Wild pheasants are very different than preserve birds. Last December, I killed 27 preserve birds straight with a 28 choked IC/M and either 3/4 oz 7's (reloads) or 7/8 oz 7 1/2's (Fiocchi Golden Pheasants). This was over experienced pointing dogs, either mine or the preserve's.
I would never hunt wild roosters with a 28 unless I were prepared to pass up a lot of legitimate chances--not even with my own dogs, all 3 of which have seen a lot of pheasants. But you don't need to overdo it either. If you're hunting over good dogs in good pheasant country, you don't need really heavy loads. I shot over 60 wild roosters this year with a couple of 2 1/2" Army & Navy 12 bores. Right barrel choked 005 on both; left choked either 015 or 025. I switched to the #2 gun with tighter L barrel late in the season, but on reviewing my notes, I probably didn't need to. Never changed my loads throughout the season. 1 1/16 oz Brit 6's (slightly larger than American 7's) in the R barrel. Factory stuff, either Eley Grand Prix or Kent Pure Gold. L barrel, my own reloads of 1 1/8 oz American 6's at 1200 fps. Shot as well last season as I ever have on pheasants. But I am hunting good pheasant country with experienced pointing dogs. Not very many shots longer than 30 yards.