I had forgotten my Michael Yardley "Gunfitting" book until early this morning. I pulled it out and read a bit on cast. He quotes Gough Thomas who says that POI moves opposite to the direction of the butt movement.
Regarding the distance tested and how much the barrel was off point of aim, it was shot many times at 20 yrds and was off approx 8-10" but I didn't have a proper measuring device.
Straight trig change would suggest that a change of over .300" change in barrel spread would be needed to correct this. Something is off big time. I'll check the barrels for a converging bend, then look at the chokes for proper alignment.
Again, the left barrel was spot on.
I've check my brother-in-law's mount and sight picture by having him repeatedly mount the gun and I peered directly from the muzzles down the rib to his eye. he has it mounted correctly with a correct sight picture.
