A little off topic here, but still a good story. During development of TSS, I was on a snow goose hunt with Kyle (the creator of TSS). A winged bird hit the water about 100 yards away. The guide asked Kyle if he thought he could swat that bird. Kyle quickly screwed in a turkey choke, took dead aim, and missed several feet short and to the side. The pattern of #5 TSS was still coherent (maybe 4' across), so he adjusted for windage & drop and fired again. This time the pattern just fringed the tail of the bird, making it swim a little faster. The third shot was the charm, covering up the bird. At first it didn't look like it was hit, but then it started to swoon and died fairly quickly. I pulled out my rangerfinder and lasered the shot at 131 yards!
Back on topic, it would be very difficult to swat a goose on the water with steel at 70 yards. Notice Lost's table. Even #4 steel only has 1/2" of penetration at that distance (can't imagine how much #7 steel would have
). I'm not sure how much penetration one needs to kill with a head shot, but I'm guessing it's somewhat more than #7 steel can provide. On the other hand, going for body hits is also problematic. First, the angle is very bad. Shooting at such an oblique angle means you need to penetrate a greater amount wing feathers, skin, fat, muscle, and in a lot of cases the back bone and/or ribs to get to the vitals (kinda like shooting through sloping armor on a tank - the slope increases the effective thickness of the armor). With a great deal of the body under water, you have a much smaller & tougher target to deal with.
Perhaps a slow, high-payload shell of #1 or possibly #2 fired through a turkey choke might have the pattern density necessary to ensure a head hit at that range, but I wouldn't count on it without some testing. It might be fun to mess with, but a bit of a headache to try to utilize in the field.