Salopian, I would never claim to be the best wingshot in the world, and I probably would indeed benefit from a shooting lesson. My point, however, is how much better of a late-season pheasant wingshot I suddenly became when I switched to #4s. Now when I shoot, the bird usually falls dead, rather than an apparant miss or a crippled bird. Coincidentally, the same instant improvement has been experienced by several of my friends who have also switched to mag #4s for late-season wild birds.
As for your advice on not lengthening the chambers on my beloved Superposed, I don't know if I could bring myself to do it anyway. Just an idea I was toying with and wondering about feasibility and approx cost.
A5guy, here is some data you might be interested in: Your 1 ounce #6 loads actually have 21% more BBs than the 3" mag 1-3/8 ounce #4 loads I shoot late-season (225 vs. 186) and 33% more than the 2-3/4 oz #4 loads I shoot at pen-raised birds (225 vs. 169). IMHO, the only advantage of smaller shot is pattern density. However, on a bird the size of a pheasant pattern density is really not an issue until you get out to longer ranges where #6s and #5s don't have enough energy to get the job done anyway. To wit, at 40 yards #4s have 26% more energy than #5s and 91% more energy than #6s(!), assuming all had same initial velocity of 1330 fps. We could debate chokes, starting velocities, etc., but the point is that #4s have LOTS more energy at long ranges. Although the loads I shoot have fewer BBs than your 20-gauge loads, they provide adequate pattern densities and far superior knock-down power at the longer ranges I experience with late-season birds. For the type of hunting I do, it makes a very noticeable difference.
Grizer, you're asking the right question. On late-season wild birds I shoot Mod/I-Mod at average ranges of 35-45 yards. I take some longer shots, but even 3" mag performance beyond about 45 yards is marginal. On pen raised birds, I usually only shoot after my guests have missed. So, those are also longer shots (maybe 40-45 yards average) and I shoot Mod/I-Mod then also. I have tried Full in the top tube for both types of hunting, but it doesn't seem to give me any more effective range than I-Mod.
And contrary to one of the posts, I can state positively that it is much tougher to bring down a bird when it's flying straight away from you and the kill zone is not much bigger than a silver dollar than it is when they are crossing or flying at you and the head, neck and breast are exposed.