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Rifle Scopes Nightforce rangng with SFP at lower power
- Thread starter CST
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Re: Nightforce rangng with SFP at lower power
7.5
Unfortunately this isn't marked, at least on mine.
7.5
Unfortunately this isn't marked, at least on mine.
Re: Nightforce rangng with SFP at lower power
You need to calibrate your reticle to find out for sure. Even NF's have some variance in where exactly the ranging point is.
Cheers,
Doc
You need to calibrate your reticle to find out for sure. Even NF's have some variance in where exactly the ranging point is.
Cheers,
Doc
Re: Nightforce rangng with SFP at lower power
Right, at somewhere around 7.5 mils, each half-mil hash mark is a mil, and each mil hash mark is two mils.
Just check it on paper to find out where it works out and mark it. On my 6.5-20 Leupold it works out to the 12x marking, not 10.
Right, at somewhere around 7.5 mils, each half-mil hash mark is a mil, and each mil hash mark is two mils.
Just check it on paper to find out where it works out and mark it. On my 6.5-20 Leupold it works out to the 12x marking, not 10.
Re: Nightforce rangng with SFP at lower power
Of note:
At a school earlier this month, Doc ran us through an exercise to check that the mil dots/lines in our scopes were correct at precisely 100 yards. Pretty critical for a bunch of LEO shooters.
My Mk IV was one of only about half (!?!) the scopes that passed the test and were really accurate for ranging. The rest (all high-end optics) were not quite correct from the factory. As I recall, 11 out of 24 were not right.
Issues showed up especially in the elevation marks below the windage line (bottom half of the scope.) The lines were off based on a test pattern set up at 100.
If you are trying to mil at longer ranges (+400), the percentages will add up and really mess up your range estimations.
For those who may depend on milling (or want it as a reliable backup to a LRF) this test is pretty critical. It also requires nothing more than a big piece of paper and a ruler.
If he is willing, Doc can explain the process better than I can. The tests he ran us through taught us a lot about our optics.
Cheers,
Sirhr
Of note:
At a school earlier this month, Doc ran us through an exercise to check that the mil dots/lines in our scopes were correct at precisely 100 yards. Pretty critical for a bunch of LEO shooters.
My Mk IV was one of only about half (!?!) the scopes that passed the test and were really accurate for ranging. The rest (all high-end optics) were not quite correct from the factory. As I recall, 11 out of 24 were not right.
Issues showed up especially in the elevation marks below the windage line (bottom half of the scope.) The lines were off based on a test pattern set up at 100.
If you are trying to mil at longer ranges (+400), the percentages will add up and really mess up your range estimations.
For those who may depend on milling (or want it as a reliable backup to a LRF) this test is pretty critical. It also requires nothing more than a big piece of paper and a ruler.
If he is willing, Doc can explain the process better than I can. The tests he ran us through taught us a lot about our optics.
Cheers,
Sirhr
Re: Nightforce rangng with SFP at lower power
Guther et al:
If Doc can explain or post pictures, so much the better. I will try and give a basic runthrough of the process, but apologize in advance for any errors I put into this, as I was just a student here. So hopefully, Doc can correct my errors.
But the basic version is that on a large piece of paper or graph paper, you draw a theoretically perfect grid pattern of your Mil Lines with a Sharpie or similar. Space them vertically and horizontally at the correct center-to-center distance for your milling scope. It could be 3.375. Could be 3.6 Use the correct number for your scope. That number should be in your scope manual. Keep that page in your databook, BTW.
Then, position your scope so that the erector lens (in the middle of the scope, where the knobs are roughly) is right on a 100 yard line. Measure distance to your target with a tape, not another rangefinder. Sandbag the rifle or make it stable on a bench. Level with target.
You may need to adjust (back off) the power slightly from the stops so that the lines (or at least most of them) come into perfect alignment. The lines on your reticle must be superimposed with the grid on the paper. Adjusting the power ring is also important, because it will tell you whether you should be milling at Full power (ie. the stops) or if the power ring might be slightly off the reticle. If this is the case, your scope may not be giving you the exact data for accurate long range estimation.
On my scope, I did have to back off a fraction on power to get the lines to all match up. Not much, but some. I marked this on the ring, BTW, so I know right where my power ring needs to be to get accurate milling measurements.
At this point, the lines on both windage and elevation stadia lines should mate up perfectly. Every line should be superimposed on its corresponding line on your target.
What Doc found was that almost half of scopes had mil lines that were engraved or etched "off" on the reticles by a slight amount, apparently cascading so that the errors accumulated at the periphery.
