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Reticle-Rangefinding Fun at the SP Shoot

 
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Old 06-27-2008, 01:13 AM
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Reticle-Rangefinding Fun at the SP Shoot

In the handgun threads below Ray Prager killed a couple PDs at very long-range with his Contender couple weeks ago. While we were shooting i had the opportunity to play with reticle-rangefinding some. We had set up a 1000 yd. tgt. that day, and while we were shooting somebody asked how big it was. We didn't know, but playing with the mil-ranging formula i knew we could get a rough estimate by leaving the tgt. size as an unknown in the formula. We cranked up the power of his Burris 8-32X BD with Ballistic Mil-dot to 32. I had a 500 yd. silhouette set out to use as a std. since i knew it's dimensions. The MD subtension was calcd. to be 2.1 inch per hundred yds. @ 32X. So i bracketed the big rectangular steel in the optic and took a "mil reading" @ .9 of a mil. I then plugged it into the mil-ranging formula using 2.1" as a "subtension unit" instead of the mil-std. 3.6". Here's the equation--

X" x 100/2.1/0.9=1000

X=18.9"

when we got to the tgt. it measured 19.2. I couldn't believe it. .3" variation @ 1000 yds. That was just amazing i thought.

A doe antelope then came trotting thru the PD town. I quickly lasered her @ 362. I looked thru Rays rig again, and took a quick guess at 1.8 mils. Figuring 14" back to brisket here's what the range came out--
14 x 100/2.1/1.8= 370. Man, this stuff is fun to play with.

At Rich Mertz long-range HG shoot there was a 24" silhouette set at 500 yds. Using the TMR reticle in my 8.5-25X Leup. it reticle-ranged right at 490. That was fun too. This stuff is sure fun to play with--sort of adds another dimension to shooting.

Interestingly i measured 3 of the adult dogs that had been shot and all 3 were 3.5 X 11". Next time i'm gonna play with reticle-ranging them if i can see them in the grass well enuf.
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Old 06-27-2008, 04:26 AM
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Old 06-27-2008, 04:53 PM
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The best part about it is that i'm adapting the mil-ranging formula but simply substituting a different subtension measurement into it to increase it's accuracy and versatility, really to a huge degree. I think a lot of guys just use the Mil-Dot Master with the mil-dot and consequently only touch onto a small part of rangefinding possibilities. Understanding the math behind the simple equation opens up a world of rangefinding with reticles that can only be investigated by researching this concept. Rangefinding with a mil-dot at a smaller subtension gives a more accurate range calculation. The TMR reticle is an excellent example of this. Instead of using the reticle with the std. "subtension unit" of 3.6 IPHY, if the .2 mil lines (.72 IPHY) are used as a subtension unit the accuracy is much better since u can then interpolate between the .2 mil stadia to an accuracy level that is close to .02 mil. Here's the reading i got for the TMR when i ranged the 24" silhouette-- 6.8 .2 mil units.

...and the formula is this-- 24 x 100 / 0.72 / 6.8 = 490

I achieved this by interpolatively breaking the .2 mil subtension unit down into as close to .1 of that unit as possible. That is the true beauty of the system--maximizing it's capabilities. I mean the stadia lines are there. Might as well put them to work.

Last edited by sscoyote; 06-27-2008 at 04:56 PM.
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