I know lots of folks don't like them, but the least problems I've ever had with bases and rings have been Weavers. They are aluminum bases and steel rings. They don't look that great, but they have never moved on the guns I've had them on. That would include a 300 Wby and a 338 Win Mag. The Weatherby was an Ultralight that weighed 8lbs with scope. When I was shooting 200 grain factory Weatherby ammo, and Federal High Energy loads, it defined the word "recoil". Scope never moved.