Again, assuming he is willing, I'll let him explain the process as he knows the test. I was just a willing student. But it was very eye-opening for a lot of our shooters.
And though my scope "passed" the test for its reticle, it did not mill perfectly at full power and I needed to make an mark to ensure I set it right to get correct power for milling.
Hope this helps and, again, apologize in advance for any errors. But hopefully this will give you a start until someone better can explain.
Cheers,
Sirhr
(PS) I own and prefer a quality laser rangefinder. But if it has wheels or batteries... sooner or later it will give you trouble. Ranging is a good skill to know inside and out.
Guther et al:
If Doc can explain or post pictures, so much the better. I will try and give a basic runthrough of the process, but apologize in advance for any errors I put into this, as I was just a student here. So hopefully, Doc can correct my errors.
But the basic version is that on a large piece of paper or graph paper, you draw a theoretically perfect grid pattern of your Mil Lines with a Sharpie or similar. Space them vertically and horizontally at the correct center-to-center distance for your milling scope. It could be 3.375. Could be 3.6 Use the correct number for your scope. That number should be in your scope manual. Keep that page in your databook, BTW.
Then, position your scope so that the erector lens (in the middle of the scope, where the knobs are roughly) is right on a 100 yard line. Measure distance to your target with a tape, not another rangefinder. Sandbag the rifle or make it stable on a bench. Level with target.
You may need to adjust (back off) the power slightly from the stops so that the lines (or at least most of them) come into perfect alignment. The lines on your reticle must be superimposed with the grid on the paper. Adjusting the power ring is also important, because it will tell you whether you should be milling at Full power (ie. the stops) or if the power ring might be slightly off the reticle. If this is the case, your scope may not be giving you the exact data for accurate long range estimation.
On my scope, I did have to back off a fraction on power to get the lines to all match up. Not much, but some. I marked this on the ring, BTW, so I know right where my power ring needs to be to get accurate milling measurements.
At this point, the lines on both windage and elevation stadia lines should mate up perfectly. Every line should be superimposed on its corresponding line on your target.
What Doc found was that almost half of scopes had mil lines that were engraved or etched "off" on the reticles by a slight amount, apparently cascading so that the errors accumulated at the periphery.
Again, assuming he is willing, I'll let him explain the process as he knows the test. I was just a willing student. But it was very eye-opening for a lot of our shooters.
And though my scope "passed" the test for its reticle, it did not mill perfectly at full power and I needed to make an mark to ensure I set it right to get correct power for milling.
Hope this helps and, again, apologize in advance for any errors. But hopefully this will give you a start until someone better can explain.
Cheers,
Sirhr
(PS) I own and prefer a quality laser rangefinder. But if it has wheels or batteries... sooner or later it will give you trouble. Ranging is a good skill to know inside and out.
Re: Nightforce rangng with SFP at lower power
Hi all,
The method for calibrating your reticle is a rather simple event that doesn't require shooting. It does take some effort to ACCURATELY lay out the grid and position the rifle and grid at exactly the correct location.
The grid is simply a series of lines or points that will show what your reticle "should" subtend. I have access to graph paper on a roll that is divided into 1' and 1/10" squares which helps. Basically you need to lay out lines (for a mil dot reticle) that are EXACTLY 3.6" apart in an vertical and horizontal axis.
Put the grid at EXACTLY 100 yards. A laser is not sufficiently accurate for this measurement you need to do it with a tape. Lufkin makes a 300' tape for about $20.00 at Home Depot or Lowes.
For a 2nd Focal Plane scope sit the POWER RING on the 100 yard mark. For a 1st Focal Plane scope the turrets need to be on the mark.
From there get down behind the rifle and turn the power ring until the the reticle matches the lines on the paper. This is where you need to be very precise because small errors here will stack at distance. If you dial and hit the hard stop and the grid is even slightly smaller than the reticle your scope will not adjust (subtend) correctly. If your grid is larger you will be able to back off the power to match them.
To determine your 1/2 power dial down the power until one mil dot in your reticle lines up with 2 marks on the paper.
Common errors found
- Scope cannot adjust enough to correctly subtend
- Scope adjusts too much and the correct setting is not on the hard stop
- Reticle subtends correctly in the middle but not at the ends
- Mil-dots are not evenly spaced
All of the above were noted at the class Sirhr attended.
Hope that makes sense.
Cheers,
Doc
Hi all,
The method for calibrating your reticle is a rather simple event that doesn't require shooting. It does take some effort to ACCURATELY lay out the grid and position the rifle and grid at exactly the correct location.
