The federal heavyweight have the flight control wad which does not perform well in ported chokes like the SSX .643, every good pattern i have seen with the heavyweight # 7(although not many) is a non ported choke . I have the same setup(870/ ssx) and shoot magblends with good results. If it is the 10 inch circle you are concerned with try some longbeard #5, they were devastating at 40yds but were just too tight at 30 and below for me. Heavyweights pack a heck of a punch though so in my mind you dont have to have quite as many in his head and neck to the trick.