Something else to consider is that semi's don't have less recoil that anything else but the recoil impulse is spread over a longer period of time as the action cycles giving the illusion of less felt recoil.
In my experience, the lightest recoiling shotguns are over and under's that are designed for heavy use and are heavier than hunting guns with good fitting stocks, long forcing cones, over bore barrels and long choke tubes. such as 692's, 725's, Dt-11's, Perazzi's, K80's and Zoli's, etc.