I gave this question to Philip Bourjaily, who answers: "I recommend the 20-gauge Youth Model Remington 1100, which has very soft recoil. As for shells, 23/4-inch 3/4-ounce loads of No. 4 or No. 6 steel will kill ducks at moderate ranges with fairly low recoil. Federal, Winchester, and Remington all load such ammo."