John, I just saw this and will try to shed some light. I have been a 835 .670 pure gold choke, 3 1/2" Hevi 7's guy since 2009 (300 plus). These guns Love Hevi 6's and 7's and LB 6's with a choke around .675. Clark Bush did extensive research with this ammo and .670 Pure Gold, .675 IC, .670 SSX and .676 Stardot/Colonial chokes when Hevi and LB's first came out. Most LB 6's were putting up numbers around 250 to 280 then. .683 is slightly more open choke so.. Type in Clark Bush or Allaboutshooting and you should come up with TONS of info from his early shooting experiments with LB's and chokes. Great guy with tons of information on this subject but he has since passed away. Hope this helps.