I upgraded and put a steel breech on my Crosman 2240 so I could use a red dot sight. I have a couple of Vortex Venom sights tried both using some of the UGG Weaver to 11mm dovetail adapters. With both my POI at about 8 yards is 5" low, with the red dot adjtusted to maximum up. Could I have barrel droop and if so what can be done.