My rings on a 30:06 had the screws down tight, so I shimmed the with black eletrical tape. When sighting it in I noticed ths scope slip back towards the rear of the gun.
I was up in the woods so I used the cardboard off a box of 22 RF. I had a screw driver and took the rings apart and carefully cut the pieces and shimmed the rings. Tightened the screws med. tight. There was still threads left. Shot it twice and it holds fine.
I used the thicker material on the rear rings, and have more elevation adjustment on the scope. It's a old Weaver 4x. Gun stays sighted so far and shots great.