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Duplex Reticle for Range Finding Squirrels

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This is going to be a bit "math heavy", but do not be intimidated, it is very simple calculations that can be quickly done in one's head once you have established some data.

First, lets list a few "knowns" that I have tucked away in my own skull.

I'm going to be working with the values of a Leupold 3-9x40 VX-2 with a standard duplex reticle.. I believe that all Leupold 3-9 scopes using the standard duplex have the same subtention between the heavy portion of the crosshairs. (Subtension refers to the length between two points on a target, and is usually given in either centimeters, millimeters or inches. Since an mrad is an angular measurement, the subtension covered by a given angle (angular distance or angular diameter) increases with viewing distance to the target.)

If you are using a different scope you can just measure the subtention between the heavy portion of the crosshairs by looking at a ruler at at 20yds and noting the distance between the gaps. Multiple the 20yd values by 5 to establish 100yd values for simplification later.

Anyway, the subtention between the heavy portions of the standard duplex reticle at 9 power is 5" at 100yds. I would use this 5" value on deer sized targets of 15" depth brisket to whithers to equal 300 yds. It's a simple ratio equation.



So, how do we use thus to estimate range for a gray squirrel? Let's use the subtention from the intersection of the crosshairs to the top heavy portion @ 9x which is 2.5" at 100yds.

Let's also use 1.5" as the distance from the bottom of the gray squirrels jaw to the top of the head.

1.5/2.5 = .6 

100yds x .6 = 60yds If the squirrels head fills that gap @ 9x, then the squirrel is 60yds away. Simple math that can be computed quickly. If the heads doesn't fill the gap, then the squirrel is over 60yds and you could use some guesstimating to compute those further distance IF you deem it ethical to shoot at that longer distance. If the head fills 2/3 of that gap in the first example, then it is 1/2 that 60yd distance farther, or 90yds. 1/2 the gap and it is 120yds.

If the squirrels head fills the entire gap of the heavy portions @ 9x, then it is 1/2 of that distance, or 30yds.



But, what if the relationship is somewhere in between?

Then, you can dial back the magnification until the head fills the gap from crosshair intersection to the heavy portion of the reticle. If you end up @ 4X, then the distance is 4/9 or .44 x 60yds or 26.4yds, for quick estimation, 4 x 6 = 24 + 2.4,

3x is easy 3/9 or 1/3 of the 60yds distance = 20yds

4x = 26.4 or 26yds as above

5x = 5/9 or .555 5x6 = 30 + 3.0+ .3 = 33.3 or 33yds

6x is 6/9 or 2/3 ( 2x the above value or 40yds)

7x is 7/9 .777 7x6 + 42 + 4.2 + .4 = 42 + 4.2 + .4 = 46.6 or 47yds 

8x is 8/9 .888x 60 8x6 = 48 + 4.8 = 52.8 or 53yds

9x = 60yds as above

Once these values are established for your particular scope/duplex reticle values, you can make mental notes or tape a slip of paper somewhere convenient for field use.


 
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I just use my "minds eye" knowing drop is 2.58 " at 45 yards thru my Beeman 4x12 Duplex reticle scope. 
Beeman R9 .20 Cal 002.1617545669.JPG



 
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A Leupold 3-9×40 VX-2 with a standard duplex and a fixed parallax at 100 yards seems like a poor choice of scope for squirrel hunting.
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I was merely using a "known" from my centerfire experience. I will be using an adjustable objective scope on the wood stock Air Venturi Avenger that I have pre-ordered. I am shopping for a good used Weaver Classic 3-9X32 with an AO or something of similar quality with either Japanese or European glass at a moderate price point.



As I specified in my post, one can measure the subtention of any scope reticle by viewing a tape measure at 20yds and then multiplying by 5 to get the 100yd subtention for easier calculating. 
 
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Ouch...I am getting a headache ! That is why I carry a simple rangefinder
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I can't see spending $$$ for a range finder when I have one built into my scope. It's not as complicated as it seems once you get used to the trajectory of your rifle and the subtention in the duplex reticle. One less thing to carry and near instant range finding in the sight picture.

Sighting in for a + or - 3/8" PBR out to 50yds will make 99% of the shots on gray squirrels I am likely to encounter will be a quick mental calculation.


 
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Take a deep breath ... come to the conclusion a Duplex reticle has no place in air gunning out side of paper punching or shooting at known distance.

Buy a mil-dot type scope in the price point you can afford. IMO a SFP ( second focal plane ) having a retical that does NOT change with X power adjusted is the more useful for various use situations and getting accustom to using hold over.



