I picked up a couple of boxes of the #2 federal 3" 20ga buckshot. Its as good a 20 ga hd round as any I've seen. Pretty brutal at close range... And slightly more forgiving at adrenaline influenced aiming than a slug. It was kind of pricey... $8/5 at a local gunshop. I could probably find it cheaper elsewhere if I looked. I can afford to practice a lot more with my 12ga.
If we're out shooting clays at the property and we get any aggressive coyotes or coy dogs visiting... I'll be glad to have a few rounds of this around.