I recently inherited a winchester model 12 in 20 gauge. Nice gun. I can immediately see it being employed to hunt pheasant and small game. I'm wondering if it's reasonable to hunt geese and ducks with a 20 gauge, and also if a 20 gauge slug will humanely take down a whitetail at 50 yards. I've got a 12 gauge that I've used for everything up to this point, but it sure would be nice to hunt at least the heavier birds with a gun that's a lot lighter, and less of a monster to shoot. Don't want to be wounding things though, if I can avoid it. Any advice?