the grigorovich i-z was a fighter aircraft developed in the soviet union during the 1930s. 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.