No longer have it, but the best leveling system I had going was out my backdoor when I use to have a range and backstop. I had a plumb line at the backstop, and I had a universal holding fixture that mounted upon a 3-foot square cement pad at the firing line. I'd hold the barreled action plumb and square in the fixture and then use the plumb line at the backstop to square the scope reticle. This system was always quick and simple, no fuss and no muss, everything was square to earths gravity. I saved the little portable gizmos and techniques for making a quick fix when afield. Even then, having some form of small reliable level, that easily fit upon the surface of the action, while it was held square in a makeshift fixture, when combined with a simple high contrasting string plumb bob, hung at a distance, makes for a very easy to use travel setup which is pretty darn accurate when mounting scopes on the go.
