The lung area on a rabbit isnt that much bigger than the head shot.You might need to practice until you are good with the gun. At night, on the lamp, the rabbits always look alot further away than what they are. For most of the time you will be 20 yards or less, so try and get good groupings at that range.
Over the years i have killed alot of rabbits with body shots, but if they are near cover then forget it. Even when drilled through both lungs a rabbit can cover 30 yards. Also i have shot a wide variety of springers off rests, both vehicles, fence, wall and sticks and the accuracy seems goo