Miller, I don't know whether Brister knew what the "other factors" were either, but what he knew from shooting lots of targets and patterns (and birds) was that the 28 simply performed better than he would have expected. There's something about the combination of that shell in that bore that just seems to work particularly well. I've shot straights at skeet with the blasted thing, and I'm not Brister. And I've watched way better shots than I am shoot skeet with a .410, and I'm convinced it'd be pure luck if I ever shot a straight with one of those.
You're interpreting what Brister says as: the 3/4 oz 28ga load and the 1 1/4 oz 12ga load are mathematical twins. Don't think that's what he's saying. I read that as Brister saying that those two loads are examples of particularly "well-balanced" loads--based on performance, not mathematics. There's something about both of them that makes them work particularly well in their respective bores. That something, obviously, cannot be defined by mathematics. I think you would have left much out of his book, had you written it, and entitled it simply "Shotgunning: The Science". He's saying it's not all science; some things happen that you don't expect based on mathematics, the performance of the 28ga being one of them. And as both a skilled hand with the shotgun and an experimenter, I think he has sufficient credentials to say that there's some art in the whole business. Hence, the title of his book.
