Reticle to Bore Perpendicularity

[joedirt199]

Or you coud hang a mirror from the ceiling and look through the scope into it. Rotate the scope till the reticle is straight through the scope and bore exit.

[triggerjerk]

Hang a plumb line from the door knob. Set a bench, a chair or whatever a couple of feet from the door. Bag your gun firmly with the butt stock towards the door. Get a piece of flat metal and a small line level. Put the metal across the gun on your pic rail sticking out so you can put the line level on it. Make sure it's square across the gun. I'll often push it against a ring and call it good. Level the gun crossways. Shine a flashlight through the front objective lens. It's got to be damn near stuck in through the front objective. It will cast a shadow of your crosshairs against the shadow of the plumb line. Rotate scope until vertical crosshair shadow is parallel with the plumb line shadow. Verify gun is level. Verify crosshair parallel to the plumb line. Continually verify level/parallelness as you tighten screws. Best way to level, I'll have a spacer that I will put inside a receiver that has flat bolt raceway and that spacer lifts my flat piece of metal up to stick out of receiver, and I put my line level on it. Again, make sure the level is square to the rifle. If it is angled forward or backward and the rifle isn't level lenghtwise, you won't have rifle level crossways.... I will sometimes mark eye relief by putting a piece of tape or pencil line next to the rings so that as you rotate scope you don't pull scope too far forward or backwards....

[Coal Dragger]

Just spend $500 on a Spuhr mount.

They include leveling wedge to level the bottom of the erector housing on the scope with the mount/rail.

Works great!

[Coal Dragger]

Or buy this for $38.00 plus shipping…

https://arisakadefense.com/optic-leveler-combo/

[triggerjerk]

That looks like the affordable easy button for all but the most demanding shooters.....

[georgeib]

I use a couple of bubble levels I bought from Midway. One on the receiver and one on the scope, tighten everything down, verify, and it's good to go.