I got my scope all mounted up today. I used a Burris ARpepr 1 piece extended scope mount 30mm to mount my Vortex Viper 6.5-20x44 30mm tube scope. Torqued everything down like the instructions said and then did my old fashion bore sighting. Look through the barrel at a spot on the wall across the room and adjust the scope to the spot. Discovered that I did not have enough adjustment so I had to unscrew the 12 screws that are on the rings and place some shims I made out of aluminum flashing material under the rear ring. I used three thicknesses. Replaced the scope and leveled everything once again and screw and torqued the ring screws back down. It then adjusted to my spot on the wall but not sure I shimmed enough. I will find out once I get to the range and see where I am shooting and how much adjustment I will have left.