I also use #6.But remember, certain shotguns pattern different shot sizes better than others.My Ithaca patterns #6 shot better than #7.5 or #8, so I always use #6 on birds as well as squirrels.
Your gun might pattern #7.5 or #5 better than #6.And it might pattern a certain brand of shell better than others.
BTW, I still use an old fashioned polychoke.
