With just the information given: First WOW on the velocity! Its a wonder the scope remains in place not to mention your shoulder.
When I had those kinds of problems the solution was degrease, degrease, degrease. Then tighten ring screws (on the scope - burris sig. bases) until the wrench that came with looked like it was threaded instead of straight. I hawg'd the squat out of things.
Can't be sure because his description isn't really very clear but it's entirely possible he means that the round outer housing, with the single screw in the center, is coming loose and rotating. If this is the case he needs to do a search as this came up before and led to a lengthy thread if I remember right.
I don't think "W" transfered over to the new site as I don't see him in the member list, but he can be contacted at his web page if there is a problem with the product. Sniper Tools Design Company - angle cosine indicator