was being delivered, however, it was already apparent that the concept of a "single-shot" fighter was flawed and the I-Zs that had been built were relegated to various testing roles.

[1] Data from Istoriia konstruktskii samoletov v SSSR do 1938 [1]General characteristics Performance Armament