I have the Franchi Affinity with the 26' barrel.  With Fed HW 7s, I settled on the Carlsons' choke.  This gave me a more consistant pattern than than the Hevi choke and Hevi 7s.  Try the Carlsons' and I think you'll be pleased.  I don't remember how many pellets I had at 30 and 40, but that's what I'm using.