The Viper Max Shotgun will have two gas pistons. One “Heavy” load (Installed from factory) & One “Light” Load located inside the front part of forearm. The Heavy Load gas piston is recommended for 3.5” shells. The Light Load gas piston is recommended for 2 ¾” & 3” shells. When shooting 2 ¾” shells be sure to have the light load piston installed and have a shell with a minimum of 1 oz @ 1290 FPS or 1 1/8 oz @ 1250 FPS (dram weight 3 1/4). Anything lower will have a varying effect on function. The split ring inside forearm holds the extra gas piston in place. If this ring comes out while removing gas piston, please re-install inside forearm. Installing split ring over magazine tube will cause cycling issues.