Based on my reading, I think #4 buckshot offers a good mix between stopping power and risk of overpenetration in the scenarios that I would be using it. A bit of a moot point right now, insofar as the local Cabela's had absolutely no 12 gauge # 4 buckshot on the shelves. Cases and cases of birdshot, several boxes of Herters defense load (O buck plus one large ball) and a few boxes of Olin 00 military buckshot. Similar slim pickings on the 20 gauge and .410 shelves as well.