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Different Readings.
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Tik View Drop Down
Optics GrassHopper
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    Posted: October/07/2019 at 11:03
Hi Guys
I have 2 scopes from the same manufacture.  When mounting them on the same gun with the same 1 piece mount. I am getting a horizontal zero/grouping difference of 2 Mils between the 2 scopes at 50m's. The top rings are torqued down and have the same space either side. On mounting I just undo the top rings and drop the scopes into position. Nothing else is moved. 1 scope has perfect optical and mechanical zero and the other only out optical by .3 mils to it's mechanical zero.
I have repeated this twice with the same results.
Does anyone know why or how there can be the 2 mils difference. Both scopes are First Focal Plane.
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Rancid Coolaid View Drop Down
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I'm not sure I see why it matters, can you elucidate?

Are you saying when zeroed on the same gun with the same hardware, both scopes differ from their mechanical zero by 2 mils?

Comparing absolutes between 2 mechanical devices is difficult. If both scopes hold zero and both scopes track true, why does it matter if they are both at different spots in their mechanical range?

This is why scopes have adjustments, because few things are absolute in the system, and they have to reliably adjust to point of impact.

That they are from the same manufacturer doesn't really matter. In fact, they could be exact same model from same manufacturer and it still wouldn't matter. What matters, in my opinion, is what each scope does when mounted to the rifle: does it track, does it hold zero.

The adjustment limits aren't meant to be quantitative in most meaningful ways, just the adjustments themselves. Everything has a tolerance, and I think you are measuring something they didn't expect you to measure.

If they both shoot true, you are welcome to spend time trying to understand the "why", but it'll be purely academic.

If one or both does not track or hold zero, the conversation is very different.
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Hello Rancid Coolaid 
Thank you for your time in answering my question.

Both scopes hold zero however
Scope 1 has a total adjustment of 18.6 mils which is 3.6 mils more than its quoted specification of 15 mils. However it is spot on for the optical and mechanical zero. To zero it with the rifle I have to come 4.9 mils to the left which eats up half of the adjustment.
Scope 2 has a total of 15 mils adjustment which is its quoted specification. Optical zero is .3 mils right of mechanical zero. To zero the rifle I have to come 2.9 mils left which eats up 1/3 of its adjustment.
Scope 1 is the scope I wish to pair with this rifle and shoot it out to 1100 yards. Scope 2 is going on a slightly better rifle. I was trying to understand why I had such a large error on the 1st scope and why an extra 2 mils compared with the second scope.
I have high end scopes and high end mount so would have thought they would have been the same. I am trying to understand why I am getting the figures I have. 
It may be that I am concerned about nothing but I am new to the workings of scopes and just thought that 4.9 mils was a large amount. Especially when that works out at 24.5 cm's at 50m's or 4.9 m's at 1000m's from where the bore of the rifle is pointing.
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koshkin View Drop Down
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What are the scopes?

It is not uncommon to have a difference between scopes and it can come down to a variety of different things.  Usually, it is some sort of a ring misalignment that effects the two scope tubes differently, but not necessarily.

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koshkin View Drop Down
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Also, what gun is this on and what type of base/ring arrangement are you using?

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Optics GrassHopper
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Hi Koshkin
 Scopes are IOR Recon and Crusader and fitted to Tikka T3 Tac A1 with a solid 1 piece 20 MOA mount.
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Optics GrassHopper
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I think I can rule out misalignment.
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Rancid Coolaid View Drop Down
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A 20 MOA base is about 6 mils, so anything going on that base should get you back most of that 6 mils. That should be calculated into your deviation from scope's middle adjustment point, though - again - I'm still not sure it matters much.

Tikka makes a good gun, what caliber?
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Originally posted by Tik Tik wrote:

Hi Koshkin
 Scopes are IOR Recon and Crusader and fitted to Tikka T3 Tac A1 with a solid 1 piece 20 MOA mount.

IOR's are not known for manufacturing consistency.  I stopped testing IORs quite a while back partly because of that inconsistency: I can't make recommendations if I do not have faith in repeatability of the product.

