You've just got to try a bunch of different kinds to see which patterns the best. In my 20 gauge I use an extra full Hunters Specialties Undertaker choke with Federal premium mag-shok #5 turkey load with a "Flitecontrol" wad, and of course its a 3". Last year I took a 24LB turkey with a an 11" beard with inch and a half spurs. Only $10 a box to. One of my friends paid $50 for a box of 3.5" 12 gauge turkey loads only to do the same thing I can do.
i use hevi shot in both the 20 and the 12. 3.5 in the 12 didn't work as well as the 3. the 20 with the true glow turkey choke and 3" 4 or 5 is killer. i tried the new stuff from federal magna shok, i think it was, its the heavier than lead, it didn't do as good as hevi shot in my guns.