Buy a airgun rated rifle scope as it's actually two directional both the enertia from the spring and the air going oposite directions.Bushnell, Tasco,Leapers and a host of others make airgun optics.Get mts. that have a pin in the rings to prevent slippage and a recoil stop that fits behind the back ring to stop movement the other direction as well.RWS,Beeman ,B-Square and Accushot all make rings of such nature.I just picked up a RWS 350 Mag in .177 and have been doing some research.Harold