It's not so simple CatShooter.
For one, a level gun is relative.
That is, my T2000 was set up level at 7deg of cant, one of your guns could be bedded with a degree or two of cant w/resp to various reference points.
Doesn't matter how the gun is rotated provided it recoils right & you get back to it with every next shot.
You shouldn't rely on turret tops, cross hair level, bases, action flats, or stock flats -while every bit of it is separate from scope elevation adjustment, or worse, it results in bad handling.
Where the ScopLevel is set plumb to a mounted scope elevation(tested via POI through the range), you can move the scope from gun to gun and it will always be right. You just get another gun in the bags right, set the scope with calibrated ScopLevel on rings so it indicates level, torque it down, reset your zero.
With this you can then dial the scope up 30moa, and no matter how hosed up 3 or 4 other levels(if mounted) might read, the gun will shoot straight up 30moa(well, if your scope is true MOA)(few are).
The more potentials between elevation adjustment and the level measuring, the greater the disconnection to what I'm talking about.
Some folks level their rest, or barrel, or action, or bases, or rings, or turrets. There is the Level-Level-Level system out there. But all are further from level than provided off the tube and calibrated to actual elevation adjustment -with the gun in any position that handles best.
As a plus, your shooting eye is centered behind a ScopLevel while in shooting position. No viewing from off angles with an off eye.
For those who need a plumb cross hair as well as elevation adjustment(wind hold-offs), all you can do is test to find out if you're lucky enough with that. If unlucky, I don't see how it could be fixed. One or the other then.