The grid is simply a series of lines or points that will show what your reticle "should" subtend. I have access to graph paper on a roll that is divided into 1' and 1/10" squares which helps. Basically you need to lay out lines (for a mil dot reticle) that are EXACTLY 3.6" apart in an vertical and horizontal axis.
Put the grid at EXACTLY 100 yards. A laser is not sufficiently accurate for this measurement you need to do it with a tape. Lufkin makes a 300' tape for about $20.00 at Home Depot or Lowes.
For a 2nd Focal Plane scope sit the POWER RING on the 100 yard mark. For a 1st Focal Plane scope the turrets need to be on the mark.
From there get down behind the rifle and turn the power ring until the the reticle matches the lines on the paper. This is where you need to be very precise because small errors here will stack at distance. If you dial and hit the hard stop and the grid is even slightly smaller than the reticle your scope will not adjust (subtend) correctly. If your grid is larger you will be able to back off the power to match them.
To determine your 1/2 power dial down the power until one mil dot in your reticle lines up with 2 marks on the paper.
Common errors found
- Scope cannot adjust enough to correctly subtend
- Scope adjusts too much and the correct setting is not on the hard stop
- Reticle subtends correctly in the middle but not at the ends
- Mil-dots are not evenly spaced
All of the above were noted at the class Sirhr attended.
Hope that makes sense.
Cheers,
Doc
Re: Nightforce rangng with SFP at lower power
question for doc will the same type of graph work for a nightforce npr-1 retice that uses moa to range the reticle is 1 moa vertical/distaqnce and 2 moa horizontal/windage at full power.
question for doc will the same type of graph work for a nightforce npr-1 retice that uses moa to range the reticle is 1 moa vertical/distaqnce and 2 moa horizontal/windage at full power.
Re: Nightforce rangng with SFP at lower power
Thanks alot for your time and the info. I am going to the range on Sunday with my graph paper to re-check mine. My scope is a Nightforce 5.5 X 22 mil dot. Must make sure it is right!
Guther
Thanks alot for your time and the info. I am going to the range on Sunday with my graph paper to re-check mine. My scope is a Nightforce 5.5 X 22 mil dot. Must make sure it is right!
Guther
Re: Nightforce rangng with SFP at lower power
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: doc76251</div><div class="ubbcode-body">To determine your 1/2 power dial down the power until one mil dot in your reticle lines up with 2 marks on the paper.</div></div>
I'm confused, if you dial down wouldn't it be half? The object is getting smaller, not larger. So 2 mildots in your scope would line up with 1 mark on the paper? 1 would be 1/2 on paper, but there are no half markings, so that's why i went with 2 mils in your scope.
Also i'm not sure i follow the "doubling". If something is 3 mils in your scope at 15x, how is it 6 mils at 7.5x? Wouldn't it be 1.5 mils at 7.5x? If you double the magnification to 30x then it would 6 mils wouldn't it? Again isn't the object getting smaller covering less space when zooming out?
A 12" object at 15x measuring 3 mils
333.33/3 = 111 yds
At 7.5x it'll measure 1.5 mils
333.33/1.5 = 222.22/2(half power) = 111 yds
At 30x, 6 mils
333.33/6 = 55.55*2(2x power) = 111 yds
Or am i completely misunderstanding this mildot thing??
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: doc76251</div><div class="ubbcode-body">To determine your 1/2 power dial down the power until one mil dot in your reticle lines up with 2 marks on the paper.</div></div>
I'm confused, if you dial down wouldn't it be half? The object is getting smaller, not larger. So 2 mildots in your scope would line up with 1 mark on the paper? 1 would be 1/2 on paper, but there are no half markings, so that's why i went with 2 mils in your scope.
Also i'm not sure i follow the "doubling". If something is 3 mils in your scope at 15x, how is it 6 mils at 7.5x? Wouldn't it be 1.5 mils at 7.5x? If you double the magnification to 30x then it would 6 mils wouldn't it? Again isn't the object getting smaller covering less space when zooming out?
A 12" object at 15x measuring 3 mils
333.33/3 = 111 yds
At 7.5x it'll measure 1.5 mils
333.33/1.5 = 222.22/2(half power) = 111 yds
At 30x, 6 mils
333.33/6 = 55.55*2(2x power) = 111 yds
Or am i completely misunderstanding this mildot thing??
Re: Nightforce rangng with SFP at lower power
You have it backwards. Doc is correct.
At half power the space between the reticle-dots covers twice the distance on the target.
You have it backwards. Doc is correct.
At half power the space between the reticle-dots covers twice the distance on the target.
Re: Nightforce rangng with SFP at lower power
The observed object is getting smaller but the fixed reticle (mil or whatever in 2FP) is covering more of the object. Therefore, the correct subtention is lost.
