I'm kinda surprised the full choke gives the better pattern, as I figured a loose modified would be better for trying to jam those marbles down the pipe? But what do I know?!?!?

Todd, when you mentioned your shells..have you cut open one of the shells and noticed the 00 deformed before firing? Is there an actual wad cup surrounding the shot, or just an over-the-powder wad?

I'd wager Knick's pellets have some/more % antimony in them (premium shell), which makes them "harder", but a tad bit lighter. Copper coating is supposed to be slicker in transit down the pipe, less deformation through the choke as well. I'm a believer in buffered loads, especially if they're HOT as the buffer mitigates deformation on ignition.

Copper-I always thought was a sales pitch. As long as I had a high antimony content shot (like 5%+) that made the shot "hard", way harder than "chilled" lead shot. Easily distinguished by the "crush-test" with needle-nose pliers. When shooting trap at night, if one really paid attention, you could tell who was shooting copper shot (and on the rare occasion, who was shooting nickel plated shot) by the reflection. Kinda cool useless info..