I had a Parker Ballard 30.06 that my father purchased for me with those type mounts made by weaver. It held zero but I eventually replaced them with a normal set of rings mainly because I kept worrying that it suddenly wouldn't hold zero lol . This took place in PA in the 90's.We had them on a lot of deer rifles in PA back in the day (1960 - 1970s). Mainly for rain or snow issues . I still have couple laying around. The Weaver ones held zero pretty good.