Many will say FFP !!! and IMO that is not true being a FFP is damn near useless in seeing hold points at low X power ( too small to read & use ) and at high X power too thick for precision shooting.



Best to find some friends with differing scopes and try some to see what works for you while understanding whats been said above.



JMO ...

Scott S


 
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A rangefinder is a necessity when using an airgun for hunting for humane kills. A lot more critical as compared to Centerfire rifles.

The only exceptions I know of is to use a very precise moderate to high magnification scope with a large parallax wheel with perfect numbered corresponding yardage labels, or if you are darn good enough to use reticle substensions to measure known size targets to know the yardage how snipers do. With airguns the trajectory and drop is so great that precision is very critical. It may be even considered irresponsible to hunt without a rangefinder when shooting airguns.
 
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Ouch...I am getting a headache ! That is why I carry a simple rangefinder
Click to expand...

I can't see spending $$$ for a range finder when I have one built into my scope. It's not as complicated as it seems once you get used to the trajectory of your rifle and the subtention in the duplex reticle. One less thing to carry and near instant range finding in the sight picture.

Sighting in for a + or - 3/8" PBR out to 50yds will make 99% of the shots on gray squirrels I am likely to encounter will be a quick mental calculation.

Click to expand...

Understand completely, but my old brain can't do that much math in my head as quickly as my rangefinder can. Not knocking your methods in any way, more power to the younger brains that can figure these things out...actually quite impressive, but us old guys need simpler methods, that's all
 
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A rangefinder is a necessity when using an airgun for hunting for humane kills. A lot more critical as compared to Centerfire rifles.

The only exceptions I know of is to use a very precise moderate to high magnification scope with a large parallax wheel with perfect numbered corresponding yardage labels, or if you are darn good enough to use reticle substensions to measure known size targets to know the yardage how snipers do. With airguns the trajectory and drop is so great that precision is very critical. It may be even considered irresponsible to hunt without a rangefinder when shooting airguns.
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Just so happens, I am "darn good enough at it".

I'm no stranger to pronounced trajectory drop seeing as how one of my favorite squirrel rifles (when my eyes were younger, I will be 71 years old this October) was a .36 Tennessee mountain rifle Flintlock shooting subsonic .350 round balls. I kept the Mv subsonic to prevent meat damage. A .350 round ball at 1200-1400 fps is a horribly destructive projectile on small game. Quite gruesome even with head shots. Actually, the reason I went to a subsonic .36 flintlock was that getting a 6-squirrel limit was too easy with a shotgun or scope sighted .22rf. I was disappointed if I came in with less than a limit with any type of "suppository gun". If however, I managed to bag 2 or more gray squirrels with my stone ignition charcoal burner, I felt like a really accomplished something.



Consider this: If I adjust the magnification to where the crosshairs to heavy post subtention equals 1 1/2" at 50yds and subsequently, post to post @ 25yds, given the data in the trajectory table I posted earlier, at any distance in between 20 and 50yds, I will be less than 3/8" above or below LOS. Seems plenty ethical to me for me to hold vertical center of the head under the ear at any distance in between 20 and 50yds.

On thing nobody on this forum seems aware of is the affect steeply angled shots have on trajectory. At least nobody has mentioned it thus far. I'm pretty darn good at doping that out too.
 
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Understand completely, but my old brain can't do that much math in my head as quickly as my rangefinder can. Not knocking your methods in any way, more power to the younger brains that can figure these things out...actually quite impressive, but us old guys need simpler methods, that's all
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LOL LOL LOL, I'll be 71 years old this coming October.
 
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1 MOA Calculation

(MOA = minute of angle)

How to calculate the 1 MOA for any target distance or range in inches.

  1. Calculate the distance or range to the target.
  2. Convert this number to inches.
  3. Double this number of inches. (= Diameter of Circle)
  4. Use Pi, 3.14159 times the number in step 3. (= Circle Circumference)
  5. Divide this number by 21,600. (Note 21,600 = minutes in a circle, 360 degrees x 60 minutes in one degree = 21,600)
    [/LIST=1]

    This is the 1 MOA in inches for the target at that distance or range.

    Example:
    1. 100 yards to target.
    2. 100 x 3’ x 12” = 3600” inches to target.
    3. 3600” x 2 = 7200” inches. (= Diameter of 100 yard Circle)
    4. Pi 3.14159 x 7200” = 22,619.448”. (= Circle Circumference at 100 yards in inches)
    5. 22,619.448”/21,600 = 1.04719”. (= 1 MOA at 100 yards)
      [/LIST=1]

      This number is then rounded to 1”.

