A gun (also called a firearm) is a weapon used to shoot one or more metal projectiles called bullets. Guns made of wood or bamboo are thought to have been made in China around 1000 AD. In the next few centuries they spread to other parts of Asia and to Europe where they were made of metal. Guns largely replaced catapults and bows and arrows when they became strong enough to reach out over longer distances to kill or hurt. They are of many different sizes. Some are small enough to hold in one hand. Others are large enough to sink a warship.