I've been tearing my hair out trying to get the scope on my springer properly zeroed. I tried different mounts, making sure my eye position was correct to rule our parallax error but still I have a problem, which is as follows. I zero my setup at 30 yards, however I fine tune it for lateral accuracy at 40 yards because one of the markings on the reticle falls at 40 yards. If I then check my aim points I find that closr than about 30 yards the pellets start to impact to the right of my aim point, and at 10 yards they'll be as much as 1/2" out, or even more. But at 45 yards they'll be slightly to the left of the aim point. Crossover, you'll say. Change the mounts. Which I have done. Several times. To no effect. I started to wonder if I'd maybe knocked the rifle and bent the barrel. So I finally changed the scope and now find pellets are lending pretty much where they should be. So my question is: can a scope have a lens / reticle or tube fault that might cause such a problem?