Over the years/decades, I’ve shot hundreds of ducks and geese with factory 12ga 2 3/4” 1 1/8oz steel 2s and factory 20ga 2 3/4” 3/4oz steel 2s. I’ve never shot birds with a 16ga, but I would not hesitate to use factory 16ga 15/16oz steel 2s for ducks or geese. I think most of you guys are way over thinking this. It’s very easy to buy ammunition on line. One does not have to start reloading or spend months designing a bismuth load in order to shoot a 16ga. If you find a 16ga gun you like, buy it and shoot it.