Leupold RX II

Let others out there hear your view on new and old kit.Give advice on tuning, arrows, archery, and other kit.............

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Postby Guardian » Wed Oct 08, 2008 10:44 pm

Rory,
If I'm not mistaken, there will be no difference for a bow on the horizontal plane, if you have set your sights correctly for the different distances.
Otherwise what benefit will the rangefinder have if 20 yards is not 20 yards ?
What I mean is so simple : a rangefinder should just give you the distances so that you can aim for those distances with your setup bow.
The angle compensation is what makes it interesting, especially when it takes speed into consideration.
I mean it's not like a rifle where you have only one crosshair in the scope and then have to guess the holdover on a distant target.
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Postby Rory » Wed Oct 08, 2008 10:57 pm

True what you say Dirk, its the compensation for incline/decline that makes it so interesting but just as a matter of interest lets try the various settings at say three different distances. 20, 30, 40 yds and see what we get. :roll:
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Postby Harry Marx » Thu Oct 09, 2008 8:07 am

Here's two tables , one for 300 and one for 250 fps.
See how liitle they differ.
I'm drawing one for 200 fps, just takes time...
300 fps
45: 6.5 14.2 21.5 28.8 36.3 43.8
40: 7.1 15.2 23.1 31 39.1 47.2
35: 8.1 16.4 24.7 33.2 41.6 50.2
30: 8.4 17.1 26.3 35.1 44.1 53
22: 9.4 18.4 27.9 37.3 46.9 56.4
15: 9.4 19.3 29.1 38.8 48.7 58.5
10 20 30 40 50 60
-15: 10 19.3 28.8 38.5 48.1 57.6
-22: 9.4 18.7 27.9 37 46 55.2
-30: 9.1 17.4 26 34.5 42.8 51.5
-35: 8.4 16.4 24.7 32.6 40.7 48.7
-40: 8.4 15.8 23.1 30.4 37.9 45.3
-45: 7.5 14.5 21.2 28.2 35.1 41.9


250 fps
45: 6.8 14.3 21.6 29.2 36.8 44.4
40: 7.4 15.4 23.4 31.4 39.6 47.8
35: 7.9 16.5 24.9 33.5 42.1 51
30: 8.5 17.4 26.4 35.3 44.4 53.5
22: 9 18.5 27.9 37.6 47.2 56.8
15: 9.4 19.4 29.2 38.9 48.9 58.7
10 20 30 40 50 60
-15: 9.9 19.4 28.8 38.5 47.8 57.3
-22: 9.7 18.5 27.7 36.8 45.9 55
-30: 9.2 17.4 25.8 34.2 42.8 51.2
-35: 8.3 16.3 24.4 32.5 40.4 48.2
-40: 7.9 15.4 22.9 30.3 37.6 45.1
-45: 7.4 14.1 21.2 27.9 34.8 41.7

ex. for 250 fps, to shoot 40Y at angle of -35, set sight on 32.5
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Postby Harry Marx » Thu Oct 09, 2008 8:14 am

45: 7 14.4 22 29.6 37.4 45.7
40: 7.6 15.6 23.6 31.9 40.4 49
35: 8 16.7 25.2 33.9 42.8 51.9
30: 8.5 17.5 26.5 35.7 44.9 54.4
22: 9.2 18.6 28.2 37.8 47.6 57.5
15: 9.6 19.5 29.3 39.2 49.2 59.2
-15: 9.6 19.3 28.7 38.2 47.6 57
-22: 9.3 18.5 27.6 36.5 45.5 54.4
-30: 8.8 17.2 25.7 34.1 42.3 50.5
-35: 8.3 16.2 24.2 32.2 40 47.7
-40: 7.9 15.3 22.7 30 37.3 44.5
-45: 7.3 14.1 20.9 27.6 34.3 41.1

Hiers tabel vir 200 fps.

incline on the left column, 2 column 10Y, 3rd 20Y etc.
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Postby Harry Marx » Thu Oct 09, 2008 8:16 am

En hierdie is die COS-rule table. Pick your poison lads.

