Using anything less than .23 cal on deer in KS is illegal but David Petzal did an article on the subject earlier this year. From what I remember, he said that small-bore rifles can work on deer, given that you're not using varmint or FMJ loads and the shot is 200 yards or less. If I could, I'd like to try a .220 swift on a deer in my lifetime. At 200 yards they're still packing over 1000 pounds of energy, and the hydrostatic shock is supposed to be brutal.