So i have come across this problem with two different scopes now. my new Nikko sterling arrived today. i mounted it and whent to zero it in. I ended up maxing the vertical turret out completely but my pellet was still dropping about 2 mill dots too low. (18 yards distance). this cannot be right at all. i think my gun may have a defect with the structure or barrel. last time, i solved it by putting a strip of thing cloth under the rear pillar and remounting the scope so it was slightly tilted downward. but over time it ended up sliding back little by little. Any idea why this is happening and any solutions. Thanks Good day