I use a Tipton Standing Ultra Gun Vise. I level the rifle by using a level on the picitiny rails which are either machined into the receiver (Lone Peak Arms and BAT actions) or screwed to the receiver (Tikka actions). All you need to worry about is left/right square. I then attach the Wheeler scope mounting barrel level tool to the barrel making sure the two levels match. I now can remove the level from the rail and know that the rifle is squared through the mounting process. Attach the bottom rings to the rail. Lay the scope into the rails with all caps, zero stops etc removed so that you can put a level directly on the erector. Slide scope forward or back to set eye relief. Level the scope to the barrel level. Tighten the screws on the top rings going slowly back and forth between the screws to make sure there is even torque keeping the scope perfectly level. You can now check the reticles. If the reticles are not squared you have a scope with a manufacturing defect.
Of all the scopes I have mounted, mostly Swarovski, Zeiss and ZCO I have had only one with an off kilter reticle. That scope, a Zeiss V6, was sent back to Zeiss. Zeiss checked and everything on the scope was in proper working order but the reticles were indeed off, by 1%, according to the technician. Even though 1% is within the Zeiss tolerance range they agreed to send me a new scope and check it before shipping. Needless to say I am very impressed with Zeiss's customer service.
