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3-9x40 IR Range-Finding Graph Reticle

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/14/2010 at 16:34
keo View Drop Down
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I recently purchased a low-cost bargain scope, sold under the name of Warsensor, marketed to the paintball crowd. This is just a rebadged scope that many companies sell, and, is actually quite nice (within reason). Other companies sell the exact same one for upwards of $100, I got it for $10, brand-new. It has an 11 light-levels illuminated reticle, named by Barska as the "IR Range-Finding Graph Reticle". Other companies like Tasco, NcStar, and others just call it a "Rangfinder Reticle". They all use the same one. If you want to seek out their original Chinese supplier just do a search for "3-9x40E" (I'm including all these various names it is badged under so anyone who has one will get a hit on this post from a search engine one day to help end their frustration, as I have had for a week looking.)

I have been searching the net for a week looking for further information on this reticle design and how the lines and marks in the reticle relate to real-world measurements.

Well, I finally gave up looking and decided to do my own measurements yesterday. What follows are graphics with some simple measurements (estimated as well as I could) taken at 50-yard and 100-yard distances. Measured against a yardstick at various magnifications, to try to make sense of this reticle.

The reticle layout used in these images posted here are taken from an actual photograph of the reticle as seen through the scope I own. So if anyone wants to do further measurements of the various lines and spacings directly from these notated photos, it is accurate as the eye sees it, not an edited mock-up of what it almost looks like (which I have also found on the net and found that was useless for measurements).

If anyone would like to explain the proper magnification power to use this thing, and deduce what the lower range-finding spaces imply to yardage, it would be appreciated. Are they supposed to denote a meter width at 100, 130, 160, 200, etc. meters? Or what?

Here's with the scope set at 9x at 100 yards:


Here's 9x at 50 yards:


Here's 6x at 100 yards:


Here's 7x at 50 yards:



I'm guessing, from the looks of these measurements, that this reticle was designed to be used at 10x at 100 yards. Or for metric measurements?

This reticle appears in many many many low-cost scopes lately. Perhaps someone can help to figure what magnification and yardage/meters this reticle is supposed to be rated for. Or maybe you can help fill in the blanks on these images with your own measurements.

Since this information exists nowhere else on the net, and with so many scopes having this reticle installed, it would be a huge help to all those who find their selves with one of these in their hands.

If nothing else, these can be considered the only known measurements in existence on this reticle so far. May it help the next person that is trying to hunt down information about this reticle design so they too don't waste a week of their life in looking.

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: August/23/2010 at 00:44
djwarner View Drop Down
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Hi keo,
 
I just bought an NCStar 6-24x50 scope with the same reticle and I appreciate the photos.
 
NCStar has a PDF available on their website. But before you go to get it, it isn't worth the powder to blow it to hell.
 
I took measurements from your photos and built a spreadsheet. The above worthless pdf states that each smaller horizontal line is 25 yards farther than the one above for objects of a known width (they used 18" in their example). If this were the case, there should be some subject width that would yield results in the proper proportions. From what I can tell, there is no such width.
 
Next, I looked at the ratio of the imputed distances from line to another and was surprized to find the ratio was constant from one line to the next. Depending on how accurately you measured your 36" at 100 yds and how accurate the magnification scale was, the ratio was 120%-125%. IE if the top line was 25 yards, the next line would be 25 x 1.25= 31.25. The third line would be 31.25 x 1.25 = 39.0625 yds. The forth line = 48.828. The fifth, sixth and seventh would be 61.03, 76.3, and 95.36 respectively.
 
Needless to say, this makes the scale useless without calibration at each scope magnification. But it explains why no one else has come up with  a better "How To".
 
