I own 12 & 16 gauge Ithaca's Love them, But own a Winchester 1300 with screw in chokes & plan on getting threw Cabelas a Screw in Slug choke, so i can use it this deer season in NY , You can kill a deer with a rock if you hit it in the right spot, 20 gauge's will kill just the same.

P.S Never met anyone (yet ) that has killed a deer with a rock.