Agar gun The Agar gun was an early rapid fire machine gun developed during the US Civil War . The spelling Ager is sometimes used . The weapon was nicknamed the Coffee Mill Gun and was also called the Union Repeating Gun . History . During the Civil War , inventors were encouraged to create new and better weapons . The Agar machine gun was one of about a dozen or so hand - cranked machine guns developed for the war during this period . It was named after its inventor , Wilson Agar ( sometimes spelled Wilson Ager ) . The gun was nicknamed the ' Coffee Mill Gun ' because the crank and the ammunition hopper on the top of the weapon gave it a look similar to that of a common kitchen coffee grinder . Agar advertised the gun as " an army in six feet square " , due to its high rate of fire . In 1861 , the Agar machine gun was demonstrated to President Abraham Lincoln , who was very impressed by the weapon . Lincoln wrote " I saw this gun myself , and witnessed some experiments with it , and I really think it worth the attention of the Government . " Ten of the weapons were purchased immediately . The Union eventually ordered fifty four additional machine guns . Despite their potential , these weapons saw little use during the war , and were sold after the war ended . Design and Features . The Agar machine gun fired . 58 caliber cartridges . Standard paper cartridges were loaded into re - usable metal tubes . A separate percussion cap was fitted to a nipple at the rear of this tube , and the loaded tubes were placed into a funnel shaped hopper , which gave the weapon its " coffee mill " appearance . The weapon was fired using a hand crank , located at the rear of the gun . The crank would feed rounds into the weapon from the hopper , and would fire them one by one . A wedge shaped block would rise up and lock the round in place , a cam operated hammer would then strike the percussion cap , firing the round . The empty metal tubes would subsequently be collected in a pan located under the weapon . The metal tubes would then be reloaded and placed back in the hopper . This made quite a bit of work for the gun crews , since the tubes had to be reloaded quickly enough to keep up with the machine gun ' s relatively high rate of fire . The Agar machine gun had a single barrel . This design proved to be vulnerable to overheating , especially during periods of sustained fire . The overheating problem was solved somewhat through the use of replacement barrels which could be swapped when the barrel in use overheated . Two spare barrels were typically carried with each gun . Agar also added a cooling mechanism to the barrel , which consisted of a metal jacket through which air was forced to provide cooling . The air came from a turbine , which was powered by the same hand crank that was used to fire the weapon . This cooling air also tended to blow away any pieces of unburned paper from the cartridge that happened to be near the barrel . The rate of fire was also limited to 120 rounds per minute , which helped to prevent overheating . The Agar gun can thus be classified as a multiple - chamber , single - barrel design . In this classification scheme , it is in the same category as the much better known revolver cannon s , still in use today . The Agar gun ' s hopper is in fact the only multiple - chamber configuration other than the ubiquitous revolver to have been used in practice . The Agar machine gun also had a built - in steel shield , which was a design feature not seen on other machine guns of the period . This gave the Agar a much more modern appearance , since single barrel machine guns with similar shields became common in World War I . Use . In 1861 , the Agar machine gun was demonstrated to President Abraham Lincoln , who was so impressed that he ordered all ten available weapons to be purchased immediately , at a cost of $ 1 , 300 each , which was a very high price at the time . Later in the same year , General McClellan ordered an additional fifty weapons , at a reduced cost of $ 735 each . In 1861 , General Butler purchased two guns at $ 1 , 300 each , and in the following year General Fremont also purchased two guns , paying $ 1 , 500 for each . The guns were condemned by the Ordnance Department for using too much ammunition to ever be practical , and the guns saw little use on the battlefield . They were often deployed to remote locations to guard bridges and narrow passes . The guns often performed poorly in the field . The single barrel design proved vulnerable to overheating , and the weapon was also prone to jamming . The special steel tubes used to hold the cartridges were heavy and expensive , and were often prone to loss . Later cartridges would use brass , but this was not widely available during the time that the Agar machine gun was used . The gun ' s range was also criticized . It had a range of about 800 yards , which was roughly the same as the range of the rifle - muskets used by infantry . A longer range weapon would have been preferred . Because of the way it was used in battle , the Agar machine gun , like most machine guns of the period , was never able to show its potential . Machine guns would later become much more important on the battlefield . In 1865 , the few remaining Agar machine guns were sold for $ 500 each .