      MOA = an angular measurement at a specific distance or range or in layman terms a very small piece or section of the circle circumference.

      Older than dirt, 82 in 5 days!
 
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1 MOA Calculation

(MOA = minute of angle)

How to calculate the 1 MOA for any target distance or range in inches.

  1. Calculate the distance or range to the target.
  2. Convert this number to inches.
  3. Double this number of inches. (= Diameter of Circle)
  4. Use Pi, 3.14159 times the number in step 3. (= Circle Circumference)
  5. Divide this number by 21,600. (Note 21,600 = minutes in a circle, 360 degrees x 60 minutes in one degree = 21,600)
    [/LIST=1]

    This is the 1 MOA in inches for the target at that distance or range.

    Example:
    1. 100 yards to target.
    2. 100 x 3’ x 12” = 3600” inches to target.
    3. 3600” x 2 = 7200” inches. (= Diameter of 100 yard Circle)
    4. Pi 3.14159 x 7200” = 22,619.448”. (= Circle Circumference at 100 yards in inches)
    5. 22,619.448”/21,600 = 1.04719”. (= 1 MOA at 100 yards)
      [/LIST=1]

      This number is then rounded to 1”.

      MOA = an angular measurement at a specific distance or range or in layman terms a very small piece or section of the circle circumference.

      Older than dirt, 82 in 5 days!
Click to expand...


    1. 1 MOA. There are 60 minutes in each degree therefore 360 x 60 = 21,600 MOA in a circle. There are 60 seconds in each MOA, there fore 21,600 x 60 = 1,296,000 SOA in a circle.

      Distance has no bearing on the literal meaning of MOA. These values can be used to calculate the distance of the chord of the arc at any given distance. It just so happens that 1 MOA = just over 1" chord of the arc at 100yds.

      MOA? SOA? If we can't understand what they represent, then I guess we're just SOL.

      LOL
 
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Well, I guess I kind of got lucky. I missed out on the used Weaver Classic 3-9 x 32 AO deal, but that might have been a good thing.



I could not find any lower priced scopes that didn't have confusing "cluttered up" reticles so I ended up biting the bullet and ordering a new Leupold VX Freedom 3-9 x 33 EFR.



It has a simple duplex reticle that will be ideal for ranging shots to 50 yds. The subtention at 9X will have a 1 1/2" squirrel's head filling the gap above the crosshair at 50yds and filling the entire gap between the top and bottom posts at 25 yds. The computed trajectory of the FX Hybrid slug will be + or - 3/8" from 20 to 50yds, + or - 1/4" if I use higher rings.



Quick and easy BDC without all the clutter.
 
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In my first version Ultimate Sniper book by John Plaster he goes thru all of this you are sharing with everyone. A man’s head that fits perfectly within the subtensions at a certain power level(on a simple duplex reticle)meant he was a certain x amount of yards, depending on the zoom power setting. Thanks for sharing.



i actually purchased that book back in the early 90’s mainly for scope knowledge and how to get the best use.out of a scope.
 
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In my first version Ultimate Sniper book by John Plaster he goes thru all of this you are sharing with everyone. A man’s head that fits perfectly within the subtensions at a certain power level(on a simple duplex reticle)meant he was a certain x amount of yards, depending on the zoom power setting. Thanks for sharing.



i actually purchased that book back in the early 90’s mainly for scope knowledge and how to get the best use.out of a scope.
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Yep. Unless the man is Pinhead or Mr. Potato Head. It is a useful approximation for range estimation. Such has been used for deer hunting for a long time, using spine to belly distance on deer but sizes do vary so how absolutely accurate it is I'm not certain. It did seem to work very well for John Plaster.
 
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In my first version Ultimate Sniper book by John Plaster he goes thru all of this you are sharing with everyone. A man’s head that fits perfectly within the subtensions at a certain power level(on a simple duplex reticle)meant he was a certain x amount of yards, depending on the zoom power setting. Thanks for sharing.



i actually purchased that book back in the early 90’s mainly for scope knowledge and how to get the best use.out of a scope.
Click to expand...

I find all of the cluttered whiz-bang new reticle to be distracting. To much to digest in the heat of the moment. I believe in the KISS theory. Keep It Simple Stupid.

Marketing! I had some on here admonish me for not using all of the new technology that is being marketed as "must have", saying it is "unethical".

I once shot a red squirrel in the neck at 245yds with my .280. It did take me 2 shots to get the range though..
 
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