I had the same type of Warne rings on my MKII FV and it wouldn't group for squat. I thought they were tight, but there is still a bit of play in there sometimes. I just decided to use a different brand of ring. I love that EGW base . I would try different rings before you went and tried a new scope, cheaper too.

Here is what it used to look like with the Warne rings and EGW base

[img width=600 height=450]http://i715.photobucket.com/albums/ww156/killswitch12_2009/CIMG0415.jpg[/img]