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# Range estimation with a duplex?

#1
07-18-2003, 05:33 PM
 Junior Member Join Date: Jun 2003 Location: Red Sea Posts: 7
Range estimation with a duplex?

I know it's POSSIBLE, but anybody here ever range-estimate with a duplex reticle? What kind of accuracy can you get after you practice for a while?
I know mil-dot is definately the way to go for maximum accuracy but I'm interested in seeing how good a duplex can be.
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#2
07-18-2003, 10:16 PM
Re: Range estimation with a duplex?

Sabre,
The duplex reticle can be used for distance estimation to good advantage if the user makes an effort to learn some basics.
I suggest placing an 18" square (plywood, cardboard or whatever) out on a rock, post or easily observed location. Then back off in 100 yard increments and note (write down) what power your scope must be adjusted to, so that the 18" is bracketed by the posts. Way out there use the crosshair and a post. You can get some good data that you can use in the field, at X power if the buck's chest is bracketed then he is about Y yards.

Many reticles are already in 18" separations between the posts (some are 16") so that makes it easier and for some you simply read a second set of numbers on the power ring for the rough distance. This is pretty handy, but a good laser beats it hollow. How accurate, I have never tried to tie that down, I'm guessing 20 yards or less but suspect greater distances will effect this. There used to be some scopes with numbers inside that if you bracket the target a number would be visible in the field of view that approximated the distance. Even used in some sniper scopes (Redfields for instance).

In my experience Mildots are field useable for hunting if you know some dimensions of your critter and have a cheat-chart made up to give you quick readings (some guys can memorize the necessary numbers). Sometimes there is time for Mildot Masters and even a calculator but, bottom line is that stuff can be eliminated by a laser.
#3
07-18-2003, 10:21 PM
 Gold Member Join Date: Sep 2001 Location: North, Texas Posts: 607
Re: Range estimation with a duplex?

Hey Ian, any more updates on the Nikon tactical? I noticed that only the 2.5x10 has the illuminated reticle or am I wrong?
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#4
07-18-2003, 11:05 PM
Re: Range estimation with a duplex?

Texas,
You are correct, only the 2.5-10 has the illumination. Nikon uses a neat system, you can choose between red or green with several brightness levels for each.
The Nikons are working great, the original prototypes have several thousand rounds through them now and no problems.
I took a new 2.5-10 Nikon and a 3.5-10 Leupold LR M1 on a pdog shoot, put them on identical rifles and everyone who shot them preferred the Nikon, unanimous. The Leupold is a fine scope and I really like it, but the Nikon is brighter and better definition to my eyes. Turrets have been excellent, you can say that about both scopes.
How is the weather down in your beautiful city, hot I bet. We are in the mid to upper eighties but usually a nice breeze that helps a bit. Imagine "Santone" is pretty muggy.
#5
07-19-2003, 03:05 AM
 Platinum Member Join Date: Feb 2003 Location: Pueblo, CO Posts: 1,154
Re: Range estimation with a duplex?

Funny you should ask the question about rangefinding with the duplex reticle. I've got an article going into Precision Shooting publications about a guy i met that has manipulated the range estimating system (RES)developed for several of the Vari-X III scopes (Pentax + Burris also offer a similar system as well) for any spp. of game he may be hunting. Ian M explained the system pretty good. This friend of mine has not only used the sytem on game but convinced a friend of his to use it in some of the sniper competitions as well, and since applying the system he has won the Steel Safari in New Mexico twice now.

Leupold's RES is based on a deer sized target measurement, back-brisket, of 16", such that the center-top of post gap of the reticle subtends this measurement @ 100 yds. on the lowest magnification (I believe Burris + Pentax use 18" as a standard). If the deer is smaller than the gap then simply increase mag. until it fits, and voila read the back of the ocular for range. Now if you're shooting at something smaller or larger, a simple recalculation of the power ring is all that's necessary. But as my friend found out, trying to change magnification on the power ring in the field is difficult at best, so what he did was simplify the entire concept by doing the following-- he set the scopes mag. at the maximum point blank range that he could hit a coyote with the load he was using ( let's just assume it's 300 yds. for a coyote-sized target). That would mean that the center-post gap would have to be adjusted to subtend 11" (for a coyote) @ 300 yds. Of course, then all the shooter needs to do is simply bracket the coyote, and if it fits or is bigger then aim center mass and shoot. If the coyote was 25% smaller then he must be 25% farther away, etc. Using this system he has made 1st shot connections on all manner of game animals farther than he ever did before. The neat thing about all this is that the relationship between image size, magnification, and reticle subtension on a variable-powered scope is linear, making calculations fairly simple to perform. Since i've been messing with this, i've probably learned more about my scope than i ever new before, and if you take the time to investigate it you'll find that there are a lot of ways to manipulate the scope to work for your particular needs. It really is fascinating stuff, and if you have Exbal ballistic calculator it opens up even more fascinating possibilities, as he has an option to optimize factory, custom, and even plex reticles for your particular load. Fun stuff.

[ 07-19-2003: Message edited by: sscoyote ]
#6
07-19-2003, 02:30 PM
 Gold Member Join Date: Sep 2001 Location: North, Texas Posts: 607
Re: Range estimation with a duplex?

Thanks for getting back to me Ian, thought I was going crazy trying to find the 4-16 with the illuminated sight. Whats the heaviest recoiling thing you have fired under it?

Mid 80's huh [img]images/icons/cool.gif[/img]. Well after Claudett decided she didn't want to visit Corpus Christi, she gave us waves of thunderstroms, high winds (I've never seen my trees bend over to touch the ground) and low 90's with 100 percent humidity as she hit Victoria.

Cancelled plans to go check out the blinds until the fields dry up maybe 2 weeks [img]images/icons/frown.gif[/img]
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#7
07-19-2003, 03:33 PM
Re: Range estimation with a duplex?

Texas,
Now that would have been some windage! We have twisters up here, even had one recently up in the northern forest. Killed the hell out of a lot of trees, not many people up there so no-one was hurt.
Have shot the NIKONS on .300 Win mag., nothing bigger to date. I am very confident that they will take some abuse, tho.

SS
What your friend is doing is slick and has to work. I made up a simple chart that I make on a label for the Duplex ranging, just happens to be near identical to what you guys are doing.
A lot of what you outlined will also work with mildots. I believe that they are more useful as you have multiple "contant" reference points that can be varied by moving the power ring. Duplex pretty much only gives a person one holdoff, on top of the post as a constant. Mildots enable a similar quick-read and also some very nice holdoffs.

Any preference, pointed posts vs flat-tops?

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