A twenty gauge is fine unless you want to push the range. That being said, my son killed a bird with a 20ga. using 3 in. #5 HeviShot at 55 yds this year. Last year, another son killed one stone dead at 30 yds with a twenty gauge, 28 in. full choke barrel, and 2 3/4 in. #6s. We killed a bunch of birds the last couple years with 20 gauges, but I'd stick with a 12 if I had to choose.

Hal