greyling
Pull the scope and look down the base to see if it is running true to the barrel , also is it a factory installed base ? if so you may need to pull the base , clean out the mounting holes and lap in the base then re-mount the base .
Take some fine grit sand paper , lay it on top of the frame , lay the base on the sand paper and work it back ans forth till the base has a true fit with the frame .
Once everything is re-mounted and the scope is back to center pick a spot on the wall about 25 to 50 feet , look down the bore of the barrel and see if the cross hairs are anywere close to the spot on the wall .
If all else fails they make a set of ajustable offset rings that may be needed .
hope this helps .
stimpy