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understanding reticle subtension

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/06/2015 at 16:09
338LM View Drop Down
Optics GrassHopper
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I have few questions regarding to scope subtension.

1. Are all SFP scope has same reticle subtension? 
    Example
    Let say, I have 2 scopes sightron SIII 6-24x50 and Vortex Viper HS 6-24x50 both has 1 MOA mil-dot 
    reticle. SO, does that means both scope at 12x = 2 MOA and 10x = 2.4 MOA per dot?
2. If that is true... at 20x from mil dots to mil dot = 1.2 MOA ?
3. So what is the correct MOA at 8x? 3 MOA ? That can not be right.
4. Since the scope with 6x zoom, and each mil-dot = 4 MOA and the maximum magnification for both SFP reticle are 20x... does the math changes?    
 
I am so lost with SFP scopes.... (that is why I only own FFP Scopes. BUT! I have to learn it)

Please help!!!

338LM
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/06/2015 at 23:47
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Optics Master Extraordinaire
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This is why I buy First Focal plane, or fixed power scopes... Way to much math!

But for the sake of argument, I believe that scope is "true" at max magnification. or 24x. TChat means a 1 MOA spacing will be 2 MOA at 12x ( wherever that is on the dial, no matter where the numbers are!)

 But it looks like your math is correct. You also need to map your magnification ring to see if where they put the numbers is true... They are notoriously off. See my opening statement...


 And BTW, MOA are not mil-dots. Two completely different way to measure an angle!
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/08/2015 at 05:12
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I actually love the math. I think it's fun to play with for rangefinding and downrange zeroing mostly.
It's important to understand that reticle subtension is inversely proportional to magnification, so as long as the power ring is calibrated relatively correct (most are close), as magnification INCREASES reticle subtension DECREASES, and vice versa. And yes, it is an important concept to understand...IMO.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/08/2015 at 13:42
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Optics GrassHopper
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Thanks SSCOYOTE

Another question (just wanted to be sure of it)...  let's use 6-24 x 50 scope.
scope is zeroed @ 100 yards.
POI at 400 yards, zoom set at 12x   ( 24 / 12 = 2 Mill per dot)

If I wish not to adjust the elevation and only using mil-dot to 
adjust elevation.
Do I only rise the rifle by 2 mil-dot? (2 mil-dot x 200 yards = 400 yards )


Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/08/2015 at 23:25
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Edited by sscoyote - June/10/2015 at 00:11
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/08/2015 at 23:48
NW425 View Drop Down
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Honestly I love math but I hate scope math. FFP is key in my mind. 

Also, like the above poster, angular vs linear calculations, also I feel like we all round to make things easy (like 1moa = 1" at 100 yards), which I feel like that would easily throw off your game at distance because it is not 1" at 100 yards.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/09/2015 at 17:02
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Optics GrassHopper
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I give up.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/09/2015 at 21:18
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