Wasn't aware that Mossberg is making bows.......

Anyway, I shoot a 500 with accuchokes, I use the standard full choke with 3" Win. Super X #5 turkey loads. Dead turkey out to 30 yds, no problem. I generally set up where if I can see the bird, he's within 30 yds.

A "better" choke may gain you some range. Be sure to pattern it, and limit your range to the distance that you consistently get a dozen or so pellets in the head/neck.