TOTAL BULLSHIT, NO RING, GOES BACK AFTER FIRERING, they all stay forward, and or move forward if not pushed there. All military mounts are made to fit the mil spec slots in the receiver, for the very reason that the cross bar will not get hung up from going onto the reciver from mud, etc.hence nothch clearance by mil spec! The answer you got from ARMS and or will get from any other mil spec maker will be the same, whether you understand it or not is another issue. There are a lot of undersize out of spec receivers out there that a throw lever won't be tight on, but the scope still doesn't go back from recoil, since for every action there is a reaction, Physics ONE, experience two. Undersize receivers also make the ring tilt more than it should to the left if the lever or knob are on the left, tilt to the right if tightened on the right.
Jack