M-109 self-propelled artillery firing a load. Self-propelled artillery (also called locomotive artillery) is artillery equipped with its own propulsion system to move toward its firing position. Within the terminology are the self-propelled gun, self-propelled howitzer, self-propelled mortar, and rocket artillery. They are high mobility vehicles, usually based on continuous tracks carrying either a large field gun, howitzer, mortar, or some form of rocket/missile launcher. They are usually used for long-range indirect bombardment support on the battlefield.