Check out the 2nd sticky at the top of this forum page, it is there for a reason. I had a problem with the factory rings on my 6.5x55. The problem is that the front ring has a recoil pin, but the rear one doesn't, and there are two screws per cap. With all screws tight, the rear ring eventually slid forward on the dovetail and the scope slipped forward in the front ring. Switched over to the Talley lightweights on that rifle and my 338WM and haven't had a problem since. Relatively low cost (no separate bases to buy), light, 4 screws per cap and very well made. I'm sold on them.