Then I suspected the scope, thinking that it was bad, and in the process of removing it and replace it with another scope I had on hand, I discovered that the front scope ring was loose!
I went ahead and replaced the rings and mounts, going from Weaver style to Leupold standard mounts. I used the new mounts to re-install the old scope.
At the shooting range the next morning, despite a stiff, gusty breeze, I saw that my groups had shrunk dramatically.
Doh!
