Ol' timer, I shoot one of the old star dot .676 choke tubes out off my 835 with longbeard 3.5", 2oz. Loads of #5 shot. My 20 yard pattern is more like a volleyball size at 20 yards and if memory serves me right it's around 190ish in a 10" circle at 40. For some reason my pattern isn't as tight as most and I am good with it. Still plenty good at 40 and a little wiggle room.
My observations so far are leading me to believe a tighter choke fractures the resin more and opens the pattern slightly.