Larger shot is a bit better, but not mandatory depending on range. I had success in the past with 20 ga 2-3/4" #3 buck but had no houses other than my own within a mile or three. BB shot would likely work just dandy. 3" shells? Phffft------

I am..........disturbed.

Concerning the difference between man and the jackass: some observers hold that there isn't any. But this wrongs the jackass. -Twain