I clean the scope and rings with brake cleaner and then use clear glue that's found in Walmart's craft section, Duco Cement comes to mind. The very last stuff bought is Loctite Vinyl, Fabric & Plastic Flexible Adhesive at K-Mart. Both kinds are removed easily with brake cleaner or acetone. I don't shoot rifle, this is for hard kicking handguns...44 magnum and on up to BFR .475 L and .50 Alaskan Encore. Never, and I mean never had a scope slip using this method. After it sets, I push the excess that squeezes out with a wood tooth pick.