hmmm i think a 3 1/2 inch is your best bet but you can do with a 3 inch if you keep shots closer...i use a modified choke with a 3 inch mag in my mossberg 500...though i never got to shoot a duck or goose out of hte air im sure i could take one...i now have a mossberg 500 with a 28 inch barrel(good for just about everything under the sun) and a 870 3 inch mag for turkeys and just turkeys with a 21 inch barrel..but the 870s and 500s are nice guns...the 835s are pretty heavy and if you walk far you will begin to hate...stay with a barrel around 28 inch or so for wind shooting....
