First of all your friend has a great gun. Browning recommends a turkey choke with a .640 exit diameter llike their Full Strut Turkey Tube. I've shot that choke and it's a good one in many cases but I've done better with the SSX and it's about 1/2 the price of the Full Strut.
As far as shotshells, I can't find anything better and more consistent than the Hevi-13 shells. In that Invector plus barrel, I've found the 3" Hevi-13 "Bronze" shells with 2 oz. of #6 shot work best.
"If he's out of range, it just means that he has another day and so do you."