I put a shaw bbl and new stock on the 10-22, ordered a cheap scope from CDNN, 10-40x50. Put it on and is great, but ran out of adjustment moving the impact up. Best it will do is shooting 4" low at 50 yards. The scope is currently sitting real close to the bbl up front, so I cant simply shim up the rear ring. shimming the base would cause priblems of the base screws to short then. Is there an adjustable base or rings for the 10-22? Wallacem