The Gatling gun has had a rather unusual history. Although originally from North Carolina, Gatling moved to Indiana in order to develop his design, and does not seem to have thought of going back to his roots, when the Civil War broke out. . He strongly marketed it to the US government to help put down the Confederate "rebellion" , and sold a number of them. But they saw, and would see, little use in the US. At first, almost certainly because the design of the gun was far more advanced than the design of the ammunition it was supposed to use, but after 1865 simply because the US didn't get into a major war for quite some time. Although there were a few Gatling guns apparently deployed in the New York draft riots of 1863, it seems unlikely they ever fired on the rioters, did more than intimidate.

Most of the sales of the Gatling gun in the next 20 years were instead to foreign countries. notably Britain, Spain and Russia. Once the ammunition problem had been solved, they were found to be extremely reliable. They performed better than the other battery-guns on the market, like the Mitrailleuse , that were made to be more of an odd cannon and part of the artillery, not a part of the infantry. And the Nordenfelt and Gardner were not quite as reliable. Gatling guns became very useful. Most of the European powers were fighting colonial wars in this period. The typical expeditionary force would be rather small compared to the large native one it would face, and the Gatling gun turned out to be important as an "equalizer", and made the colonial invaders far more successful. Just as there was little doubt expressed by the general public over the morality or justice of colonialism, there seems to have been little doubt about the morality or justice of using the Gatling gun against comparatively poorly-armed Africans. When Britain decided to grab the Ashanti kingdom in west Africa, in 1873, the London Times urged that British soldiers "treat the Ashanti to a little Gatling music".

However, the decades after the US Civil War saw a great deal of modernization of all military weaponry in general, and great advances as well in the scale of military manufacturing. Rifles went from black-powder single-shot guns to smokeless powder magazine weapons, cannon became breech-loading. Like most 1860's weaponry, Gatling's gun became outdated: he had the most successful machine gun in the 1870's, when he only got competition from the Mitrailleuse, Nordernfelt and Gardner. But like those, his gun had to be cranked. After 1882 , when Hiram Maxim patented a machine gun that would reload itself, the Gatling gun fairly quickly was displaced. But the Europeans' increasingly lethal weapons, deployed against weak opposition, had fostered a smug sense of technological and racial superiority among them. That smug superiority would be greatly damaged in WWI. When they would finally use their lethal weapons against each other they would discover that their own deaths could also be produced in industrial quantities.

The Gatling gun would play little, if any part in WWI, or WWII. But the most unusual thing about the story of the Gatling gun was that, unlike all of its contemporaries, it was revived. In 1945 it was discovered that , powered by an electric motor, the gun could have an enormous rate of fire, up to around 7,000 rounds a minute. Re-named the Vulcan gun, it has since has been widely adapted, with sizes ranging from small caliber to cannon. For industrial production of death and destruction, Gatling's gun seems quite competitive once again.