While having a M4 with an ACOG sight equipped. Whilst in a fairly sizes city on a rooftop. Lay down in the prone position. From here aim down your sights (left trigger) then look through the scope (right bumper). Continue looking through the scope and begin to turn around while aiming through the scope. Left or right, it will not matter. Once you get to a certain point, roughly 3/4 around a full circle the scope will begin to rotate back to normal. When this starts to happen a severe frame rate loss and detail to map is experienced.