id deffinalty go with 3 inch, i shoot a benelli nova and use 3 to 3 1/2 inch shells shooting bb to bbb. 50 yards seems to be a bit long. the shot likes to bounce off there feathers. the closer the better. i use to use a remington 870 that only accepted 2 3/4 inch rounds and that did just fine. but the 3 and 3 1/2 got alittle more range and bring down power. hope that helps.