The scope on the precision "Sierra" rifle is mounted sideways in all the scenes that Ed is holding it. In reality the turrets are always on top and on the right. The turrets show in several scenes on the top and left side. The the dial for the cross hair lighting is always on top or 45* angle to the right of the eye piece, not 90* to the left hand side as shown. This would indicate that the scope is actually mounted sideways, and the shot hasn't been mirrored.
When Terry Dornan jumps from the roller coaster, he does so by leaning forward and is initially shown falling front first. However, when the camera cuts back he is shown falling with his back to the ground, with no indication as to how he changed orientation.