I have a .670 tempest choke and I tested it with the Federal FCW 2" #5 shells. . . .it gave good results but the .643 SSX choke was substantially better with those loads. I had a small stash of the old Federal 2" #5 shells and the Tempest shot those REALLY well. That was the combination I used this turkey season with great results. Overall I'm happy with the tempest choke but patterning with my BPS (26" barrel) suggests that it may not be the best choke for the FCW shells. That's not to put the tempest choke down, I really do like it.
Hope this helps!