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You could make yourself a siloutte and pick some random distances to see how well do.

-Mark

Yes u can use the stadia in a reticle to measure the distance to a tgt. of KNOWN dimension. The best way to accomplish this is to apply the "modified mil-ranging formula." All rangefinding with reticles (stadiametric rangefinding) is based on this simplified equation. Here it is (inches to yds.)--

tgt. size (") x range of reticle subtension (usually 100 yds.) / reticle subtension (") / quantity of gap tgt. occupies between stadia (decimal equivalent) = range (yds.)

...looks complicated, but quite simple to apply--

Example--sounds like u have the NP-R1 reticle (maybe R2?). If it's the R1 then i think the stadia to stadia gap is 1 inch per 100 yds. in that reticle (better check that 1--don't know for sure). Suppose u look at your big bull elk at an unknown distance and u see that he occupies 3 and 1/4 of the 1 IPHY stadia units. Most folks say that the avg. bull elk is 25" back to brisket, but this guys a biggie so lets give him 2 more inches at 27. Now just fill in the variables in the equation--

27 x 100 / 1.0 / 3.25 = 830 yds.

...BUT...it's not really that easy oftentimes. Obviously u need to guess the tgt. size correctly, and guess the "gap" correctly too.

Now let's see how far off u will be if u're off in tgt. size by only 1"--

2600/3.25=800

2800/3.25=861

so as u can see +/-1" gives 60 yds. variation in range estimation, and thats assuming u've guessed the gap accurately to a level of 1/20th of it's subtension (.05).

It should be obvious that as range increases the error increases geometrically.

I've found reticle rangefinding with scopes is fairly accurate to 400-500 yds. and then drops off dramatically beyond that.

tgt. size (") x range of reticle subtension (usually 100 yds.) / reticle subtension (") / quantity of gap tgt. occupies between stadia (decimal equivalent) = range (yds.)

...looks complicated, but quite simple to apply--

Example--sounds like u have the NP-R1 reticle (maybe R2?). If it's the R1 then i think the stadia to stadia gap is 1 inch per 100 yds. in that reticle (better check that 1--don't know for sure). Suppose u look at your big bull elk at an unknown distance and u see that he occupies 3 and 1/4 of the 1 IPHY stadia units. Most folks say that the avg. bull elk is 25" back to brisket, but this guys a biggie so lets give him 2 more inches at 27. Now just fill in the variables in the equation--

27 x 100 / 1.0 / 3.25 = 830 yds.

...BUT...it's not really that easy oftentimes. Obviously u need to guess the tgt. size correctly, and guess the "gap" correctly too.

Now let's see how far off u will be if u're off in tgt. size by only 1"--

2600/3.25=800

2800/3.25=861

so as u can see +/-1" gives 60 yds. variation in range estimation, and thats assuming u've guessed the gap accurately to a level of 1/20th of it's subtension (.05).

It should be obvious that as range increases the error increases geometrically.

I've found reticle rangefinding with scopes is fairly accurate to 400-500 yds. and then drops off dramatically beyond that.

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I have a bull elk on my wall that measures 30" and I confirmed the measurement with a taxidermist who said that is the measurent for most mature bulls. You'll probably get a little variation between individuals, but 30" is the norm.

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so hows that math work out for a regular old mil dot?

Tank

Tank

See where the "reticle subtension (")" is? That variable would then become 3.6", and if somebody had a mil-dot reticle and looked at the same tgt. at 830 yds. right next to this guy who's using the Nightforce NP-R1, here's what it would "gap" in his reticle--

27x100/3.6/x=830

x=0.9 mil.

Now if i were looking at that tgt. with my Nikon Buckmasters mil-dot at 18x (now 2.4 inch per hundred yds. between dots) instead of the mil-cald. power of 12 here's what it would gap in that reticle--

27x100/2.4/x=830, x=1.35 mils--

ONE of the nice things about understanding how to manipulate this formula is that if u have a mil-dot reticle that's cald. for a power that's lower than the highest (mine above), u can "mil" at a higher magnification which allows u to define the edges of the tgt. better--most of the time.

27x100/3.6/x=830

x=0.9 mil.

Now if i were looking at that tgt. with my Nikon Buckmasters mil-dot at 18x (now 2.4 inch per hundred yds. between dots) instead of the mil-cald. power of 12 here's what it would gap in that reticle--

27x100/2.4/x=830, x=1.35 mils--

ONE of the nice things about understanding how to manipulate this formula is that if u have a mil-dot reticle that's cald. for a power that's lower than the highest (mine above), u can "mil" at a higher magnification which allows u to define the edges of the tgt. better--most of the time.

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Oh well--looks like i erred once again-- the NP-R1 is actually true MOA according to the catalog. That means it's 1.0472 IPHY between lines. So u can substitute that figure (subtension) into the equation.

Now here's something that Darrell Holland's teaching his students in his classes that i bet not many r doing to have the most amount of accuracy possible from rangefinding with the reticle. This is actually something i stumbled across myself a few years ago while using the Burris Ball. Plex to range with. When using line stadia for rangefinding the shooter should subtract 1 line thickness for calculating his subtension factor. The reason is that people tend to gap BETWEEN stadia lines not from center to center. It may seem like a moot point, but it could make a difference. I mean u have to use a factor anyways--might as well be as accurate as possible, right?

That means that his subtension factor should be 1.0472" - .065" (thickness of 1 NP-R1 stadia line) = .9822"

Now substituting that into the original equation we now get--

2700/.9822/3.25=846 yds., a difference of 16 yds. (could make a difference--better have a steady rest to range with that degree of accuracy with that reticle at that range at that power).

...now if a shooter had the 12-42 NXS and had the NP-R1 reticle he'd have a unit of subtension of 0.51 IPHY @ 42x which would be about as good as it gets for reticle-rangefinding with any scope maker out there.

Now here's something that Darrell Holland's teaching his students in his classes that i bet not many r doing to have the most amount of accuracy possible from rangefinding with the reticle. This is actually something i stumbled across myself a few years ago while using the Burris Ball. Plex to range with. When using line stadia for rangefinding the shooter should subtract 1 line thickness for calculating his subtension factor. The reason is that people tend to gap BETWEEN stadia lines not from center to center. It may seem like a moot point, but it could make a difference. I mean u have to use a factor anyways--might as well be as accurate as possible, right?

That means that his subtension factor should be 1.0472" - .065" (thickness of 1 NP-R1 stadia line) = .9822"

Now substituting that into the original equation we now get--

2700/.9822/3.25=846 yds., a difference of 16 yds. (could make a difference--better have a steady rest to range with that degree of accuracy with that reticle at that range at that power).

...now if a shooter had the 12-42 NXS and had the NP-R1 reticle he'd have a unit of subtension of 0.51 IPHY @ 42x which would be about as good as it gets for reticle-rangefinding with any scope maker out there.

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