I try to avoid 6's for pheasants, as they leave too many pellets in the meat, but I certainly would not use them on late season jumped birds.
At 30 yards there is no choke that produces as good a pattern as a full choke. The more open you go from that, the more you are handicapping yourself. (Bob Brister wrote a book about that back in the '70s.) Mod is a good compromise in case you get some 20-yard shots, but I would prefer to avoid IC for 30-yard-plus shots. You still have a hot center, but it is small compared to that of an IM or Full.
I haven't had anything tighter than an IC in my 303 Beretta in over 2 decades. ICs in my 20ga Beretta 626 SxS. Cyl in my Beretta 303 20ga.
My longest kill last weekend was a hair under 60yds and stone-dead, so maybe I oughta tighten up my chokes.
Of course, I shoot turkeys w/IC and 2 3/4" 1 3/8oz 4's or 5's too...........