45:7,14,21,28,35,42,
40:8,15,23,31,38,46,
35:8,16,25,33,41,49,
30:9,17,26,35,43,52,
22:9,19,28,37,46,56,
15:10,19,29,39,48,58,
-15:10,19,29,39,48,58,
-22:9,19,28,37,46,56,
-30:9,17,26,35,43,52,
-35:8,16,25,33,41,49,
-40:8,15,23,31,38,46,
-45:7,14,21,28,35,42,
"Dirty Harry"
Elite GTO 72#, 30"
605 gr. GoldTips @ 261.5 fps, 92 ft.lbs
virtual weight about 45 grain
Cam Efficiency 77%
cell 084 267 4429
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Postby robass » Thu Oct 09, 2008 8:20 am

What I am going to try is to find a building , lets say 3 stories high , measure the distance upwards lets say 20 yards (yes I know you may never shoot that high up or down) but for the exercise we will try it ,then range 30 yards away from the base of the building , then range from the 30 yard "spot" to the distance 20 yards up the building , and using the hypotenuse theory the straight line distance to the "target" will be 36.05 yards . BUT , using the true ballistic " bow" setting on the Leupold , I guarentee you it will tell you to "aim" and note i use the word "aim" at about 30 to 32 yards due to the angle . I am also pretty sure that if you aimed at 36 yards you would more likely than not shoot over the top of your "target"

I will post some results once I have tested it on all 3 "bow" settings
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Postby Merv » Thu Oct 09, 2008 8:30 am

:idea:
Last edited by Merv on Thu Oct 09, 2008 9:27 am, edited 1 time in total.
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Postby Rory » Thu Oct 09, 2008 8:38 am

Harry thank you for your info this is excellent :thumb: :thumb:
is this table tailored to your specific set up or a general guide :scratch:
Last edited by Rory on Thu Oct 09, 2008 3:53 pm, edited 1 time in total.
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Postby robass » Thu Oct 09, 2008 8:39 am

You could also take the inverse tangent of Opposite (horizontal) / Adjacent (vertical) to assure that you are at a true 90 degrees from vertical or horizontal depending on your line of sight. For short always remember when you are shooting up or down that gravity will not pull arrow as much. For example: When you are practicing in the yard the arrow is starting out pulling gravity (arching up) so that it will drop into place. When you shot out of a tree toward the ground the arrow is still pulling gravity but it is slower to drop into place because of the lack of stress caused by gravity. If you were to shot an arrow straight down the arrow would pull gravity just as it does in your yard but it will NEVER drop to its zeroed point. Gravity would hold it there for eternity or until it is stopped.
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Postby Harry Marx » Thu Oct 09, 2008 8:42 am

robass, my model says you can aim at 31.27 Y :lol:
I'm eagerly waiting for the result of your exp.

Merv, no, my own model.
I assume you loose about 5 fps over the first 20Ys due to friction, and calc the friciton force that is proportional to the square of the speed.
Then I apply gravity and friction to arrow, in small steps, 3/4 of an inch steps, thats 500 steps per 10Y.
Which I then allow to run to about 60Y.
If it shoots low, program incrrease the angle, if it shoots high, program decrease it, until it hits target.
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Postby robass » Thu Oct 09, 2008 8:43 am

Great Harry , thats a fantastic , detailed explanation .
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Postby robass » Thu Oct 09, 2008 8:45 am

Harry Marx wrote:robass, my model says you can aim at 31.27 Y :lol:
I'm eagerly waiting for the result of your exp.

.


Harry , is this based om my example provided above ?
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Postby Harry Marx » Thu Oct 09, 2008 12:18 pm

Yes robass, 20Y hight, 30Y horz dist, thats 36Y to target, 33.7 degrees down.

Rory, this is theoretical for an arow at said fps, that looses 5 fps over the first 20Y.
There are however another factor which I have not worked into the model yet, that is the effect the arrow's spin has on the trajectory. During the first 20Y or so, the arrow has more friction, it is being rotated faster by airflow, thereafter friction drops an even beome less than a straight fletched arrow.
So no, not REAL. If only robass would do the exp, then I woul know how accurate it is.
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Elite GTO 72#, 30"
605 gr. GoldTips @ 261.5 fps, 92 ft.lbs
virtual weight about 45 grain
Cam Efficiency 77%
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Postby Rory » Thu Oct 09, 2008 4:05 pm

This is all very interesting thanks harry :wink: :thumb:

I had every intention of getting round to trying out the various settings but just didnt get round to it...will be able to next week if no one els does before that :wink:
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Postby Guardian » Sun Oct 12, 2008 9:21 pm

Thanks Harry,
Just as Robass and I worked it out the other night at the club meeting, it makes a difference, BUT for my shooting abilities , I'll discard the differences between 32.6, 32.5 and 32.2 at your example angle and distance (40m at -35). (for 300, 250 and 200fps)
These guys at Leupold are just too clever, they might just confuse the less advantaged thinkers :D
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