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How much importance do you put on the optical center?

 
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  #1  
Old 04-21-2014, 01:04 PM
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Join Date: Sep 2011
Posts: 2
How much importance do you put on the optical center?

Hi All,
Thank you for taking the time to read my question.
This is to all of you experienced long-range shooting gurus out there.

How much importance do you put on the optical center?

On my rifle and scope set up, (338 Lapua and a Vortex Viper PST) if I preload my MOA to 30 using an aftermarket base, at 100 yards zero I would only have about 5MOA to spare, my scopes optical center should be around a thousand yards. Then to take it up to its maximum I would be out to about 1600 yards.

The same scenario but with the preloaded 20 MOA should give me about 15 MOA to spare at 100 yards, the optical center is now closer to 800 yards and my maximum zero is out to about 1400 yards.

In your opinion would you set up your scope for maximum distance (Preload 30MOA)?
Or
Would you set up your scope closer to optical center where you're going to use it 99% of the time and then rely and hold over for those once in a while shoots (Preload 20MOA)?

Thank You!
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  #2  
Old 04-21-2014, 01:54 PM
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Join Date: Dec 2008
Location: Great Falls, MT
Posts: 4,942
Re: How much importance do you put on the optical center?

Yes, here's the best answer I've seen courtesy of Bruce ...

Quote:
Quote:
Originally Posted by bruce_ventura View Post
Even though the scope adjustment range may be large enough to get to 1,000 yds, you should use a 20 moa base. That's because off-axis optical aberrations that degrade resolution increase with incidence angle. You should set up your rifle so that the incidence angle is minimized for long distance shots (where resolution matters most).

Assume the base is within +/-10 moa of alignment with the rifle bore. Let's also assume your bullet drops no more than 30 moa at 1,000 yds, and you like to zero your rifle at 100 yds. With a standard base, you would need up to -40 moa of adjustment to get to 1,000 yds. That means you need a total 80 moa of adjustment.

With a 20 moa base you would need up to -20 moa to get to 1,000 yds, but up to 26 moa to get to a 100 yd zero (worse case boresight alignment in each case). That means you need a total 52 moa of adjustment. With a 20 moa base, however, the incidence angle at 1,000 yds is 20 moa less, so the image will have less blur.
BTW, welcome to LRH and enjoy!
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  #3  
Old 04-21-2014, 07:20 PM
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Join Date: Sep 2011
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Re: How much importance do you put on the optical center?

Thank You Feenix!
I do appreciate your quick reply, this is exactly what I was looking for.
Have a great week!
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  #4  
Old 04-21-2014, 07:26 PM
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Join Date: Dec 2008
Location: Great Falls, MT
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Re: How much importance do you put on the optical center?

Quote:
Originally Posted by Frankjr7 View Post
Thank You Feenix!
I do appreciate your quick reply, this is exactly what I was looking for.
Have a great week!
... and to you as well, cheers!
__________________

I voted for my "FREEDOM", "GUNS", and "MONEY" - keep the change - UNK.



"I am always proud of my country!"

"Leadership Rule #2: Don't be an @zzhole." - Maj Gen Burton Field.
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  #5  
Old 04-21-2014, 07:41 PM
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Join Date: Jan 2011
Location: Spokane, WA
Posts: 2,632
Re: How much importance do you put on the optical center?

Bruce always teaches well. I was not aware of this either. Thanks Feenix!
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