Very odd thing, I have never seen this before, I'm upgrading a scope and mounts on one of my Remington rifles, ordered new Leupold Dual Dovetail bases and Burris Dual Dovetail Signature Rings, the rings just spin freely in the bases, no friction fit at all, so I get a used leupold ring that I had in my junk box and that spins freely also, so I conclude that it must be the bases that are machined out of spec, I send them back to leupold for replacement, today the new set arrives and I have the same situation, could it be another set of bad bases?

Has anyone ever seen this before?

I have the same problem with a pair of 30mm rings the front ring just spins. They work with none of my leupold bases yet every other ring I try fits fine.

Are your rings Burris brand?

no they are Leupold rings...