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First Focal Plane Vs. Second Focal Plane

 
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  #71  
Old 03-05-2013, 06:24 PM
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Re: First Focal Plane Vs. Second Focal Plane

Quote:

I gave you one but I will elaborate.

A 8~32 NXS has 65 total moa of internal elevation. You mount it with a common 20 moa rail. This gives you 50 +/- moa of elevation dial up. Your reticle on full power is 20 moa for a total of only 70 moa. There is a rock ledge at 2100 yards with a visible dark spot that is screaming at you "come on, try me" your 338 LM with a 300 Berger needs 81 moa. You are short by 11 moa. But you have the option to dial back to 16x and now you have a total available moa up of 90 moa.

Not common, but yes it is a fact and I have been it that position before.

Jeff
That is the exact reason i chose the vortex 6-24 pst SFP, it has 65 MOA in adjustment and 10 in the reticle at 24x, if i back it off to 12x i have 20, 8x 30, and 6x at 40. The magnification ring has those spots marked on it and you turn it and you can feel a distinctive little stop where you need to be. My 284 win with the 162 A-Max will need about 75 MOA up at 1800 yards, so i will back it off to 12x and dial 55 MOA and use the bottom hash mark as a hold.

Riley
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"Firearms are second only to the Constitution in importance; they are the peoples' liberty's teeth."
~George Washington

"The only advantage a light rifle has is weight, all other advantages go to the heavy rifle."
~ JE CUSTOM

"Dope that scope and tickle that giggle switch"

~Doublezranch

Biggest fail of 2014 so far... http://www.longrangehunting.com/foru...ea-ftf-128972/
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  #72  
Old 03-05-2013, 06:43 PM
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Re: First Focal Plane Vs. Second Focal Plane

I encourage you to test that extensively when your scope arrives.

Most optics actual magnification does not precisely match the indications printed on the ring. Some not even close. So you must "calibrate" the magnification ring to the reticle. Here's an article that describes the process. (one method anyway)

How to Optically Check a Rifle Scope

Last time I did this test, we did it on a nightforce, leupold, vortex, bushnell, and a few other scopes. NONE lined up where they said they would be. Even those that did, the numbers had no "tick" marks to line up perfectly. As Broz pointed out, nightforce has a little "tick" line that lines up with their indicator at half power. Yet I would be very surprised if those are dead on either. The one we tested wasn't.

The best way to do it is to calibrate it, and put precise markings with little needle scratches. Then, if you confirm them to be correct, engrave them. Once it's calibrated, it's set for good. (provided the optic is quality and the reticle isn't moving around inside the erector)

EDIT: See this is what I'm talking about. Why wouldn't they design that reticle so that the holds continue down the entire stadia? Why stop it at 10 moa and go to a big thick black line? They could give you a lot more holds in that FFP to equal the holds you'd have available in the SFP if they just built the reticle differently.
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  #73  
Old 03-05-2013, 06:50 PM
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Re: First Focal Plane Vs. Second Focal Plane

Yup. It's a lot simpler for a manufacturer to put a mark on a magnification ring than to calibrate it to ensure the mark is at the exactly correct location. Same with turret adjustment values. They ought to be tested before they're accepted as correctly advertised.
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  #74  
Old 03-05-2013, 06:51 PM
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Re: First Focal Plane Vs. Second Focal Plane

Quote:
Originally Posted by orkan View Post
I encourage you to test that extensively when your scope arrives.

Most optics actual magnification does not precisely match the indications printed on the ring. Some not even close. So you must "calibrate" the magnification ring to the reticle. Here's an article that describes the process.

How to Optically Check a Rifle Scope

Last time I did this test, we did it on a nightforce, leupold, vortex, bushnell, and a few other scopes. NONE lined up where they said they would be. Even those that did, the numbers had no "tick" marks to line up perfectly. As Broz pointed out, nightforce has a little "tick" line that lines up with their indicator at half power. Yet I would be very surprised if those are dead on either. The one we tested wasn't.
I have the scope already but havent tested it, i just took it out and saw an eagle WWAYY out there. I checked to see if i could quarter it, i could at 24x, then went on google earth and found the approx range, 3975 yards and i could quarter the eagle without much trouble. There is also a rock that is 1/4 moa high and 1/2 moa wide at 4,000 even and i could quarter it. The reticle i have is .06" at 100 yards.


Riley
__________________

I'm 15
"Firearms are second only to the Constitution in importance; they are the peoples' liberty's teeth."
~George Washington

"The only advantage a light rifle has is weight, all other advantages go to the heavy rifle."
~ JE CUSTOM

"Dope that scope and tickle that giggle switch"

~Doublezranch

Biggest fail of 2014 so far... http://www.longrangehunting.com/foru...ea-ftf-128972/
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  #75  
Old 03-05-2013, 06:52 PM
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Join Date: Mar 2012
Location: ND
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Re: First Focal Plane Vs. Second Focal Plane

Quote:
Originally Posted by phorwath View Post
Yup. It's a lot simpler for a manufacturer to put a mark on a magnification ring than to calibrate it to ensure the mark is at the exactly correct location. Same with turret adjustment values. They ought to be tested before they're accepted as correctly advertised.
And i do do that, i got the scope for christmas and i havent had a chance to test it yet.
__________________

I'm 15
"Firearms are second only to the Constitution in importance; they are the peoples' liberty's teeth."
~George Washington

"The only advantage a light rifle has is weight, all other advantages go to the heavy rifle."
~ JE CUSTOM

"Dope that scope and tickle that giggle switch"

~Doublezranch

Biggest fail of 2014 so far... http://www.longrangehunting.com/foru...ea-ftf-128972/
Reply With Quote
  #76  
Old 03-05-2013, 07:08 PM
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Join Date: Feb 2008
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Re: First Focal Plane Vs. Second Focal Plane

Quote:
Originally Posted by orkan View Post
Aaaah. I'm tracking now. I thought we were talking specifically about long range hunting, not just launching rounds at rocks for fun. I'm tracking, and agree, with that kit you would do just as you said.

However, with my Premier FFP, I'd simply back down the magnification a bit, and use my reticle for the hold. I have 65 mils (227 MOA) of holds available at 5x. An additional 28 mils available in my turret, for a total of 93 mils (325 MOA). Forgive the poor picture quality, but in the image below, you can see the hash marks every 5 mils along the entire vertical stadia, as well as windage stadia. If I dial .5 mils left, or right, I can use the tip of that stadia for a precise aim point.

Other FFP reticles have similar functionality.

Why would you need to back the magnification down on a ffp scope to acheive this????
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  #77  
Old 03-05-2013, 07:12 PM
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Join Date: Jun 2010
Location: Huron, SD
Posts: 306
Re: First Focal Plane Vs. Second Focal Plane

Quote:
Originally Posted by Franklin View Post
Why would you need to back the magnification down on a ffp scope to acheive this????
Because at 25x it looks like the image below. Not as much FOV, and not as much reticle seen.

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