On a heavy kicking rifle I would avoid a variable power scope. There is not one of them that is as tough as a fixed power, or offers the long and constant eye relief. You are not varmit shooting. Moreover, being scoped with a .458 magnum would be a religous experience.

Don't get hung up on QD rings. If you carry a Leatherman (et al) you can remove almost any scope ring made in a hurry. The scope must be centered. I have used the Warne's twice and both times I had to crank in on the elevation adjustment until I was literally out of adjustment. No wonder there was problems with a 2.5 Leupold.