If you spend some time on the old gobbler forum, you will start to see the best pattern numbers are coming from the Mossy 835.
The 835 has a bunch of things going for it,its not too expensive, you can usually find used ones real cheap, it will eat any size shells, and its overbored which is giving it its great patterns.
You can get a whole setup, choke, some kind of optic if you want, etc... for less than some people spend for bare shotguns, and the 835 more than likely will beat it out pattern wise with the right choke and load.
By the way, this is just what I see from numerous pattern pictures and other hunter's testimonies... I don't personally have an 835, but if I were to start from scratch for a turkey/predator combo it would be an 835.