Standard base or 20 moa

ShtrRdy said:

I would definitely put a 20 moa rail for that combination.

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bruce_ventura said:

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.

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Mcarso1 said:

You guys run the leveling bubble in the base generally or top ring? This is my first longrange build so pardon the stupid questions.[/QUOTE

I like the top half of the ring.

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ShtrRdy said:

I like the type that clamps onto the scope tube so that I can see the bubble without havinng to move my head. Plus my old eyes can focus on the level when it's further away.

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Mcarso1 said:

getting ready to pickup nightforce ATACR 5-25/56 Saturday mounting on Christensen arms ridgeline 6.5x284. Would you still go with 20 moa rail with this scope ?

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Greyfox said:

It really depends on the range you are planning to shoot. A 20 MOA base is my preference when setting up my LRH rifles, but, the ATACR will easily handle any hunting shot (out to 1200 yards) without optical compromises with a 6.5x284, and using a standard base.

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Mcarso1 said:

What height rings should I get for the 56mm objective to keep it as low as possible?

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