what is the correct way to find the optical center?
If you run the adjustment all the way left to right or up and down and have 4 revolutions of the knob, is the center at 2 revolutions?
i read or heard that you can use a mirror. you will see two sets of crosshairs and adjust untill they overlap each other?
what is the best was to tell if a scope tube is bent?
Thanks, Dave

The old "turn it all one way and count the turns, turn all the way back and divide in by two works fine.
You can also check to see if they are centered by notching a small box and setting the scope in the notches, and aline with a "target". Now rotate the scope in the notches without moving the scope or box and see if the crosshairs remain on target. If they move adjust until they stay centered.

hope this helped............

By turning the knobs to the middle position you only have the "mechanical" center. Leupold told me how to do the optical center using the mirror and it does work and it gives a true "optical" center.

quote:

Originally posted by Jim Kobe:
By turning the knobs to the middle position you only have the "mechanical" center. Leupold told me how to do the optical center using the mirror and it does work and it gives a true "optical" center.

So, are you going to share what Leupold told you, with the rest of us? That was the original question here, i.e., "How do you do it correctly?"

I would sure appreciate hearing what the old Oregon Beavers up in Beaverton have to say, as would probably many others..... Thanks <G>

thanks, Joe, jim
I have a leupol 2-7x vari-xII that is giving me fits .
I am mounting it on a model 70 1965 vintage
using tw0 piece low mount leupol bases. i have lapped the rings. there is not much adjustment with this scope. 4 revolutions of the turrent from top to bottom.
At first i thought the tube was bent.
I tried to use a mirror and the cross hairs will not over lap? not sure that I am doing it right. I fitted a shim under the rear base it took .020" to get with in 6" of center on my bore scope.
I am afraid this would put to much stress on the scope.
next option will be to mill the front base.
Havent desided yet if that is the answer.
any suggestions or thoughts greatly appriciated. should have stuck to burris

This is a relly neat way to do it and I wish I knew how it worked. Place the objective lens against a well lighted mirror. The bathroom mirror works for me. You may have to adjust for eye relief, but if yo look into the scope, you should be able to see the reticule and a shadow of the reticule. Adjust the windage and elevation so the two coincide. There you have it.

Jim

Will someone explain to me the purpose behind finding the optical center of a scope?

copyied this from the OUTDOOR writer
http://www.theoutdoorwriter.com/shooting/about_scopes.htm
I noticed this with one of the rifles, as I cranked on my vertical adjustment, I got some weird windage shifts. the erector assembly is not even close to optical center, and the erector tube is riding against the scope body tube. The erector assembly is a tube within the scope. When you look through the scope and center the crosshairs on a target, you are really looking through the erector tube, which together with its collection of lenses, is often called the erector assembly. As you adjust the windage and elevation, you are really tilting the erector tube up, down, right, or left, which explains why crosshair is always constantly centered.

That's a good article. But I still don't see what is accomplished by finding the optical center of a scope? Should that be done before mounting a scope? Why do it.

this is what i think>
The base should be the same height level.
the rings should be the same.lapped if necessary
The scope should be mounted as low as it can with out touching (only ring contact)..
at this point the scope can be mounted into a stress free mount. a stress free scope that is optically centered mounted in a stress free mount adds up to good tracking and when you get out to 5 or600yrds, will make all the diffrence
i mount the scope as close as i can to being on target with out using any internal adjustments
So to sum it up Stress Free Stress Free

prewar, Things tend to stay aligned better if they are not cranked to the limits of their travel. If you are using good bases like Leupold or something and you have it (the scope) optically centered then you can tweak with the rear mount and be nearly centered on target before you need to even touch those delicate little internal adjustments. Same goes for elevation and lapping in your rings. A stress free scope is a happy scope. Jim

i just mounted a nikon 6x18 on a rifle that i'm planning on using as a long range (6-700 + yds) varmint rifle. When i mounted them, the scope was optically centered, however when i boresighted it, i had to crank the elevation knob up and the windage to the left. I would say that i cranked the elevation knob probably about one full revolution. Now that it's shooting where it should be at 100 yds, i want to move on out to 200, 300, 400, 500, 600, 700....however i do not want to run out of elevation adjustments via the scope. Since it's already a full revolution up, how can i extend my range of adjustments? IE, how can i tweak the bases (other than getting a long range base) can i get them adjusted to be as close to optical center of the scope as possible? Thanks guys
Ruck

Ruck, You kind of missed the part about tweaking the bases. Don't move the internal adjustments until you get it close, at least on paper. If you are hitting 5 or 6 inches to the left then you need to move the rear of the scope on the base to the left until you get it close. Very close. Only then do you start playing with the internal adjustments to "fine tune" Like I said earlier you need to start with quality bases that are adjustable for windage. If you are using Weaver or whatever, what you see is what you get. If you are running out of room vertically then you need to lap the rings or get a set of bases made for mid or long range. Jim

One thing you should know is that on some, if not all Leupold scopes, there is more adjustment from center in one direction than the other.

You can call Leupold and they will tell you how many moa's are left and right of center.

Ruck,

You can get more elevation with the Burris rings that allow the use of different size inserts for the front and rear rings.

These inserts are supplied by Burris.

This also eliminates the need to hone the rings and does away with ring marks.

The mirrow thing is good and it works, but if the gun is on a rifle, then the old go all the way and come half way back still works well enough for Government work....

The idea is to have your scope with equal or close to equal adjustment in both directions with a fixed mount or any mount for that matter..especially on a G&H QD sidemount and by having the cross hairs in the center of the focal plane you also releave stress on the scope and it tends to hold zero better and return to zero is better..in fact everything is better with a scope in its center focal plane.

Ray and others, all that makes sense having a scope be centered optically or mechanically internally. Most of my scopes are in Talley rings and bases, so my only means of adjustment for windage is the scope turret. I always mount my scopes as close to the barrel as possible and not being a long range shooter I've never run out of elevation. So with fixed Talley type rings, I'm guessing one doesn't have much of a choice in keeping a scope centered optically unless you get lucky.

Pre war,
I have all my bases machined so that the scope is bore sighted at 100 with the scope in its focal plane..It doesn't cost much and its a one time shot...

But, since most of my guns are Mausers and I have them surface ground to start with, they come very close with Talleys out of the box. and if not I have the bases fitted.