Automatic cannons are artillery pieces designed to fire shells at a high rate without the need for manual reloading after each shot. They use a mechanism that automatically feeds ammunition into the chamber, allowing for rapid firing, which is particularly useful in combat situations. These cannons can be mounted on various platforms, including vehicles and ships, enhancing their mobility and effectiveness. Typically, automatic cannons are classified by their caliber, with common sizes ranging from 20mm to 40mm. They are often used in military applications for air defense and ground support, providing a powerful means to engage enemy forces or incoming threats, such as aircraft or missiles.