I have 2 CZ 457's, one American and the other is the Varmint model. They both have Burris rimfire signature rings mounted on the 11mm dovetail receiver cuts. The bases on both walked forward on the dovetail after 40 or 50 rounds of SV Geco ammo. I retorqued the base to rails to 30 in lbs and had the same issue! The small instruction manual that comes with the ring sets call for 60 in.lbs for the base to dovetail ring and 35 to 40 for the top ring. This sounds excessive to me. I am now going to try 40 in.lbs for the bases and see what happens. Any input appreciated. Thanks, Mike.