try 6's all the time, i use 7/8ths oz 7's at 1100 in my 20 and 12 and it hit them hard out to 35 and 40 yds stone dead, remember these are shotguns not rifles. you can alway hit where you aim.i would just try smaller shot to fill in your patterns. i have shot geese out to 30 yds with 7/8ths oz bismuth 6's out of my tight choked 20( a 20 is not my goose hunting gun just in a pinch a few times
) and for them most part they are dead or not going any where. i load ALL my shell. i think the fastest FPS i shoot is 1250 1 1/4 bismuth out of a 2 frame 12 but for the most part i shoot between 1100 to 1190 fps and not to many hit birds go too far if any where at all