Given what you are trying to do, you are expecting too much from your scopes.

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you got that right. I had a 3-18x IOR and when zeroed i had 3ish mils left on the right side.  Had i cranked way over to get that zero   I called valdada and they let me return it. The sent me a replacement, same model. It was much closer to the mechanical zero when zeroed. 
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Originally posted by Rancid Coolaid Rancid Coolaid wrote:

A 20 MOA base is about 6 mils, so anything going on that base should get you back most of that 6 mils. That should be calculated into your deviation from scope's middle adjustment point, though - again - I'm still not sure it matters much.

Tikka makes a good gun, what caliber?

How does the vertical 20MOA affect the horizontal? Gun is in 6.5 Creedmoor.
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Optics GrassHopper
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Originally posted by supertool73 supertool73 wrote:

you got that right. I had a 3-18x IOR and when zeroed i had 3ish mils left on the right side.  Had i cranked way over to get that zero   I called valdada and they let me return it. The sent me a replacement, same model. It was much closer to the mechanical zero when zeroed. 

Did they offer an explanation and how close was the second.
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Sorry, I reread the second post and saw you were talking about windage adjustment. You are correct, the 20MOA base gets you no windage back.

Your rifle and caliber are solid, IOR has a long and troubled past with scope quality.

If they hold zero and track true, you have to decide if the windage issue is enough to make you move to another brand. 
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Originally posted by Rancid Coolaid Rancid Coolaid wrote:

Sorry, I reread the second post and saw you were talking about windage adjustment. You are correct, the 20MOA base gets you no windage back.

Your rifle and caliber are solid, IOR has a long and troubled past with scope quality.

If they hold zero and track true, you have to decide if the windage issue is enough to make you move to another brand. 
Yes they track true and hold zero. I am just trying to get to the reason for difference. Not really wanting to change scopes.
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As Koshkin said, it could be many different things, and further complicated by the brand being known for inconsistency.
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No explanation.  This was over 10 years ago, so I don't recall exactly where is was, I just remember is was much closer to the middle. 


I have never been one to worry or care how close a scope is to the mechanical zero.  As long as I have enough adjustment to compensate for the type of shooting I am doing with that rifle/scope combo there is really no need to care.  Some people go to all the trouble to set their scopes to the mechanical zero before mounting them.  Why.  There is only a small chance it will stay at that mechanical zero.  They are not meant to, that is why there are adjustments.  There is just no reason to worry about it unless it is affecting your shooting. 

Lifetime warranty and excellent customer service don't mean a thing when your gun fails during a zombie attack.

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Optics GrassHopper
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Originally posted by Rancid Coolaid Rancid Coolaid wrote:

As Koshkin said, it could be many different things, and further complicated by the brand being known for inconsistency.

Don't take this the wrong way and I am valuing your input.
I hear a lot of people stating that IOR scopes are inconsistent or rubbish. However they generally don't back this up with fact. Nearly all the comments come from America and not Europe. Yes there is 1 or 2 but that is the same with S&B, Vortex etc. But it seems that it's always someone they know and not the person who owns the scope. 
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Originally posted by supertool73 supertool73 wrote:

No explanation.  This was over 10 years ago, so I don't recall exactly where is was, I just remember is was much closer to the middle. 


I have never been one to worry or care how close a scope is to the mechanical zero.  As long as I have enough adjustment to compensate for the type of shooting I am doing with that rifle/scope combo there is really no need to care.  Some people go to all the trouble to set their scopes to the mechanical zero before mounting them.  Why.  There is only a small chance it will stay at that mechanical zero.  They are not meant to, that is why there are adjustments.  There is just no reason to worry about it unless it is affecting your shooting. 


Thanks and I think you are probably right and I am only caring about it from a perceived shooting of a 90 degree 25 mph wind at 1100 yards. Which is probably not likely but you never know.
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If you shoot on that day with that gun in those conditions, the scope will only be a minor player in a very dramatic play.
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Adjust for drop, hold for wind with the reticle.
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