Snarer,
Did you get the Carlson extended turkey choke? If so we should compare results. One of the rigs I am due to pattern soon is a 1952 870 3in chamber 30"barrel 12ga with the Carlson extended turkey tube .665. I will be testing Hevi-13 6s as #7s are not legal here in Oregon for turkeys.
If your set-up is the same/similar it might be interesting to post both our results (measured 40 yards at a 10" circle) and see what we get.
Dan