Unbelievable
If your interested
1) Single piece mounts like LaRue and ADM where there is a vertical protrusion from the base that contacts the scope tube from underneath. The two ring halves clamp onto that protrusion on the bottom and are then tensioned on the top
2) Symmetrically split separate ring halves like those on Warne rings. These come in two varieties: permanent attach and QD. With permanent attach, the two screws that tighten the rings onto the rail can potentially be loosened/opened when the top screws are tightened (that is what the Youtube video someone linked above showed). With QD set-up there is a separate clamp that grabs the rail, so with those, tightening the top screws is not going to effect how well the ring grabs the rail.
3) Asymmetrically split two piece rings like Vortex Viper. With these, one side of the ring and the bottom form a single unit. The ring clamp is separate and is not affected by any of the screws that are used to secure the scope. With these, you tighten the bottom two scews all the way and then secure the top two screws
4) Vertically hinged symmetrically split one piece mount made by Aero Precision. WIth this one, the ring halves hinge together at the top and you tighten these at the bottom, so you have two screws per ring.
Obviously, all of these can be susceptible to out of round ring halves which can apply assymetric pressure to the scope. I can definitely attest to that happening with the Type 4. I bought several of these on sale a while back since I was intrigued by their light weight. Half were out of round, so I had to lap them lightly. Once set up, they seem to stay put and the scope stayed zeroed. They do no return to zero well if removed, but they are light cheap and stay put after installation.
I have seen out of round Type 2 rings as well (I have a lot of mileage with Warne rings), but my take on these is largely the same: I try to not use them for tracking tests, but once set-up they stay zeroed. I have seen a couple of "out of round" 1" and 30mm models.
With Type 1, you can have a sort of a unique problem where the scope slides a little with respect to he base, since the bottom of the rings clamps onto the base of the mount, rather than onto the scope. These were all "set and forget" types.
With Type 3 (Vortex Viper), it sounds like they should work fine if they are not out of round, but no experience here
