I've killed at least a half dozen deer with my 20ga, and that is a smoothbore with no scope. If you sight it in just like you do all your other guns, you won't have any problem taking a deer down. I only use my 12ga now because the 20 is just too "pretty" to beat up, and because I have a rifled barrel for the 12. If I had to choose only one shotgun to deer hunt with, it would be a 20ga with a rifled barrel.

--Man who fish in other man's well often catch crabs--