WE have shot literally hundreds of rabbits over the past 40 years (not a typo or load of bull sh@@t)... and most of them were shot with Sheridan .20 caliber C9 pneumatic air rifles or Benji HB20 pistols, netting 13 ft/lb and 6 ft/lb respectively... a .22 at 80-100 ft/lb is more than enough to cleanly kill bunnies... but most certainly aim for the head. A chest shot through the lungs is quickly lethal also... but it is often difficult to tell where the lungs are when they are sitting all balled up... the head is a sure target... aim at the "black smartie!" 
