Well, I'm back. I checked my barrel, which appeared clean and defect free. There was one screw on the scope base which needed a little snugging-up.

I switched from pellets to powder (Shockey FFg) and got two different types of bullets (TC Shockwave 250gr, and Powerbelt Aerotip 245gr). I wound up using a 90gr load, and the TC's gave me good results. When I shot the powerbelts, they hit about 8" to the right. I couldn't believe that a different bullet would be so far off. In any event, I seem to have resolved my issue.

Ed