My guess is that Knapp is using 1-oz. loads, or maybe even lighter. Most of his trick shots are close-range.
Even the kick from the 1-1/8 oz. load can add up quickly, especially in a lighter gun. I went to Argentina once with Federal ammo to "field test" some new loads on ducks and doves. Included were a few cases of 12-gauge trap loads. After the first morning NONE of us wanted to shoot any more of those in the relatively light bird guns we were using. Of course we wee shooting 100+ rounds an hour, which makes a difference too.
