My Krieghoff Teck .458 WM O/U double rifle has interchangeable barrels in 20 gauge 3" Magnum, and it did well on ducks as well as sand grouse. Nothing like hunting ducks from a bright yellow native canoe and propelled by six stalwart paddlers!

What I shot was Hottentot teal and some coots for the local populace. The teal were exceptionally good eating.