I would agree with JD. Shotgun penetrates much more than people expect. The best option in my opinion is a quality defensive pistol round. I have shotguns, AR's, etc. and my home defense gun is a pistol. It is more maneuverable than a long gun and using a good, fragmenting defensive round will reduce the negative effects of penetration (to a point). The key factor is shot placement. You are legally responsible for every round you fire. Good center mass hits with a good defensive round is the best answer to avoiding over penetration of drywall in my opinion. Something that dumps enough of its kinetic energy efficiently into the target will do a lot less to drywall and beyond....if it even exits the threat.