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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/11/2007 at 09:22
jackG View Drop Down
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My scopes, all two of them, have z-plex type reticles.   I understand that the scope reticle may be used to range targets.  For example, knowing the approximate dimensions of say a deer's body height, one can estimate the range.  Someone suggested that based on how large the body appears relative the dot spacing allows that range estimate.  Then one can move the dots up or down in order compensate.   Is that right, and if so are there  hunters here who use that feature?  And can the same thing be done with a plex type reticle? 
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/11/2007 at 09:30
Dale Clifford View Drop Down
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Someone suggested that based on how large the body appears relative the dot spacing allows that range estimate.  Then one can move the dots up or down in order compensate

 

basically the way the bas leo system works on the 3's they then add distance markers on the power selector. if you have the distance then dial in or use the amout of estimated hold over.

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/11/2007 at 10:21
RONK View Drop Down
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JackG- you can certainly range to some extent with virtually any plex-type reticle as long as you know the size of your target and the angular subtension of your particular reticle. Keep in mind that said subtension will change as you change magnification settings,( in a scope with a second focal plane reticle, which most variables are.)

 As Dale mentioned, an alternate method is set up in some scopes by the manufacturer in which you adjust the magnification to "bracket" an animal of a given size, within the space between the crosshairs and the top of the thick lower post section, (for example only -it varies among manufacturers; read the manual.).  You then read a value on the power selector dial which indicates the range to that animal, usually represented in yards.

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/11/2007 at 17:36
sscoyote View Drop Down
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All of those systems of measurement are based on the same mathematical formula that is used by the mil-dot guys to range a tgt. Here's the most basic subtension ranging equation (inches to yds.)--

 

tgt. size (") x range of reticle subtension measurement (usually 100 yds.) / reticle subtension (") / quantity of the "subtension unit" tgt. occupies (tenths of the total subtension) = range (yds.)

 

Looks complicated, super-simple to apply. Suppose the subtension of your plex post tip is 5 inches @ 100 yds. post tip to post tip, and suppose u want to set up a system to range a 16" deer back to brisket (Leupold's std.). Just substitute the variables into the equation above to get this--

 

16 x 100 / 5 / 1.0 (deer brackets x-hair to post tip perfectly @ 1.0 subtension units) = 320 yds.

 

Now recognizing that 320 is the tgt. size vs. reticle subtension constant, simply put it into the calculators memory, and finish calculating the ranging chart for that tgt. size--

 

320 / 0.9 = 360

 

320/.8 = 400

 

.7=460

 

.6=530

 

.5 (x-hair) = 640

 

Couple things should be noted here. The further out u go the less accurate the system is, and it all depends on how well u can interpolate between stadia (takes some practice), and if tgt. size changes then that also introduces error. When the mil-dot guys apply the equation their reticle subtension constant is 27.8 (100 yds. / 3.6" = 27.8).



Edited by sscoyote
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/11/2007 at 19:49
RONK View Drop Down
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 Very well-explained, sscoyote!   As you mentioned, the farther out you go, the less accurate your system is to use, because of the difficulty in determining accuratel the true target-to-reticle relationship.  Unfortunately, way out there is where you need accurate range estimation the most.  Still, it is worlds better than taking a wild guess.

 I think a good mil-dot or milling reticle offers an advantage to a plex reticle when employing this system, in that it gives you a much finer series of reference points to obtain a slightly more accurate value. You still need to estimate the target size very accurately for either system to work though, and you still have to perform the math correctly.

 It all makes a good case for passing up the really long shots whenever possible, but is nontheless valuable information to know for those times when you really need to make a challenging shot.

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/11/2007 at 23:06
sscoyote View Drop Down
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Thks. much sir. I tried this just yesterday on a pr. dog, but i estimated his height 1.5 inches shorter than he was, and missed the range by about 80 yds. rather than the 350 lasered. Sometimes it can flat amaze me at how well it works--as u said, within limitations.

 

I was out a couple years ago at a long-range turkey shoot. We were shooting at a bowling pin @ 600 yds. My 3-12X Burris Ball. Plex was 3.1 IPHY upper post tip to x-hair. When we got to the 600 yd.mark i gapped it in the reticle. It occupied .8 of the "subtension unit." I'd measured the bowling pin to be 15" tall, Here's the equation--

 

15 x 100 / 3.1 / 0.8 = 605 yds.

 

I about fell over when i did the calc.--couldn't believe it. I can usually get pretty close on antelope during coyote season with the reticles i use to about 400 yds. or so, but it's sure reassuring to know the laser's right there when i need it.

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/12/2007 at 20:15
RONK View Drop Down
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OUTSTANDING!  That gives a new definition to what it means to know your equipment!
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