Are the two rings the same? If yes, you might try switching them. Also, since you have your elevation cranked all the way up (which means the horizontal cross hair is all the way down), you might crank it the other way, counting the turns. Once you do this, crank it back half way so that it is centered. Start your bore sighting from this point.
I had a BAR with a similar problem, shooting low and no more scope adjustment. I took the scope off and then put 2 layers of black electric tape on the bottom half of the rear ring. Essentially shimming it. Raising the rear of the scope causes the cross hairs to move lower, towards the current low POI. Doing this will help raise the POI. Will it be enough, try it and find out.