 
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: August/23/2010 at 04:11
keo View Drop Down
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Thanks for the further input. I wouldn't say that it is totally useless, but it would take a concerted effort for anyone to learn its distance measuring properties for one or two magnification settings. I had been to the NCStar website and they had a link to reticle documentation, but at the time I was searching it dead-ended into a "coming soon" page. I went and got the PDF you talked about. True, not very valuable information. :-) Certainly the tic-marks could be learned and put to use more easily than the range-finder area. Looks "cool" though, doesn't it? Isn't that what matters to most buyers? Big Smile

Aside: I only got the scope because I have had a problem with feral farm-cats in my area destroying the natural food-chain. In order to undo the drastic imbalance caused by irresponsible pet-owners I've taken it upon myself to help increase the local opossum, fox, raccoon, and skunk population by feeding hoards of them every night (50 to 60 assorted critters every night, surprisingly many of the different species will eat out of the same plate at the same time). In the hopes that they would displace all the cats. I hadn't heard an owl in over 15 years due to cats destroying (not eating) all their native food sources. 

The cats had a habit of always coming into my yard at night. Difficult to shoot with a non-illuminated scope. This one has served its purpose well. Got rid of at least 17 of the lousy cats this year so far. And just last week, while out feeding (and hand-feeding some of) the critters and their pups, there was actually an owl in a branch only 5 ft. above where I stood. It was watching for any mice or voles that would scamper from crumb to crumb dropped by the more glutenous eaters. Those mother raccoons sure were curious about where the owl would land to subdue some prey. Sniffing all over where it had landed after it flew back up onto its perch. Though I was concerned about some of the smaller raccoon pups being attacked by an owl. The owl was on the smaller side so it probably thought the raccoon cubs too large. If nothing else, they got an interesting lesson about owls. They even let me pet them. When feeding out of my hand, they don't just grab the food, they grab my hand and pull it closer to them to eat out of it. It's a pretty special feeling when a wild animal mother trusts you that much with her offspring.

I guess my rebalance-the-foodchain plan is working.

One man's "varmint" is another man's "friend and family".

I've met of lots of people with family that are nothing but varmints.

Big Smile

p.s. I don't worry about rabies. If you check the stats of rabies infections, you have a much higher risk of catching rabies from any cat than any wild animal.




Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: August/23/2010 at 17:06
djwarner View Drop Down
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It may not all be worthless. From you pictures the tick marks on the crosshairs appear to be 5 MOA at 8x magnification. 
 
From the NCStar PDF, I had assumed that the 5 MOA would occur at 6x and my scope would go up to 24x. That would make each tick mark 1.25" at 100 yards.
 
I set my Marlin 30-30 to hit 3" high at 100 yards. Here is the impact elevation at various yardage along with the resulting aimpoints in tick marks:
 
Distance    POI   POA in tick marks
 
50 yds      +1.25"    + 1.67 ticks
100yds     +3.00"    + 2.40 ticks
200yds     +0.00"    + 0.00 ticks
250yds     -3.85"     - 1.25 ticks
300yds     -11.15"   - 3.00 ticks
 
As you can see even without estimating distance for ranges up to 230 yards, centering the crosshairs on the kill zone for a deer or wild boar will put you within the 3" kill radius desired for these animals.
 
I'll have to update the table once I calibrate my scope.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: August/25/2010 at 23:16
djwarner View Drop Down
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OOPS,
 
Began calibrating my scope and found that the reticle ticks on the crosshairs measured 5 ticks at 10x magnification.
 
I went back to the spread sheet and upon double checking my formulas, I found and error. When I corrected them, distances began making more sense. Unfortunately, to start at 100 yards, the known width had to be twice as wide as the crosshair gap. Since you measured about 36 inches at 9x, that would measure 40 inches at 8x. This would mean it would take an 80 inch wide target to range find 100-275 yards. Not a very useful measurment if you ask me.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: August/26/2010 at 02:16
8shots View Drop Down
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Most of these reticules work on the presumtion that one of the factors are known. So if you want to estimate the distance you need to know the target size. If you want to know the target size you need to know the distance.
Normally we use it to range distance to objects of known size.
On my scope I measure the distance with a rangefinder, I then draw a chart of the target size in relationship to the reticule. When I encounter an unknown distance I view the target of known size and read of my chart the distance.
Mostly on scopes the reticule is on the 2nd focal plane, meaning that the reticule changes as you zoom in and out.
So you will need separate calculations for each zoom point such as 10x 8x 6x etc.
If you want to use the reticule for holdover points, then you need to place a 1 inch grid paper at 100 yds and mark on a chart where each reticule falls and then convert to MOA.
The next step would be to determine the trajectory of your bullet and to match that at known distances with your reticule.
So you can now range a target of known size. Let us say you find it to be 270 yds. You know your bullet drops 12 inches from a 100yds zero. You  know that your reticule 4th down is say 12 4MOA. So you use the 4th reticule down and you should hit the target. In theory anyway!!
 
