The Hellstorm is a tiny spring loaded device that clamps to the trigger guard to provide simulated automatic fire. It is easy to install, requiring only a screwdriver to attach. For operation, simply hold the gun loosely with your non-trigger hand and hold the trigger finger stiffly.
When firing commences the weapon will recoil and the device is pressed against the trigger. The tension arm in the device causes the gun to move forward again, causing the trigger to be pressed against the trigger finger again. The system utilizes the gun's own recoil and inertia.