I've hunted wild pheasants in Iowa since 1975. I started with a .410 3 inch full choke shooting 6 shot (thanks, Dad!), then went to 12 gauge 2 3/4 inch. I hunted a lot one year with a guy who fancied 3 inch shells, but he paid more and dropped the same or fewer number of birds as I did shooting 2 3/4 inch shells. At first, the 12's were full choke, but then I went to modified. I would not use any shot smaller than 6's. I've shot most of my birds with low base 6 shot rather than magnum loads. Late in the season, when the birds get jumpy, I might go to 4's. 5's are my favorite. If hunting over pointing dogs (or close working flushing dogs), IC to mod with 5 or 6 shot should suffice. If you want to shoot birds that are flushing wild, full and 4's would be the way I would go. I've never hunted a preserve, so can't offer any advice about that. Good luck and hope you have fun!