Nothing beats a bit of trial and error at the range to put it all together.
 
 


Edited by 8shots - August/26/2010 at 06:57
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: August/26/2010 at 02:29
sscoyote View Drop Down
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8 SHOTS, I think u got your math flipflopped somewhere. If the bullet drops 12" at 270 yds. that would be 4 MOA, which would be a reference of 1/3 of your 12 MOA stadia line.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: August/26/2010 at 06:58
8shots View Drop Down
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Originally posted by sscoyote sscoyote wrote:

8 SHOTS, I think u got your math flipflopped somewhere. If the bullet drops 12" at 270 yds. that would be 4 MOA, which would be a reference of 1/3 of your 12 MOA stadia line.
 
Oops you are right. Typed faster then my brain could think. Thanks for picking that up.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: August/26/2010 at 23:03
djwarner View Drop Down
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8 Shots, Thanks for your reply. I believe you were only privy to half of the conversation. We were discussing the PDF found on NCStar website describing this reticle.
 
Also, the 30-30 rifle is not known as a long distance shell. In order to realize the maximum usable range, the gun is sited in to shoot +3" (high) at 100 yds. With this trajectory, the bullet crosses zero drop at 200 yds and only drops to -3.85 inches at 250 yds. This is done in lieu of using a BC dial on the scope. So I know where the bullet will be at various distances allowing for Kentucky windage. What I was trying to do in the calibration was to translate this windage into tick marks.
 
As for the choke lines (stadia), we were trying to make sense of the NCStar documentation. First point was to estimate the magnification required to yield a cross hair tick mark value of 5MOA. For keo's scope it worked out to 8x; for mine it worked out to 10x. From keo's images the width of the top stadia line is twice the 8 tick marks on the crosshairs. Thus, for the top stadia to represent 100 yds, the width of the target would be about 80 MOA (inches).
 
The NCStar PDF is riddled with errors. I'm going to except it to show examples.
 

The 2nd part of the Range Finder Reticle is the range finding choke that is below the main reticle (This is referring to the curved lines and stadia lines).

The range finding choke is calibrated for the lowest power zoom setting for the particular scope model.

The range finding choke is a pair of curved lines that taper down. The choke has a series of horizontal lines that correspond to a specific range in yards.

The range finding choke is calibrated for the average sized human shoulder width of 18 inches. So, you will be able to quickly do range estimation for human sized silhouettes or 18 inch wide targets.

 
The document listed the distance for the various stadia lines as 100, 125, 150, 175, 200, 225 yds.
For the respective line widths, 18 inches would have to cover 80 MOA. For my scope (calibrated at 10X) this would require a magnification of 44x - not my scope's lowest power zoom setting of 6x. Since keo had read the PDF, I was simply informing him of my findings.
 
BTW after calibration, my Kentucky Windage at 24x magnification worked out as follows:
 
Distance    POI   POA in tick marks
 
50 yds      +1.25"    + 1.25 ticks
100yds     +3.00"    + 1.375 ticks
200yds     +0.00"    + 0.00 ticks
250yds     -3.85"     - 0.70 ticks
300yds     -11.15"   - 1.70 ticks
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: August/27/2010 at 03:46
keo View Drop Down
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Dang, that's some pretty thorough investigative work you've done. Hunting-cap's off to you for all that 'cipherin'. This will be an excellent reference (and debunking thread, yes I spotted those grievous errors in the PDF) for anyone else who finds themselves with one of these reticles on a zoom scope. I'm going to just simplify it for my own purposes, knowing that the top-line is about 1 cat-length at 30 ft. My reference unit-of-measure.

I'm glad those photos of the reticle can be of some use. As they were actually taken through the eyepiece. I only used my image editing tools to increase the contrast greatly to turn them into crisp B&W line-drawings. Or what appear to be line-drawings now. Other than that, they are accurate as the eye sees them. Thanks again for all the input and sleuthing. Could be very valuable info to long-range shooters trying to make use of one.

