I think gas port size depends on when the barrel was made. I literally just installed a DD 10.3" barrel dated 07/2014 about a week ago and i measured the port size to be .0785" (#47) drill bit. I have installed a Govnah gas block but havr not shot it yet, I am waiting for a SBR tax stamp.
I don't know about 086" but previous posts I have read have said that DD 10.3" barrels were .082"

