Badger, been my go-to for a long time now. No frills, no bullshit, just solid rings and mounts. In addition to regular width, they also make wide spaced mounts that will accept a large USO erector so that's nice. Different heights, MOA, etc., full line of mounts and rings for mounting clip on NV.
I use their SASR rings for the .50 but if I needed a one piece mount for a BMG I wouldn't hesitate a second to use a Badger.
They clamp tight without fucking up the optic, rings are SN'd and don't require lapping or any other work prior to use.