#4 or #5 shot work just fine. But umm I am going to go against the grain here, I love to eat squirrel stew and have used many tools to take them, I don't like shot in all of my meat, nor do I like to bust them up with the .22. I use my Crossman Powermaster ( a very accurate bb gun too I might add) with 4 power scope to take them, yep thats right a BB gun. And I have found that it doesn't scare the rest off for a while like using the shotgun or 22. just my .02