The problem with the scope base was actually what BobT described (it was the machinist "gunsmith" that fabricated the muzzle brake that pointed it out), and the play in the base caused the windage screw to loosen, which when fired damaged the rear ring. I didn't want to go into the detail of what happened to the first set up as I had to chuck it anyway with the ring and windage screw damaged.

Funny that rjtfroggy mentioned electrical tape. When I noticed my second set up scratching the scope I only had about two weeks before elk season, so I used electrical tape around the scope and re-tightend. It minimzed the scope movement, but didn't eliminate it (although I was fortunate enough for a dumb cow elk to give me a perfect broadside at 80 yards, so I couldn't miss even with scope issues). Both the rings and the scope tube are 1''. It's six months until next elk season so I've got some time to get a rock solid mount.

I'm just wanting some examples of tried and tested mounts that work on a 300WM, and then try them out. I'll definitely look into the Burris rings as two of you that replied use them.

Thanks for taking the time to respond!