Mount for Scope Cant or Reticle Cant?

When mounting a scope you should level your rifle, and then level the scope in the mount/rings. However, reticles are not always straight up and down with the scope. Very expensive optics (Nightforce, for example) have quality control around the amount of reticle cant that is allowed to leave the factory - let's say <1 degree. More affordable optics may have a higher tolerance of 3-5 degrees of reticle cant. Let's ignore the 'simple' answer of buying a $2k scope...

In this case should you mount for proper scope cant (i.e. use a bubble level on top of your elevation turret) or should you mount for reticle cant (i.e. hang a weighted string 25-50yards out to ensure exact vertical alignment of the reticle)?

Trying to see if I'm off base here. I'm thinking you should mount a BDC or holdover-type scope with the reticle straight up and down. Other scopes like a simple cross hair should be mounted for a level scope, even if the reticle is a bit off?

I just use a door frame or window for plumb, but I don't have anything fancy.

This video and article may not answer all your questions but i found it useful for mounting scopes using reticle cant.

EXD Engineering Vertical Reticle Instrument can be purchased at Brownells but you don't need it to project the reticle on to the wall, you can use cardboard or painters tape to block the light.

I took a shallow lid from a box that once held Lindt Master Chocolates. I drew a square inside the lid. I then drew a diagonal line from one corner to the opposite corner, which I'll call the main line. Then I drew a series of parallel lines in three colors on each side of the line.

Place the butt of the rifle snug into the corner. Assure that each side of the butt is centered, using the parallel lines as guides.

Shine a flashlight into the objective, casting the image of the reticle onto the lid. Rotate the scope if needed until the verticle "hair" agrees with the drawn main line.

I learned over the years that the top turret is not a reliable perpendicular base. Not in scopes affordable to the average bear.