it’s likely not your scope: Barrel Droop
Barrel Droop Can Make Your Head Hurt If You Don’t Know What’s Going On
When a gun won’t sight in, it is seldom a defective air gun scope. Also called barrel angle, “Barrel Droop” – a slight angle between the barrel and receiver is a common condition on air guns – even fixed barrel guns. With the iron sights mounted on the barrel they automatically align with the bore and any droop is not likely lead to an accuracy problem.
Air gun scopes, however, are mounted on the receiver which means that the scope (or the mount) must be able to correct for any droop in addition to normal sighting function. Just one degree of droop will throw you off about 7½” at just 10 yards or about 300 clicks! Most scopes can’t handle much more than that (if that much).
The least expensive way to correct for barrel droop is the simple shim. A shim, made of any suitable material, may be placed between the lower part of the scope ring and the airgun scope to raise the forward or rear end of the scope. Another way to overcome or avoid this condition is to use an adjustable air gun scope mount (like the RWS “C” Mount or the Beeman 5039 Adjustable Mount). An adjustable air gun scope mount has the ability to raise one end of the scope to bring it in line with the barrel. This may not be necessary with all air guns, but must be kept in mind. Unless you know that the barrel angle is correct, adjustable mounts are often cheap insurance against potential barrel droop headaches.
Most frequently the airgun will shoot low. To raise the point of impact using an adjustable mount raise the rear end of the scope. Do the oppsite if you need to lower the point of impact. Many adjustable mounts will also correct for horizontal alignment in a similar fashion. Follow the directions that come with the mount.