DairyFarmer is right..the .17 HMR may be smaller but you'll hit WAY harder than a .22 LR because of the increase in muzzle velocity and the kinetic energy is proportional to the velocity squared.
See
http://en.wikipedia.org/wiki/.17_HMR#Comparison_with_.22_LR_Ammunition esp. "overly destructive to small game at close range" lol [/quote]
see I knew it was math stuff