To put it on observed terms; the milrad expects a certain "height" at range (or length at target) to actually be a milrad. The reticle is scaled to function at A magniifcation (ex: 15x).
With the 2FP, the reticle is fixed so if you reduce magnification 1/2 the "mildots" now cover twice the span in the optical image and need to be corrected by ratio to compensate.
This practice assumes that the optic in question has a magnification factor correct with the markings or the user's expectation.
The observed object is getting smaller but the fixed reticle (mil or whatever in 2FP) is covering more of the object. Therefore, the correct subtention is lost.
To put it on observed terms; the milrad expects a certain "height" at range (or length at target) to actually be a milrad. The reticle is scaled to function at A magniifcation (ex: 15x).
With the 2FP, the reticle is fixed so if you reduce magnification 1/2 the "mildots" now cover twice the span in the optical image and need to be corrected by ratio to compensate.
This practice assumes that the optic in question has a magnification factor correct with the markings or the user's expectation.
Re: Nightforce rangng with SFP at lower power
To do MOA reticles the measurements are more precise and harder to duplicate on paper. I was doing it with dividers to get it exactly correct. My son was watching me barely control my tongue while trying to get it to work out one night. He showed me a neat trick to get the lines to work out.
Measure out the length you need (10.47" = 10 MOA)
Then draw or fix a line that is perpendicular so that you can use a yard stick to measure out 20" from the end of the original line to somewhere on the perpendicular line.
You will have a triangle.
Measure along the yardstick and mark every 2".
From there if you can accurately measure each mark to the perpendicular line you can transpose the length to the original line.
There are probably better ways to explain it and drafting tools or a carpenters square is REALLY handy but that is the easiest way I have found to do it.
Yote - Boom and Raf explained it well. Essentially the reticle remains the same while the "field of view" gets larger. An object in the FOV will get smaller this is why you look for your 1/2 power setting. Your previously calculated holds for movers, wind etc. still work you just need to "halve" them.
Cheers,
Doc
To do MOA reticles the measurements are more precise and harder to duplicate on paper. I was doing it with dividers to get it exactly correct. My son was watching me barely control my tongue while trying to get it to work out one night. He showed me a neat trick to get the lines to work out.
Measure out the length you need (10.47" = 10 MOA)
Then draw or fix a line that is perpendicular so that you can use a yard stick to measure out 20" from the end of the original line to somewhere on the perpendicular line.
You will have a triangle.
Measure along the yardstick and mark every 2".
From there if you can accurately measure each mark to the perpendicular line you can transpose the length to the original line.
There are probably better ways to explain it and drafting tools or a carpenters square is REALLY handy but that is the easiest way I have found to do it.
Yote - Boom and Raf explained it well. Essentially the reticle remains the same while the "field of view" gets larger. An object in the FOV will get smaller this is why you look for your 1/2 power setting. Your previously calculated holds for movers, wind etc. still work you just need to "halve" them.
Cheers,
Doc
Re: Nightforce rangng with SFP at lower power
The easiest way I have found to accurately dial to the half power point on a mil-reticle scope is to place two orange 1-inch Shoot'N'C dots on an 8 foot length of 2X2 piece of wood so that the <span style="font-style: italic">center</span> of the dots are exactly 72 inches apart.
Then, using a tape measure as Doc said, place that exactly 100 yards away.
Dial the scope down until 10 mils marked on the scope are exactly on the center of the dots. Mark the dial at that point.
My method for doing that with a MOA reticle is not to own a scope with a MOA reticle.
However, what I would do is to pick some large chunk of the MOA reticle. A round equivalent of 10 mils would be 40 MOA. Two dots 40 MOA apart <span style="font-style: italic">at half power</span> would be 83.76 inches apart - which is close enough to 83.75 that the error wouldn't matter.
The point is to use widely spaced points to reduce measurement error.
To use the half-power points, divide your holds by 2. So, if at full power, I'd be holding 1 mil, at half power I'd hold 0.5 mil, because the size of the reticle stays the same, but now it covers twice as much distance.
The easiest way I have found to accurately dial to the half power point on a mil-reticle scope is to place two orange 1-inch Shoot'N'C dots on an 8 foot length of 2X2 piece of wood so that the <span style="font-style: italic">center</span> of the dots are exactly 72 inches apart.
Then, using a tape measure as Doc said, place that exactly 100 yards away.
Dial the scope down until 10 mils marked on the scope are exactly on the center of the dots. Mark the dial at that point.
My method for doing that with a MOA reticle is not to own a scope with a MOA reticle.
