JD has the right idea. WHen I work birds in preserves, 2 3/4" w/6 works just fine. I' ve even started the habit of using my 28g. on these liberated birds. High plains wild roosters are a different bird altogether, though. Not only are they bigger and tougher physically, but conditions usually require a heavier load. The winds of my homestate are notorious for eating shot patterns. We normally go with max dram 2 3/4" shells with 5' s or 6' s, Mod/Full (O/U).

The guys using flushing dogs go so far as to use 3" #4' s for late season birds.