Parker Otto Ackley (May 25, 1903, Granville, New York – August 23, 1989) was an American gunsmith, barrel maker, author, columnist, and wildcat cartridge developer. The Ackley Improved family of wildcat cartridges are designed to be easily made by rechambering existing firearms, and fireforming the ammunition to decrease body taper and increase shoulder angle, resulting in a higher case capacity. Ackley improved not only standard cartridges, but also other popular wildcats, and was the first to create a .17 caliber (4.5 mm) centerfire cartridge.