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NP-R2 Range Estimation

 
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  #1  
Old 02-16-2003, 06:50 PM
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NP-R2 Range Estimation

Regarding range estimation with the NP-R2 reticle, I read in previous posts that the accuracy potential is greater than that with the mil-dot reticle. I am currently using a NF NXS with mil-dot reticle. When I mil my intended target sometimes my readings are in smaller fractions than 10ths...e.g., instead of reading .6mil, or .7mil, I may get a more precise reading of say .65, or .75

In an example using a 20" target (top to bottom) If I get a mil reading of .65, my distance equals 854.46yds. In comparison, using the 2 moa tick marks, I would need a reading of approx 2.35moa to get the same answer. Question, Is it possible to get this type of fine reading?
Obviously in this example, the users familiarity with this type of reticle is going to play a major role, since visualizing the differentiation is a difficult skill. My question is, how are you visually breaking down the 2&5moa tick marks on the NP-R2, to get the most precise reading?

Thanks,
Luke[LIST]
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Old 02-17-2003, 06:19 AM
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Re: NP-R2 Range Estimation

Hey Luke,

The best resolution I think the R2 reticle provides is .2 moa, or 1 tenth of a line. This is pretty easy to break down like this. The 12-42x56 has the advantage of twice this resolution if set on 42 power and would be .1 moa. On 42x the lines are equal to 1 moa now not 2 moa.

The best use of the 5.5-22x NF is with bigger targets in the 36-40" range. Here you can stay under about 30-35 yards per .2 moa increment. If the target is say 20" like your example, it is much more difficult to range to within this 30-35 yard range.

The larger the targets size you're dividing into the more closely each range increment will be to each other. Range increments get farther apart the longer the range as well. This is the exact opposite of what we want as a LR hunter too.

After about 800 yards the the distance between each .2 moa increment on a 40" target is stretching to over 30 yards so it does have it's limitations beyond this. On a 20 inch target the limit might be around 600 yards. If you are using a 42x NF this of course would be a different story because of it's greater resolution.

The method I use is to measure the animal and count the number of lines high, say 2.7 lines. I divide half the targets size by this number and move the decimal two places to the right. Example; 40" chest on this moose measures 2.7 lines tall. Half the chest size 20"/2.7 lines = 7.40 or 740 yards.

Examples of other increments with a 40" target would be;

3.0 = 666 yards
2.9 = 689
2.8 = 714
2.7 = 740
2.6 = 769
2.5 = 800
2.4 = 833
2.3 = 869
2.2 = 909
2.1 = 952
2.0 = 1000

If you do the same thing using a 20" target (dividing by half that though) you'll see a much larger distance between the one tenth increments though.

Examples of other increments with a 20" target would be;

2.0 = 500 yards
1.9 = 526
1.8 = 555
1.7 = 588
1.6 = 625
1.5 = 666
1.4 = 714
1.3 = 769
1.2 = 833
1.1 = 909
1.0 = 1000

In the same range, you can see the smaller target doesn't work as well and range increments are far too large to be usefull past about 600yds. If you factor in about a 10% error for judging the targets size, which could be at an angle or obstructed some, you'd probably be safe to 800 yards or so if you're shooting a high BC bullet at pretty high velocity on a 36-40" rangeable object.

How are you judging size using the Mil-Dot to within .05 mil? Are you able to do this in increments of .05 mil?

Given the fact that .05 mil is about .2 moa, that would be comparable to the NF 5.5-22 or 8-32, but again the 12-42 would give double this resolution.

I don't see how the mil-dot can give increments of .05 mil (or .2 moa) but I'm open to ideas. It does have an outer ring that is .2 moa thick and a center dot that is .1 moa in size, I guess you could use these sizes in multiples to an extent, but as far as offering .05 mil or .2 moa increments that isn't there. This is one difficult thing to deal with, for me anyway.

Here's something that might help with the mil-dot.

Mil-Dot specs;

1.0 mil = 3.6 moa (dots between centers)
.88 mil = 3.2 moa (center crosshair to edge of first dot)
.75 mil = 2.7 moa (between edges of dots)
.50 mil = 1.8 moa (half way between dot centers)
.25 mil = 0.9 moa (size of dot)
.13 mil = 0.5 moa (half size of dot)
.06 mil = 0.2 moa (thickness of dots outer ring) Nightforce Mil-Dot
.03 mil = 0.1 moa (center dot size) Nightforce Mil-Dot


[ 02-17-2003: Message edited by: Brent ]
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  #3  
Old 02-17-2003, 04:39 PM
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Re: NP-R2 Range Estimation

Brent,
Thanks for the reply. Using an example to answer your question on mil estimation using .05 increments, I am basically visualizing what appears to be "not quit" a true .7 or .6, it then becomes .65

I am not saying this is easy, however, very much possible.

I can walk that out in the .05 increments as needed...e.g., 1.5,1.55,1.6,1.65,...etc

All of the guys that use this reticle that I shoot with, maintain these types of readings to get the most accurate capability out of the estimation.

As you said, out at 1000yds it becomes very difficult to get any reading period. At the greater distances, with the smaller targets, I am happy to break it down into the 10th's...e.g., .6, .7, .8,etc. I realize the limitations of the mil-dot at greater ranges, and was wondering if the NP-R2 moa ranging had a leg up on it somehow.

Reading other posts about the NP-R2, there was mention of it working best as a calibrated hold over reticle if the velocity was up around 3300+fps. I am only humming along at around 3000fps (.300WM). Realizing that, the benefit I was hoping for was that I was thinking about speaking in the same moa language of the turrets. This would eliminate some extra thinking for the shooter I would think.