However, what I would do is to pick some large chunk of the MOA reticle. A round equivalent of 10 mils would be 40 MOA. Two dots 40 MOA apart <span style="font-style: italic">at half power</span> would be 83.76 inches apart - which is close enough to 83.75 that the error wouldn't matter.
The point is to use widely spaced points to reduce measurement error.
To use the half-power points, divide your holds by 2. So, if at full power, I'd be holding 1 mil, at half power I'd hold 0.5 mil, because the size of the reticle stays the same, but now it covers twice as much distance.
Re: Nightforce rangng with SFP at lower power
I got a response from Nightforce....tell me what you think..
"Your Nightforce scope can be used at any power, when you use this simple formula.
Calibration power,(15X) divided by operating power.
Example:
You want to shoot at 7 power and would like to know the Mil values on your reticle.
15X/7X =2.14
This would mean that at 7 power, you would have 2.14 mils per line. Or 1.7 mils per small dash."
------ so according to this formula you can mill anything at any power if you can accurately calculate the relationship.
so 7.5x is correct to be exactly half..so if you mill something at 7.5x you simply double it and put it thru your range equation or mildot master
I got a response from Nightforce....tell me what you think..
"Your Nightforce scope can be used at any power, when you use this simple formula.
Calibration power,(15X) divided by operating power.
Example:
You want to shoot at 7 power and would like to know the Mil values on your reticle.
15X/7X =2.14
This would mean that at 7 power, you would have 2.14 mils per line. Or 1.7 mils per small dash."
------ so according to this formula you can mill anything at any power if you can accurately calculate the relationship.
so 7.5x is correct to be exactly half..so if you mill something at 7.5x you simply double it and put it thru your range equation or mildot master
Re: Nightforce rangng with SFP at lower power
However, that depends on your magnification markings being calibrated exactly, e.g. is 7X really 7X or is it 7.2X? At 400 yards, that means 11 yards of error. Not much, but there are enough variables already that you don't want to add any error. Also, you have one extra calculation to perform. Being able to range at any magnification* is one advantage of an FFP scope.
*Most reticle subtensions are too small to see at low magnification, such as 3X, but then you are usually close enough for a point blank shot.
However, that depends on your magnification markings being calibrated exactly, e.g. is 7X really 7X or is it 7.2X? At 400 yards, that means 11 yards of error. Not much, but there are enough variables already that you don't want to add any error. Also, you have one extra calculation to perform. Being able to range at any magnification* is one advantage of an FFP scope.
*Most reticle subtensions are too small to see at low magnification, such as 3X, but then you are usually close enough for a point blank shot.
Re: Nightforce rangng with SFP at lower power
If your mil-dots are accurate at 15x at 100 yards, then mark dots 3.6 inches or so apart at 100 yards. Then line up the dots at 50 yards and you'll be at 7.5 magnification, then you can mark it on your scope. This would work best with a laser range finder to make sure the distances are exactly right.
Good luck!
If your mil-dots are accurate at 15x at 100 yards, then mark dots 3.6 inches or so apart at 100 yards. Then line up the dots at 50 yards and you'll be at 7.5 magnification, then you can mark it on your scope. This would work best with a laser range finder to make sure the distances are exactly right.
Good luck!
Re: Nightforce rangng with SFP at lower power
Laser rangefinders are not accurate enough if you want accuracy. A tape measure is much better.
And while what you posted will work, I posted an easier method above, which works at 100 yards.
Also, it doesn't matter if the reticle is accurate at 15X. If you calibrate it as I outlined above, it's accurate at 7.5 power, were you will mark it, whether or not it's accurate at 15 X.
Also see Optically Checking Rifle Scopes.
Laser rangefinders are not accurate enough if you want accuracy. A tape measure is much better.
And while what you posted will work, I posted an easier method above, which works at 100 yards.
Also, it doesn't matter if the reticle is accurate at 15X. If you calibrate it as I outlined above, it's accurate at 7.5 power, were you will mark it, whether or not it's accurate at 15 X.
Also see Optically Checking Rifle Scopes.
Re: Nightforce rangng with SFP at lower power
If you don't want to draw you own grid lines, we have already done it and have free printable targets for reticle verification for MIL and MOA reticles at yard and meter ranges. They print on 8.5"x11" paper. These come with our Data Book CDROM, but I can email to anyone who wants them. All the best. Mark
If you don't want to draw you own grid lines, we have already done it and have free printable targets for reticle verification for MIL and MOA reticles at yard and meter ranges. They print on 8.5"x11" paper. These come with our Data Book CDROM, but I can email to anyone who wants them. All the best. Mark
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