How do you figure what height rings you would need for a particular scope and rifle? Example, I am getting a 8-32x44 for my weatherby vanguard, I have medium height rings now that are 1" I am getting a scope with a 30 mm tube so I have to change rings.The scope I have now has a 40mm objective. So, without bringing the whole shooting match to the gunshop is there a way to know for sure if I can go with the low rings? There is just under 1/2" between the barrel and the objective of the scope I have now.