.280 Ackley Improved
The .280 Ackley Improved (.280 AI) was the result of the .280 Remington case modification by P.O Ackley, who pushed out the sidewalls at the shoulder to near parallel and steepened the shoulder angle to 40 degrees in order to increase powder capacity, thus along with increasing the allowable pressure, resulted in increasing the bullet initial velocity by approximately 100 fps. == History == In 1957 Remington introduced the .280 Remington, which was based on the .30-06 Springfield case necked down to 7mm.