The machine gun developed gradually through the 19th century. Early work focused on multi-barrel guns, such as the Gatling gun invented by Richard Gatling in 1862. However, these guns remained prone to jams due to their reliance on black powder and gravity feeds. The first true machine guns waited for the development of smokeless powder and metallic cartridges. With these, Hiram Maxim built a single barrel gun in the 1880s that used the force of one shot to discharge, reload, and to fire again. The Maxim, fed with a fabric belt of bullets, could fire indefinitely.