The .17 Ackley Improved is a wildcat cartridge, developed by modifying the .22 Hornet cartridge. Wildcat cartridges are non-standardized ammunition, often created by enthusiasts to achieve specific performance goals. The .17 Ackley Improved is known for its high velocity and flat trajectory, making it particularly suitable for varmint hunting and small game.
The modification involves necking down the .22 Hornet case to .17 caliber, fire-forming the case to have steeper shoulder angles, and sometimes increasing the powder capacity slightly. The result is a cartridge that can push a light .17 caliber bullet at extremely high speeds, often exceeding 3,000 feet per second (fps).
This high-velocity performance translates to excellent accuracy and minimal bullet drop at common varmint hunting ranges. One of the appeals of the .17 Ackley Improved is its low recoil, making it easy to shoot accurately. It is not widely available commercially and typically requires handloading, which means it's often used by more experienced shooters and hunters who are comfortable with reloading their own ammunition.
In summary, the .17 Ackley Improved is a specialized cartridge used primarily for hunting small game and varmint due to its high velocity, accuracy, and low recoil.