Thanks for your input; if you have any more info, I would appreciate it.

Luke
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Old 02-17-2003, 07:12 PM
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Re: NP-R2 Range Estimation

Hey Luke,

I'm not sure I understand how you can do this in increments still.

Walk me through it using your example if you would. My dad uses the mil-dot in several of his but I've never taken to them myself.

I can walk that out in the .05 increments as needed...e.g., 1.5,1.55,1.6,1.65,...etc

Tell me how you'd measure each of those increments with what you'd be using as a reference with each one.

The R2's bars that are 2 moa apart can be visually split in half and then again 5 equal times for real .2 moa increments. This is really pretty easy to get that accurate. Sometimes you can even see it isn't falling on a "visualized" .2 moa line and falls in between, so it can be more accurate than this even, I suppose. This is especially true if the target has really defined edges.

At this point I still see the R2 as being quicker to get a measurement, more accurate and quicker to figure the range in your head with the numbers you get.

A custom modified R2 I'd like to see would add bars placed at 1 moa increments being 1 moa wide instead of 2, with bars placed at .5 moa increments being .5 moa wide and this one being a finer line as well, .1 moa width would be good.
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Old 02-19-2003, 05:11 PM
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Re: NP-R2 Range Estimation

Brent,
Thanks for explaining your NP-R2 in detail. I also appreciate the open mind. I hope this explains it well for you.
Here is a basic idea of how I use my scope. As I mentioned, I am using a NXS, mine is in 3.5x15x50 w/mil dot reticle. As you’re aware, the dot represents .25mil, with half dot representing .125
I too find the divisions difficult to work with, even though I have used this type of reticle for some time. Based on the .25 mil dot, the space between the inside edges of the dots represent .75
Most guys will then visually divide the .75 into 6 even increments of .125 -The .75 added to each half dot of .125 equals the total 1.0 mil
The problem I have, is the difficulty in quickly attaining the smaller increments as I had discussed with you previously, e.g. when you have a reading that is in the middle of a perceived division…5.5,6.5, etc. In the case of the .125 increments, the midway reading between your visual mark would give you a number like .0625 - This added to the whole of .125, gives you .1875 - This to me is not fast or easy to work with; like your Dad, making the smaller readings is not happening.

This is what I do. I totally disregard the fact that the dot is .125, and treat it like it is .1 - I then treat the .75 spacing as if it where .8 - By doing this, I divide the inside .75 spacing into 8 divisions. To get the 10th reading that I am looking for, I add the halves of each dot on each side. Center of dot to center of dot is 1.mil regardless of how I mentally chop it. Breaking down the center .75 spacing into 8, I get 8 divisions of .0937, rounding to .094 – This is very close to the .1 value.

Here is a breakdown taking the .75 space and dividing into 8ths equaling (.094) each. I add them along the way to show the progression as if you where reading your reticle. The first measurement starts from the inside edge of the dot. Take any of these numbers along the way, and add it to your half dot of .125 – If you have a full mil, you will be starting from the center of a dot to get the remaining measurement. This would be your base to start from where you know that regardless of anything that you are doing, the measurement is a full 1. mil. Your answer will be within a few hundredths.

Divided actual increments - .094 - .188 - .282 - .376 - .47 - .564 - .658 - .752
Shooters used increments - .1 .2 .3 .4 .5 .6 .7 .8
Adjusted w/+ .125 half dot - .219 .313 .407 .501 .595 .689 .783 .877
Shooters total reading - .2 .3 .4 .5 .6 .7 .8 .9

The bottom row represents the measurement from the center of the dot out to your divisions, adding along the way to show the reading.

Here is a working example: 30” target – (30” x 27.77 = constant of 833.1)

Shooters method: Mil reading 1.1 833.1 ¸ 1.1 = 757 yds
School house method: Mil reading 1.125 833.1 ¸ 1.125 = 741 yds
Difference = 18yds

Shooters method: Mil reading .9 833.1 ¸ .9 = 926yds
School house method: Mil reading .875 833.1 ¸ .875 = 952yds
Difference = 26yds

Let me know if you have any questions. I have more to tell you however, I have to get some sleep (work in 6hrs).
Luke
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Old 02-19-2003, 05:19 PM
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Re: NP-R2 Range Estimation

Brent,
The formula didn't come out readable on the post, here it is again.

Here is a working example: 30” target – (30” x 27.77 = constant of 833.1)

Shooters method: Mil reading 1.1 -- C= 833.1 / 1.1 = 757 yds
School house method: Mil reading 1.125 -- C= 833.1 / 1.125 = 741 yds
Difference = 18yds

Shooters method: Mil reading .9 -- C= 833.1 / .9 = 926yds
School house method: Mil reading .875 -- C= 833.1 / .875 = 952yds
Difference = 26yds

Luke
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Old 02-19-2003, 07:52 PM
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Re: NP-R2 Range Estimation

Now that's a workable system there, great job! [img]images/icons/wink.gif[/img]

It's new so I'm a little slow at it yet. I don't understand one thing in your 30" target example though. You indicate two different mil readings, one at 1.1, the other at .9, will you explain the why there is two different ones and how you got them. I know I'm missing your point because of this. My brain hurts, so I'll let you explain it rather than study it any longer. I'm sure you'll point out in a sentance, what will take me an hour to figure out. [img]images/icons/grin.gif[/img] I do fairly well with math, but mil-dot math is something I still have to try hard to follow, thanks for the detailed explanation, everything else makes perfect sense. [img]images/icons/smile.gif[/img]

Breaking it down into moa instead of mil's would be even simpler on the brain if it could be done as accuratly.
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