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Parker Otto Ackley
File:P.O. Ackley.jpg
Born (1903-05-25)May 25, 1903
Granville, New York
Died August 23, 1989(1989-08-23) (aged 86)
Salt Lake City, Utah
Nationality United States
Occupation gunsmith, author
Known for Ammunition designer

Parker Otto Ackley (May 25, 1903, Granville, New York – August 23, 1989)[1] was a prolific gunsmith, 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.[2]


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.[3]

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.[4][5]

  • .17 Ackley Hornet, a .22 Ackley Hornet necked down to .17 caliber (4.5 mm)
  • .17 Ackley Bee, a .218 Improved Bee necked down to .17 caliber (4.5 mm)
  • .22 Ackley Improved Hornet, an improved .22 Hornet
  • .218 Ackley Improved Bee, an improved .218 Bee
  • .219 Zipper Improved, an improved .219 Zipper
  • .22/.30-30 Ackley Improved, a .30-30 Ackley Improved necked down to .22 caliber (5.56 mm)
  • .22-250 Ackley Improved, an improved .22-250 Remington
  • .223 Ackley Improved, an improved .223 Remington[6]
  • .224 Belted Express, formed from .30-06 Brass; very few die sets were made by RCBS
  • .228 Ackley Magnum, an improved 7x57mm Mauser necked down to .228 caliber (5.8 mm); bullets in this size are hard to find but provide greater weight than .223 caliber bullets, up to 100 grains (6.5g), without excessively quick twist rate.
  • 6 mm/.30-30 Improved, a .30-30 Ackley Improved necked down to 6 mm (.243)
  • .243 Ackley Improved, an improved .243 Winchester
  • .25 Ackley Krag, a .30-40 Krag necked down to .25 caliber (6.2 mm)
  • .25-06 Ackley improved, an improved .25-06 Remington with a 40 degree angled shoulder
  • .25 Ackley Krag Short, a slightly shortened .25 Ackley Krag
  • .250-3000 Ackley Improved, an improved .250-3000 Savage
  • .257 Ackley Improved, an improved .257 Roberts
  • 270 Winchester Ackley Improved, an improved .270 Winchester[7]
  • .280 Remington Ackley Improved, an improved version of the 280 Remington cartridge with 40 degree shoulder, dies readily available. It duplicates the ballistics of the vaunted 7mm Remington Mag, with 30% less propellant used and less barrel erosion.
  • .30-30 Ackley Improved, an improved .30-30 Winchester

.30-30 Ackley Improved (Left) .30-30 Winchester (Right)

  • .30-06 Ackley Improved, an improved .30-06 Springfield
  • .30 Ackley Magnum No. 1 and No. 2 short, based on the Holland & Holland belted magnum, the No. 2 version designed to fit in standard length actions (.30-06 class)
  • .303 Ackley Improved, an improved version of the .303 British Mark VII service cartridge
  • .338-06 Ackley Improved, an improved .338-06 A-Square (which is a .30-06 necked up to .338 caliber)
  • .35 Ackley Magnum No. 1 and No. 2 short, based on the .30 Ackley Magnum cases; there is also an Improved version of the No. 2.
  • .450 Ackley Magnum, based on .375 H&H Magnum necked up to .458
  • .475 Ackley Magnum, based on a .375 H&H Magnum necked up to .475 (12 mm)

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 5,000 ft/s (1,500 m/s) muzzle velocity. Ackley's loads only managed 4,600 ft/s (1,400 m/s), firing a 50-grain (3.2 g) 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, but in a cartridge case that routinely holds over 100-grains of powder, it is hardly worth the effort.[8]

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 4,798 ft/s (1,462 m/s) out of a 52-inch (1,300 mm) barreled gun.[5]

A .243 Winchester (right) beside the Ackley Improved version; note that only the shoulder angle is changed to the sharper shoulder angle typical of the Ackley Improved cartridges. In this instance the shoulder diameter of the Improved normally remains the same as the original case at .456"-.457" with no significant change in body taper. However, minor variations exist with some drawings showing a slightly larger .460" shoulder diameter.

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.


  2. Dave Moreton (May 1968). ".17-Caliber Ultra Bomb!" (– Scholar search). [dead link]
  3. P. O. Ackley. Handbook for Shooters & Reloaders. Plaza Publishing. ISBN 99929-4-881-7. 
  4. "Wildcat cartridges". 
  5. 5.0 5.1 Frank C. Barnes, ed. Stan Skinner (2003). Cartridges of the World, 10th Ed.. Krause Publications. ISBN 0-87349-605-1. 
  6. Dave Anderson (April 2003). "Pumping up the .223: experiments with a self-loading .223 Ackley Improved". Guns Magazine. Archived from the original on 2012-07-08. Retrieved 2008-06-10. 
  8. Ackley, P.O. (1927) [1962]. Handbook for Shooters & Reloaders. vol I (12th Printing ed.). Salt Lake City, Utah: Plaza Publishing. p. 442. ISBN 978-99929-4-881-1. 

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