In the last two seasons in SoDak, I have used a variety of guns/gauges on wild phez.
In '05, I shot a 1905 12g Parker Full/Skt choked with 1 oz of #5's at 1150 fps. I was able to connect well at about 40 yds with the Full choke but there's just not much #5 shot count in a 1 ounce Skt pattern much past 25 yds. The #5 shot seemed to make up for the low initial velocity.
I also used a modern 20g with some fairly hot Rem Nitro Pheasant 1 oz, #5, at 1300 fps. I used this load in both '05 and '06 in SoDak on wild phez. I have nothing but praise for that load.
I shot several SoDak wild phez with a 12g modern gun using the "standard" 1 1/4 oz of #6 promo loads. They knock them down hard but sometimes the ones that get tailpipe shot will get up and run.