If the "area low is where the back screws mount, causing the scope to tilt UP in front", then certainly the gun would shoot low. I agree completely.

That situation is entirely different that what most would call barrel taper.But, call it whatever you want, a "low area" in the vicinity of the mounting holes seems like a bad thing, and likely notan element of the design. If it does exist as a knownfrequent issue, that would seem to be a QCproblem.