The Gardner machine gun was invented in 1874 by William Gardner of Toledo, Ohio formerly a captain in the Union army during the American Civil War. After producing a prototype he went to the Pratt and Whitney company, who after a year of development produced a military version of the weapon. Parkhurst added many improvements to the gun's firing mechanism which made it more reliable. During 1877 additional tests took place with a .45 calibre (11.4 mm) version of the weapon, which determined its muzzle velocity to be 1,280 feet per second (390 m/s).