Objective way to level crosshair

[ralfus]

A lot of folks worry about leveling their scope without wondering if the rifle is level.
This comes in handy - Magnetic Angle Finder It's not expensive at $5. You can place a straight edge across the base(s) under the scope and make sure the rifle is level and then put the level on the top turret. There may still be some error in the erector assembly but it will get you close. The angle finder listed makes it rather easy to read 1/2 or even 1/4 degree errors. the needle bounces a little but will dampen after a few seconds. Another way to compare is to level across the base prior to scope mounting and compare level to the front or rear sight bases. If they are the same then you can us the sight base to compare level to the scope once its mounted.

Edited to add: I just realized that I resurrected a 5 year old thread.

[fj40mojo]

I found my old post and copied and pasted this.

My method for mounting a scope and aligning the reticle is as follows. First I assume that the bottom of the action is perpendicular to the bore. That being said I remove the barreled action from the stock and place it on a level surface with the action supported on a pair of precision ground 1-2-3 blocks and I use a machinist jack set to support the muzzle end of the assembly. With the scope loose in the rings and as close as possible to the location I want it to be for proper eye relief I can rotate the scope within the rings and use a machinist set up square indexed of the same level surface as a vertical reference line. Line the vertical crosshair up with the vertical edge of the square and you are plumb. I've tried putting spirit bubbles on the tops of the reticle caps and on the reticle itself and it's never worked out, at least not to the level of precision that I'm after. I prefer to use machined surfaces to reference off of when trying to maintain parallelism and perpendicularity. All these tools can be purchased from MSC or Enco for less than what you 'd spend on most of the scope leveling gadgets that are on the market.

My ideology here is that the goal is to align the reticle vertically with the bore. I find a machined surface somewhere on the bottom of the action (whether that is the recoil lug or the actual bottom of the action) and use a precision ground block to support the action. This means that my action is now in a parallel attitude with my reference surface. Then I'm using a precision ground tool (square) to establish a vertical line from the same reference surface that I then align the vertical crosshair with. Everything is referenced off of the same surface and a machined surface of the action. It works for me, and as a machinist it makes sense to me to use the same techniques an inspector would use. If I had a 100yard long granite surface plate I would use that, but to my knowlege no one has one of those. It's not as complicated as it sounds and the tools are inexpensive and accurate.

[ralfus]

Good idea. I've removed the stock and it works well on a Mauser or winchester 70 but on a round receiver your only assuming the recoil lug is machined square and level on its bottom surface and wasn't canted when the barrel was torqued. I like your idea of using a square as a vertical reference. I'll have to try that.

[fj40mojo]

Originally Posted by ralfus

Good idea. I've removed the stock and it works well on a Mauser or winchester 70 but on a round receiver your only assuming the recoil lug is machined square and level on its bottom surface and wasn't canted when the barrel was torqued. I like your idea of using a square as a vertical reference. I'll have to try that.

I've had to use the recoil lug only on Rem 700s and Model 7s, and it worked fine. All my other bolt guns have some sort of machined flat surface on the bottom of the receiver that provides a good reference.

[jerrschmitt]

I level my rifle first with a small level then I level the scope with a plumb bob but none of that is final proof. I go to the range and sight in the rifle and then raise the elevation knob 20 or so min and see if I have a pumb line from that group to the first group. If not, somethng is out of plumb.

[Forester]

Originally Posted by jerrschmitt

I level my rifle first with a small level then I level the scope with a plumb bob but none of that is final proof. I go to the range and sight in the rifle and then raise the elevation knob 20 or so min and see if I have a pumb line from that group to the first group. If not, somethng is out of plumb.

+1

All the versions of eyeballing it leave a degree of imperfection, get it close this way and then go to the range and shoot, if it tracks straight, or in the case of the OP holds over straight then it is straight. Its the ONLY way to be certain.

[fj40mojo]

Yes, this is for initial set up. Nothing will replace actual at the range verification of true plumb by shooting "the box".