Scope unstable at bottom of adjustment?

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propliner

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I've been testing a new rifle with a brand new Nightforce ATACR. It's a 120moa scope and I have it set up with a 60moa rail/mount combo so that when zeroing at 100 yards I have it dialed to its bottom most adjustment.

At this setting I'm getting 2" wide groups with shots walking left and right. The vertical is well under an inch. If I dial it up 15moa the groups tighten up considerably to nice round sub-moa groups.

I'm pretty sure the scope has unstable windage at its bottom limit and I am quite disappointed. Also, the clarity suffers considerably. These are not problems I expected from a higher end Nightforce.

Has anyone else seen this problem?
 
Maybe don't dial your scope to the extreme edge. Have you tried that? You do do know that there is not a single scope in existence that will perform well when you crank the ever living daylights out of it, right? You're not experiencing a problem. You're experiencing a design limitation inherent in the design of rifle scopes, one that cannot be remedied without artificially limiting performance.
 
Experienced that problem with other brands. Burris recommends to have windage and elevation adjustments at or near the mid point of adjustment ranges for best results otherwise optical distortion and other problems result. I thought high end scopes might be less prone to this problem?

 
Not to sound obvious, but you are using a 60moa rail on a scope that theoretically has 60 moa of depression.

Not allowing for any misalignment between bore, mounts and scope, that is a hard task to accomplish.
 
propliner said:
I've been testing a new rifle with a brand new Nightforce ATACR. It's a 120moa scope and I have it set up with a 60moa rail/mount combo so that when zeroing at 100 yards I have it dialed to its bottom most adjustment.

At this setting I'm getting 2" wide groups with shots walking left and right. The vertical is well under an inch. If I dial it up 15moa the groups tighten up considerably to nice round sub-moa groups.

I'm pretty sure the scope has unstable windage at its bottom limit and I am quite disappointed. Also, the clarity suffers considerably. These are not problems I expected from a higher end Nightforce.

Has anyone else seen this problem?
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Hitzy said:
That's a great way to destroy your scope BTW...
Not a scope issue here, 100% user error.
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I agree. Reset the scope reticle to center,remount the scope checking for level between rifle and scope,"ZERO" with a laser bore-sighter,take it to the range for fine tuning.
 
Your mounting system has so much built in elevation that you are winding the scope to its limit trying to get a 100m zero.
You are setting the thing up for extreme long range shooting?
If you must come up 15moa to get round groups, a 40moa base should solve your problem.
 
It is quite common to mount scopes in a way that maximizes mechanical elevation in the ELR game. I definitely wouldn't call it user error only. In my limited experience, some scopes handle the extremes just fine- others, whether optically or mechanically, just can't hack it. I know it's disappointing to have to leave some elevation on the table, propliner- but maybe try mounting your scope in a less extreme base/ring combo?
 
I'll have to use the scope without the 15moa mount and just the 45moa rail. And yes, I was trying to set up the rifle up for ELR shooting for 2100m. If this scope can't handle the elevation adjustment at the bottom then I'm pretty sure it won't handle it at the top either. These scopes are supposedly built to be able to use the full range so "user error" does not apply here.

My Tangent Theta accomplishes this task perfectly and has a crystal clear picture at both ends. I suspect Nighforce sells scopes based on big numbers rather than actual performance. Perhaps I'm just a fool for expecting it to to succeed.
 
propliner said:
I'll have to use the scope without the 15moa mount and just the 45moa rail. And yes, I was trying to set up the rifle up for ELR shooting for 2100m. If this scope can't handle the elevation adjustment at the bottom then I'm pretty sure it won't handle it at the top either. These scopes are supposedly built to be able to use the full range so "user error" does not apply here.

My Tangent Theta accomplishes this task perfectly and has a crystal clear picture at both ends. I suspect Nighforce sells scopes based on big numbers rather than actual performance. Perhaps I'm just a fool for expecting it to to succeed.
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How much $$ was the TT over the NF?
 
My thought is if you're going for long range anyway, zero out at 400 or something and not use the bottom of the adjustment. But your loss of confidence in the top of the scale is then valid too I suppose.
My ATACR doesn't exhibit this problem.
 
Hitzy said:
How much $$ was the TT over the NF?
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At the time, it was $600 more. I should have bought 5 of them. Everyone else should have, too.

Dmay said:
My thought is if you're going for long range anyway, zero out at 400 or something and not use the bottom of the adjustment. But your loss of confidence in the top of the scale is then valid too I suppose.
My ATACR doesn't exhibit this problem.
Click to expand...

Thanks for the sensible real-world experience and advice. I'll try zeroing at 400 and 500m and see how it works out before going any further.
 
Don't know what caliber you are shooting, but if you have to come up 15 minutes to get round groups, what would the base zero be with 15moa?
 
It's a .338 Norma Mag. I was looking for a base zero of 200m and the ability to dial up to 2100m. Missing the 15moa mount and still zeroing at 200, I'd be good for 1950m if the upper limit works out. Not a huge loss, I suppose.
 
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