Anti cant leveling

"Way2evl"U.S. Optics Swivel. Pricey, but the best if you have picatinny rail.
You will be hard-pressed to find one. It would appear that USO had some design flaws and are replacing a lot of customer's levels. It would also appear that they can't keep up with the volume of replacements as well as new orders. I'm not sure if the replacements are any better/worse. I sent USO an email asking for the projected availability date, but haven't heard back from them.

This was quite disappointing to me as I really wanted one (and currently have one on "backorder"). I will be cancelling the order today, and am glad that you posted this question.
 
My preferred method is that I use 2 levels. I place one on the rail of the gun itself, which is hopefully a flat surface, and then place one on top of the elevation turret. I simply have the gun stay still by putting it on the ground and sticking a slew of towels on either side to prevent it from moving easily. Then once the gun is level I will go about leveling the scope and then tightening everything down. Then from there I will attach the bubble level while still keeping another level on the gun to make sure it is still level. Hope that makes sense.
 
Shine a flashlight through the scope, from the front. Place the gun so the back is pointing towards a wall, put a plumb line there or a piece of paper you have drawn a level line on. Adjust the scope level so it is level when the crosshairs are lined up with the line you drew. (The crosshairs will show up in the paper as a shadow) Then when the scope mounted bubble is perfectly level with the crosshairs, you can try and level it with the bore of the gun. Best way to make sure it is level is to use the box test.



Shoot a group and adjust a set amount of clicks down, then a group and adjust right, up, left and you should have a box, check it with a level and if it is straight you should be good. If it is not level, you need to loosen your scope and adjust it accordingly. Remember that your scope level is level with the reticle So use that when performing the box test.
 
"addertooth"Don't forget there are some scopes which have levels inside the tube. You can view your level without moving your face from ideal cheek weld and in context with viewing your image at the same time.
Depending on the scope manufacturer, some can't even properly align the reticle without cant. It would be really annoying if the bubble level inside the scope isn't perfectly aligned to the reticle.

To check the bubble level on a traditionally installed anti-cant device on the scope tube, simply open both eyes and check the level then proceed to close your non-scope eye while carrying out the shot. If you physically have to move your head or cheek weld to check the bubble level, you're probably doing it wrong.