.22-250 Ackley Improved. It will give you a little more zip than the .220 Swift, without all the case life problems associated with loading that caliber up to its full potential.Never have to trim cases with the Improved.

If you don't reload, its a toss up between the .22-250 Remington and the 220 Swift.

PS - for a rifle, Remington 700 VS.