It is very common for people to leave ring screws too loose because they are afraid of damaging the scope.I use the leupold rings and bases myself and tighten then as tight as the little wrench will allow without bending.Even with heavy recoiling rifles I have never had a scope move or screws loosen.As to your grouping it may just be that your rifle does not like that particular load.If it doesn' t improve when the scope is properly tightened you may want to try another load.