P.O. Ackley

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.
Biography.
Ackley began gunsmithing full-time in Oregon in 1936, but was interrupted by World War II. In 1945, he established a new shop in Trinidad, Colorado, and soon became one of the largest custom gunmakers in the United States. He was also on the staff of the magazines "Guns&Ammo" and "Shooting Times", and was an instructor at the Trinidad State Junior College from 1946 to 1951, where he did much experimentation in the field of firearms. For a complete biography read the book, "P.O. Ackley, America's Gunsmith" .
Wildcats and Ackley Improved Cartridges.
The following is a list of Ackley cartridges, both "Improved" versions (requiring only fireforming) and more complex versions involving case length reductions or caliber changes. In addition to being easy to form, firearms chambered for the "Improved" cartridges could fire standard factory loaded ammunition as well, allowing a shooter to use commonly available ammunition if the wildcat loads weren't available.
Other Research.
Ackley was not just a wildcatter, he was a researcher as well, often testing firearms to destruction in the search for information. He also produced a number of experimental cartridges, not intended to be practical, but rather to test the limits of firearms. One of these experimental cartridges was the .22 Eargesplitten Loudenboomer. This humorously named cartridge was developed by Ackley for Bob Hutton of "Guns & Ammo" magazine, and was intended solely to exceed muzzle velocity. Ackley's loads only managed (Mach 4.2), firing a bullet. Based on a .378 Weatherby Magnum case, the case is impractically over-capacity for the bore diameter, and so the cartridge remains a curiosity. The advent of new slower-burning smokeless powders may have changed the equation.
Another humorous round, the .17 Flintstone Super Eyebunger, based on the .22-250 necked down to .17 caliber, has been used by Australian gunsmith Bill Hambly-Clark, Jr. to achieve velocities of out of a barreled gun.
NOTE:
The term "Ackley Improved" has been applied by various gunsmiths conceptually to many cartridges not extant during P.O. Ackley's lifetime. 
By P.O. Ackley's definition of Improved, a firearm so chambered must be capable of shooting the factory original round, also such cartridge case either necked up or down to a different bullet size, without stretching the case. To accomplish this, the chamber for a rimless bottle necked "improved" cartridge must be somewhat shorter in the body than the original so that there is no headspace when the round is chambered.