My mate went out with two brothers (both in their late sixties) shooting pigeons, they always said it was the cartridges that killed the bird/animal not the size of the gun. I have shot 12g, 20g and 410s since I was 14, it is personal preference most of the time that counts, what you are comfortable with and how good you are with the gauge size. I cant shoot any gun bigger than a 410 for a few months had to sell my 20g because the kick would damage my shoulder after having surgery , not everybody that has a 20g is a whimp. Its not how big the gun is, its the way you shoot it