Ackley Improved version of the .243 Winchester; improved case geometry adds velocity for varmint and deer hunting with a proven cartridge.
Type: Rifle
Introduced: 1955, United States
Parent case: .243 Winchester
Standardization: Proprietary
Bullet diameter: 0.243" (6.17 mm)
Rim type: Rimless
Primer: Boxer Large Rifle
Production status: Active
Also known as: .243 AI · .243 Winchester AI
History: The .243 AI improves the already versatile .243 Winchester with a sharper 40° shoulder and more upright case walls, adding 50–100 fps depending on bullet weight. It is a popular choice for hunters and varmint shooters who are already set up for .243 and want to squeeze more performance from the case.