The .17 Ackley Bee is a wildcat

Wildcat cartridge

A wildcat cartridge, or wildcat, is a custom cartridge for which ammunition and firearms are not mass produced. These cartridges are often created in order to optimize a certain performance characteristic of an existing commercial cartridge.Developing and using wildcat cartridges does not...

 centerfire rifle

Rifle

A rifle is a firearm designed to be fired from the shoulder, with a barrel that has a helical groove or pattern of grooves cut into the barrel walls. The raised areas of the rifling are called "lands," which make contact with the projectile , imparting spin around an axis corresponding to the...

 cartridge

Cartridge (firearms)

A cartridge, also called a round, packages the bullet, gunpowder and primer into a single metallic case precisely made to fit the firing chamber of a firearm. The primer is a small charge of impact-sensitive chemical that may be located at the center of the case head or at its rim . Electrically...

 named after its designer, P.O. Ackley, and is a .218 Bee

.218 Bee

The .218 Bee is a .22 caliber centerfire rifle cartridge designed for varmint hunting by Winchester in 1938. The cartridge was originally chambered in lever-action rifles, which may have ultimately led to its lack of popularity...

 case necked down to .17 caliber with a squarer shoulder and less body taper. Being a rimmed case it was popular with single shot rifles such as the Martini Cadet

Martini Cadet

The Martini Cadet is a centrefire single shot rifle produced in the United Kingdom by BSA and W.W. Greener for the use of Australian military Cadets. Based on a miniature version of the Martini-Henry it was internally different...

 and Low Wall Winchester. The caliber is well suited to varmint hunting particularly where minimal pelt damage is required.