I like 7 1/2s, too. In my 20, with IC, he gets into about 25 yards, I own him. Modified gets me out to 35 or so. If he's farther than that, he's safe. I tried IC/full last year, but full is just too much choke, gotta be WAY out there and you really have to be on him. With my 12 gauge auto, I choke modified.
As for ammo, I picked up some 100 round federal bulk pack at wallyworld the other day. It patterns decent. I've got five boxes of Winchester AA left for the 20, but it's sorta getting expensive. It sure patterns well, though. I have some boxes of Winchester super speed to shoot up in 12 gauge. It's all 7 1/2. The 12 gauge is 1 ounce loads and the 20 gauge stuff is all 7/8 ounce.
I've run a couple BOXES through mine since May. LOL Have to do. That was at a club country doubles shoot I didn't win. Oh, well...LOL Year before last I shot 3.5 boxes of 12s for 3 limits and last year I shot about 4 boxes for 3 limits with the 20. I think switching the back trigger from full to mod will help. I missed some birds with that full choke, did much better on the IC choke. I ain't the world's greatest wing shot, but I do have fun. As Dave alludes to, I probably don't practice enough at the range. I tend to get better as the year goes on. I do a little better on ducks. Ain't so much the size as the fact that doves are wily little farts that don't seem to like getting shot at and dodge and dart and seem to have better aerobatic skills. One afternoon I went 9 for 11, best I've ever done. To this day I don't know how I did it. Luck, I guess. LOL