The concept behind the rifled gun follows the rule of "everything is better with spinning". If a bullet spins (usually at many thousands revolutions per second), its accuracy and range is greatly enhanced. This is achieved by reshaping the barrel by cutting a helical groove, or a pattern of grooves, into the barrel walls. Origins of a rifled gun (later called a rifle) are lost to antiquity, but are probably as old as the 15th century. Limitations of muzzle-loading and black powder greatly hampered the potential of the early rifled guns, as they were much slower to reload than smoothbore muskets, and therefore limited to specialists. This all changed rapidly with the invention of the Minie bullets in 1840. Those bullets expanded during the shot, so they were both easy to load and clang closely to the barrel walls after expanding, which increased the range sixfold as compared to contemporary muskets (and accounted for the extreme body count of the American Civil War). This started a rapid revolution of rifles. By the 1890's, they featured bolt-action breech-loading systems, made possible by the earlier invention of integrated cartriges (which featured a bullet and propellant in one metal casing), new smaller cartriges (made possible with Cordite, which was much more powerful and cleaner than black gunpowder), and box magazines that increased fire rate even further. By that time, rifles were capable of firing at ranges in exceed of 1 km and fire rate exceeding 30 shots per minute, and were considered a pinnacle of technology in personal weaponry - especially considering the huge gap between them and the muskets that were universally used just 50-60 years before.