Remington Nitro Mag shows the 2 3/4" 20 ga Buffered Magnum in #4 bird shot. We use these in #6 for pheasants in our light Franchi 24" quail autos. Makes longer shots on pheasants with the short IC barrels. If you use some kind of a double barrel, a slug in one barrel and birdshot in the other might work. When in my youth, we had coyote drives each Sunday with lots of hunters. We always killed a bunch of coyotes and buckshot was prohibited.
Remington only lists #3 Buck for a 20ga.
