Rifle Scopes UKD range finding.

[ashland]

I'm interested in ranging using my scope. I have a NF 3.5 X 15 with a NPR1 reticle. I have a good range and have verified my KD targets. My targets are 12" round plates and I'm using the formula: size of target x 95.5 divided by MOA. However when I try to use my scope, my distances are WAY off. I did adjust the 95.5 number down to 90 and was getting more accurate range estimations. Has anyone experienced this or offer some advice on getting more accurate ranges?

Thank you.

 

[EventHorizon]

Re: UKD range finding.

you're placing the division in the wrong sequence.

divide the height of the target in inches BY the number of MOA in your scope and THEN multiply that derived amount by 95.5

 

[BobinNC]

Re: UKD range finding.

Ashland,

Please define WAY off?

For example: 12" target that you range @ 2.85 MOA. The target is actually @ 400 yds exactly.

Using the formula you get 12" x 95.5 = 1146/2.85moa= 402 yds.
Your only 2 yds off.

Let's say you cannot measure that fine with your reticle, and you read it as around 2.75 MOA. Using the formula you will yield 416 yds. Now your 16 yds off

Maybe the best you can do is read it @ 2.50 MOA. Now using the formula you get 458 yds. Now your 58 yds off.

If you adjust the number down to 90; 12x90=1080/2.50moa= 432 yds. Now your only 32 yds off.

It really has nothing to do with the formula, and everything to do with how well you read your reticle.......The finer the better.

Bob

 

[Lindy]

Re: UKD range finding.

Here is the probable source of your problem, based upon the following assumptions:

(1) that scope has a reticle in the second focal plane. That means the reticle is accurate for rangefinding on one setting.

(2) that setting is the highest power.

If those assumptions are correct, what is probably the case is that the scope cannot be adjusted to a power high enough that the reticle is accurate for range finding.

I have seen that problems on a number of scopes - including those from Nightforce.

You can check for that problem using techniquest described in this reference: Optically Checking Rifle Scopes

If that turns out to be the problem, calibrate the scope at the highest power it will turn to. Then figure out how much error you have, and calculate a correction factor.

 

[Guest]

Re: UKD range finding.

The first thing to do is verify that the reticle is subtending what it's supposed to at distance, on either a Barber pole, or yard stick at 100yds.

Bright Colors, lighting difference's, and target angle's will also effect your ability to reticle range correctly. R/R'ing is a task in and of it's self. If you do it long enough you'll find which colors effect you the most, how to read the lighting, an comp for the angles.

 

[cooper623]

Re: UKD range finding.

If you are in Mils, you use the following for formula

(height of target in inchesx25.4)/Mil Reading

For MOA you use....

(height of target in inches x 27.7)/ MOA Reading

....there are different ways to do it but i find this to be the best. Also in terms of how accurate you need to be, you need to estimate to the nearest .1 but as long as you get it close enough to where you round to the correct 50 yard increment for your dope youre good. A great place to practice is shooterready.com they have great software but offer a very good free sample that allows you to more or less replicate your set up.

 

[Lowlight]

Re: UKD range finding.

The formulas above are completely wrong.

SOT in inches x 27.77 / Sot in mils= range in yards

Sot in inches x 25.4 / Sot in mils = range in meters

Sot in inches x 95.5 / Sot in moa = range in yards

 

[Guest]

Re: UKD range finding.

To add, if your reticle is in IPHY,

Target in inchs / reticle subtention X 100 = yardage

 

[BobinNC]

Re: UKD range finding.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: cooper623</div><div class="ubbcode-body">If you are in Mils, you use the following for formula

(height of target in inchesx25.4)/Mil Reading

For MOA you use....

(height of target in inches x 27.7)/ MOA Reading

....there are different ways to do it but i find this to be the best. Also in terms of how accurate you need to be, you need to estimate to the nearest .1 but as long as you get it close enough to where you round to the correct 50 yard increment for your dope youre good. A great place to practice is shooterready.com they have great software but offer a very good free sample that allows you to more or less replicate your set up. </div></div>

Cooper,

If that the way you calculate it's a wonder you hit anything.

This is the correct formula for MILS in Yds.

Height of Target (inches) x 27.78 = Distance (yards)
mils

The is the formula for MILS in Meters:

Height of Target (inches) x 25.4 = Distance (meters)
mils

This is the formula for MOA in YDS.:

Height of Target (inches) x 95.5 = Distance (yards)
moa

Now lets Prove the formulas:

Target size 12" actual range 400 yds:

Using MILS formula:

12" x 27.78 = 333.36/.83 Mils= 401.6 Yds

Using the MOA Formula:

12" x 95.5 = 1146/2.85 MOA = 402 yds.

Bob

 

[ashland]

Re: UKD range finding.

Thanks everyone for posting. I'm at work and don't have my data book with me right now. I'm usually off by 50 to 70 yds and that's a big difference to me. I do have this scope turned up to the highest power and it is a SFP scope. Frank, that's why I had trouble on your UKD targets at the PR3A class. I overheard a shooter with what sounded like the correct range and used his info. I cheated. Sorry.

Lindy, I will check that information you listed. I'm using the correct formula of in. x 95.5 and what I think is the right MOA call.

I'll go over this information again and give it a try.

Thank you.

 

[sscoyote]

Re: UKD range finding.

I would definitely measure the reticle subtension at the optic's highest power. Another way to find out what your subtension is is to go out and reticle-range 10 targets of known dimension and reverse mil the true subtension using an average of all your readings.

 

[ashland]

Re: UKD range finding.

Ok, I'll give that a try. Guess if I wanted to use the scope for range finding, I should have bought an FFP.

Thanks everyone.

 

[Graham]

Re: UKD range finding.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ashland</div><div class="ubbcode-body">Guess if I wanted to use the scope for range finding, I should have bought an FFP.</div></div>Nope. Just use it like a fixed 15x for ranging, and use the correct formula.

 

[427Cobra]

Re: UKD range finding.

A Mildot Master will work just fine a NF with a NPR1 reticle