Scope Mounting- parallel to the bore?

[H&R Glock]

Since my eyes no longer work correctly (old age) I have been on a scope buying binge lately
How can one make sure his freshly mounted rifle scope is properly aligned with the bore????(parallel)
It makes sense to me that if the scope is cross-ways to the bore that the scope can be adjusted to zero at say 100 yards, but shoot to the left of zero at 200 yards and the right of zero at 50 yards if the scope is not parallel.
Am I correct in my assumption or totally wrong, or do scope adjustments correct for this mis-alignment?
Yes my ears have failed too, but most of the other parts have not failed yet.

 

[TonyAngel]

My scope rigs are never parallel to the bore. I usually run a 20 to 40 moa rail. What’s important is to have your cross hairs squared.

 

[mcb]

Within the range of adjustment the scope has, it will align the optical path for you when you sight it. So yes a scope can compensate for a minor misalignments between bore and scope body. This is essentially what you are going when you sight in. The only time it becomes an issue is if you run out of adjustment before you get your point of impact where you want it.

There are scope mounts that will give you wind-age adjustment in the mount for dealing with a poorly aligned barrel to receiver/scope hard points. As TonyAngle also indicates there are scope mounts that purposely miss along scope in the with bore in the elevation plan for shooting longer ranges so you do not run out of elevation adjustment in your scope at long range.

 

[WelshShooter]

Scopes which are off axis to the bore (such as M1 Garand) when zerod at one distance would require a change in windage when shooting at longer distance due to the misalignment assuming zero actual wind. This misalignment is an inch or two. The misalignment from an off centre mount etc wouldn't have such an exaggeration compared with the former example.

Bore sighting your scope won't help you in this respect as you won't be able to distinguish between a mount which isn't straight with respect to the bore axis, off centre to the bore axis or a mix of the two. However, if its pretty darn close then you could assume the effect is minimal.

 

[MikeInOr]

Since my eyes no longer work correctly (old age) I have been on a scope buying binge lately
How can one make sure his freshly mounted rifle scope is properly aligned with the bore????(parallel)
It makes sense to me that if the scope is cross-ways to the bore that the scope can be adjusted to zero at say 100 yards, but shoot to the left of zero at 200 yards and the right of zero at 50 yards if the scope is not parallel.
Am I correct in my assumption or totally wrong, or do scope adjustments correct for this mis-alignment?
Yes my ears have failed too, but most of the other parts have not failed yet.

You are correct in describing what will happen when the scope is not directly above the bore of the rifle. I don't know how exact the scope to bore alignment needs to be considering that I can never hold my rifle PERFECTLY level (without scewing the scope .1mm to the left or right) even when I am on a bench rest. I guess the lower the scope is mounted (the closer the center bore of the scope is to the center of the bore of the rifle) the less effect a degree off of level will make.

In the real world I find learning to read the wind and compensating for it has a much bigger affect (for me atleast) than a exact perfect scope mount and having an exact level hold on the rifle.

Are you bench rest shooting at the 1000 yard range or hunting? I would not sweat any of this for a hunting rifle.

 

[H&R Glock]

I am aware of the radical elevation adjustment as I shoot a 50 bmg, but do not shoot it at the long ranges that require this drastic elevation change.
As Welch says the misalignment at shorter ranges are very small and should be just noted for personal horizontal hold over, but they are still there and affect my shooting without an easy solution.
It is my feeling that the accuracy of placement of receiver mounting holes (drilling) is what affects this misalignment the most.
This is a three dimensional problem in my mind that I cannot dismiss.
I hope some of you other shooters have mentally toyed with the problem and have an answer.
Wouldn't it be cool if someone would invent an optical device that plugs into the barrel that would accurately show 3 dimensional misalignment?

 

[jmr40]

What you are describing used to be quite common. They've made windage adjustable mounts for them for over 100 years. In fact early scopes did not have internal adjustments, you adjusted the mounts to zero the scope.

It wasn't until the 1960's that most all rifles were drilled and tapped for scope mounts from the factory and it wasn't unusual for the gunsmiths who did the work to have things out of alignment. Even many early factory rifles that were drilled and tapped were not perfect.

When using windage adjustable mounts you 1st center the cross hair in the middle of the scope. Then you adjust the mounts as you initially zero the rifle to ensure that the scope is in fact perfectly in line with the barrel. Once you get it pretty close to zero you can fine tune with the internal scope adjustment.


The base on the right goes on the front. A metal stud on the ring goes into the hole. When you mount the rear ring you adjust the 2 screws back and forth to get the scope aligned with the barrel. The stud in the front ring will pivot.

But modern rifles with today's precision machining will be straight and allow you to mount the scope parallel to the barrel without having to resort to this type of base. If your scope isn't parallel to the barrel then you either have a defective rifle or defective mounts that should go back to the factory.

 

[entropy]

My scope rigs are never parallel to the bore. I usually run a 20 to 40 moa rail. What’s important is to have your cross hairs squared.

Not all of us shoot 2000 yards. Unless you are, all you do by using a 40 moa mount is cut out about half of your vertical adjustment. Cross hair alignment is optimal when aligned verically/horizontally, but one can shoot a rifle with the scope turned 45 degrees and it will still be as accurate. Adjusting it might be a bit confusing for some......

 

[H&R Glock]

Thanks JMR40 you seem to understand my perceived problem. Thanks! Apparently the error inflicted in my three dimension problem is not sufficient to warrant my worry about the windage error that occurs at different ranges because of this misalignment. Perhaps the new breed of rails will alleviate a lot of my concern.
Scopes allow me to shoot better than I hear.

 

[Varminterror]

Windage adjustable bases and Burris Pos-align inserts in their Signature Zee rings are two options to correct parallelity.

But... at short range, the shift for an imperfect base/scope alignment is pretty negligible, and at long range, you’ll have spin drift to deal with even if you find a magic land of no wind, so don’t overthink perfection...