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: August/27/2010 at 05:10
sscoyote View Drop Down
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I remember seeing that reticle somewhere in Wikipedia. They had a tank bracketed lengthwise in the lower stadia, since the subtensions were so wide. Personally i don't see any practical use for that part of the reticle, unless you're ranging long distances at large tgts. If u use it at 9x, then u just have 4 4.3 MOA repeating interval units to use for downrange zeroing and rangefinding, and that part of the reticle would be much better for rangefinding purposes. Should work well enough for 17.2 MOA total trajectory compensation.

Edited by sscoyote - August/27/2010 at 05:12
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/03/2010 at 00:22
djwarner View Drop Down
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Finally got to the range with a calibrated target and distance. It turns out the Calibration Magnification for my scope is 6x not 10x. My previous error came try to measure a 2.5" target at 40 yards off hand. At the range the target was several time larger and I had a steady rest.
 
Here is the math I worked out:
 

Let me preface the following with definitions:

 

MOA means minute of arc or 1/60th of one degree. It is an angular measurement. One MOA at 100 yards will correspond to a target 1.047” wide.

 

For any target at any distance, you can calculate it’s MOA as follows:

 

Actual MOA =    Target Width in Inches       x         100 yards

                                1.047”          x       Actual Distance in yards

 

 

Since the scope have a variable zoom magnification where the image enlarges but the reticule remains the same, you can adjust for changing magnification as follows:

 

Apparent MOA =             Actual Magnification x Actual MOA

                                                Calibration Magnification

 

So, per the formula, if you had an 18” wide target at 100 yards, it would measure 18 Apparent MOA at 6X magnification and 72 Apparent MOA at 24x magnification.

 

Using algebra to combine these two formulas and solving for Actual Distance in yards gives:

 

Actual Dist(yds) =  Actual Magnification  x  Target Width in Inches x               100 yards

                               Calibrated Magnification x      1.047”         x              Apparent MOA

 

Remember, this is geometry and works for any scope. All you need to know is the length of the range finding lines compared to the calibrated tick marks.

 

I had the good fortune of having a Keo's photograph of the reticule and could make an enlargement to obtain vary accurate measurements. 

 

Knowing the target dimensions and magnification used the Actual Distance in yards simplifies:

 

At 6x magnification and an 18” target,   

Actual Distance in yards =                             1719.2    

                                                            Apparent MOA

 
At 24x magnification and an 18” target, 
Actual Distance in yards =                             6876.8    

                                                          Apparent MOA


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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/05/2010 at 16:16
sscoyote View Drop Down
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That sounds reasonable. In other words the reticle was designed to bracket a man-size target horizontally using the "choke" part of the reticle, and they designed it for meters which makes it "intuitive".
 
The thing is though is that guys that buy this optic/reticle aren't going to be ranging a man (truth is 99% won't even know what to do with it anyways). For me, i'd use the vertical stadia lines for rangefinding since the subtension is smaller, and therefore more accurate, and calc. a system for game back to brisket. I never rangefind horizontally on game since that introduces too much indeterminable angular error into the equation. IMO, back to brisket gives the best and most consistent profile for rangefinding.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: January/14/2011 at 21:19
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Hate to dig up this old thread but I've found it very useful in trying to interpret a scope I was recently exposed to. My friend recently bought a Rem 700 SP model. Not an SPS. This is a Dick's Sporting Goods special run rifle. Dark black bluing, floorplate magazine, X-Mark trigger, laminate stock with cheekpiece and 24" barrel in .270. I digress...

This rifle has a Remington badged 3-9x40 scope that has this perplexing reticle in it. Still not sure who is the manufacturer of the scope. It isn't illuminated. I've tried to find info on this scope for the last two weeks and this is by far the most, and most useful, info I've found to date.

I couldn't believe that the funnel shaped stadia lines were useful as it seemed that the known target width would have to be very wide. Too wide for anything normally encountered or shot at.

I don't expect his scope to last long...

Thanks for the effort!!

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