Home Forums Hunting & Shooting Hunting Optics using duplex reticle for bullet drop

I'm curious to get some experienced opinions on how to use the
duplex crosshairs on a 3-9X scope for long range hunting.
My 30-06 with 165 btsp is zero @250yds, about 3" high @ 100yds,
-4.18 @ 300, -17.90 and -40.00 @500yds, according to shoot ballistics. I do need to go out and bench rest at these distances, but any idea how high to hold the scope sight picture at these ranges by using the reticle?

Aceman.

You can get a guesstimation by how many inches the bottom post to the x of your duplex covers at 100 yards at various powers by looking at where the zero would be on a calculator if you impacted at that distance at 100. The only way to find out for sure is by shooting at that range.

I don't recommend it, but you can use a duplex for varying ranges by adjusting the magnification power, but it will be alot of range work and memorization to be effective with it. Much easier to just buy a proper reticle or do come-ups with target knobs, but regardless range time is a must.

It's sort of funny that you asked as I know someone that hunts here out of a box blind on a ROW across a swamp that regularly has big bucks crossing during the rut. There is water throughout the swamp and most deer cross at sub300 or at a 450yd funnel. From 0 to 300 is no problem (Fast 7 WBY with a submoa 140 NPT load). Luckily his bottom post on the duplex at 12x is zero for the 450yd crossing. His last buck at that crossing was a nice 140" 10, he held the bottom post on the buck broad side(checking a scrap)and dropped him on the spot. That doesn't happen for everyone and he's just lucky his stand placement worked out for his particular favorite rifle/load/scope.

Good Luck

loder

Aceman:I do this with some loads and Leup duplex.Start at 100 and play with the scope to see the subtension at various powers against a 1" grid.


Example with 30/06,165 @2900:Scope a 2-7 Leup:

3" up100; down 4-5 at 300.
At 400,scope is set at 7X;bottom Duplex is your aiming point.
I will bet that your 3-9 set at 7X will be the same.(Note that this rifle has Talley LW,a medium ring really)

Another(faster cartridges): Fixed 6X or 2.5-8 set at 6X:

7mm Dakota-160 at 3100+: 2.75 up at 100;POA at 300;down 9-10 at 400; and bottom Duplex is my hold at 500.Ditto on this with 300 Weatherby and 180 at 3150.With the faster cartridges you do not need a LR reticle to 500 if you prefer not to have one;drop at 400 is easy to determine as you have the BG animal as a frame of reference as well,and 8-10" of drop is not tough to figure.

There are others; you get the drift. Shoot to confirm.Above numbers have been confirmed at the range.

Bob, I lucked out years ago, when I was still hunting elk with a rifle/scope combo.
.300H&H with my 190 gr. load sighted at 200 yds. Was exactly 31 inches low at 500 yds.( yeah I know...doesn't match the charts for that cartridge/load, but I manually shot it at 500 a LOT...it was -31 inches.)
Leupy 1.5-5 X VX-III Distance from Crosshair at top of post on 5x at 500 yds was 32 inches.....dat's right...the width of an elk at the brisket...
A quick glance on target and I could ascertain if the animal was in range, and never had to hold "out of the hair"....
That combo accounted for a number of elk from 75 yds. out to 450yds....
Used the same outfit on a Caribou hunt, got one at what my guide thought was longish range...I used the Crosshair to range jhim...he was 200 yds, no more. Guide wants to know how I figured that...I told him the Caribou is 21 in. wide at the brisket and I used my scope to measure the distance...he never heard of such a thing, but immediately got his antler measuring tape out and checked the brisket!. 21 inches....
Ingwe

Ingwe:Yes; 31" sounds about right to me.

Back before the glaciers receded,I noticed that a 4X Leupold subtended about 8" from crosshair to bottom post at 100 yards(it is really 7.5"IIRC,but close enough).Anyway,at 400 yards tha's 32",and I used to use that figure as a "guide"when elk hunting and the distances got long.

It helped me take two bulls cleanly out around 450-475 yards.On another, the biggest I have ever seen alive in AZ,it kept me from pulling the trigger at what I figured was 550 or so;mostly due to a VERY hard wind at 90 degrees.I knew the drop,but wind was too risky....

With a 300 Weatherby,180 at 3150 or so,zeroed at 300 yards, the aimpoint with the 4X at 600 was the bottom duplex(8x6= 48 inches).Similar to your load but I was zeroed higher ,for 300 yards.This worked for the 7RM and the 160 at 600 yards as well.

You can fiddle with this stuff and get it right;dots make it easier, no doubt,but a plain Leup duplex can get you to 400-500 depnding on cartridge and load.

With a fast 7mm or 300, I don't worry about anything to 400,except whether I should shoot

Yeah Bob....JB got me going on the whole idea of using the reticle as rangefinder a number of years ago...I have found it so effective under normal hunting conditions,for shooting game anything inside ludicrous distance, that I have never wanted for any of the gizmos evberyone uses on TV.
My big game rifles all wore 1.5-5 Leupys for years ( and still do....) so there wasn't any extra math for me to remember...
Now...varmint hunting...dats a different matter...I like LRFs, Dober Dotz, Turrets, you name it! PDs will stand around all day while you fiddle with that stuff...and MOG ( minute of gopher) is a whole LOT smaller than MOE ( Minute of Elk)

Ingwe

Ingwe:I hear you on the varmint "thing";anything goes!Gimme technology!

On BG,I always felt "KISS" was the best approach for me;but piles of varmints,and years of hunting BG with a fixed 4X sort of cemented distances in my head; not that a guy could not be fooled,but if in doubt,a peek comparing the reticle kept you from making errors,or confirmed what you suspected.

Only one big mule deer gave me a chance to use an LR;he was addled by a hot doe,and only 175 yards away.LR not needed.Most give you 5 seconds to kill them,whether they are aware of you or not.They are just slippery.

The technology is good,with time to deploy,but I think it unwise to rely entirely on it...batteries can go dead,LR's may not take a reading...hey it happens! Murphy's Law

I'll second the KISS principle. Like the man said, all too often they simply don't hold still long enough to allow the use of complicated reticles, or LRF's and turrets. Simply bracket him with the whole opening, or half of it, and hold where you need to. Far better to spend what little time you'll have getting into a useable shooting position and managing the trigger break. E

Good thread.

Yep you guys summed it up pretty well,, after shooting the point blank range and hold on fur for years I got caught up in the Shepherds, and subtension/turret game, still have most of them but went to the Leupy Boone and Crocket with a 2.75 inch sight in and use the holdovers when and if I have time for the rangefinder, the 168 Berger VLD in my 7 mag will get me to just over 425 with the crosshairs on deer or lopes,and cover most of my hunting situations but have the holdovers if I need and have Time to do so. Good stuff posted there about real hunting time,, not everyone has the Best of the West scenarios in front of them

Dang Bob, that's EXACTLY what I used to use... Now I've gone the Leupold LR reticle in all my scopes. It's easier and more precise, but the Duplex reticle can be made to work through a bit of experimentation for sure.

Just curious-are dots or TDS or B&C reticles really that helpful if your shots are inside of 500 yds? Say you have a 300 Wby or a 270 WSM sighted in at 250 yards. Your Zeiss scope subtends 4 inches at 100 yards. Out to 300 yards is a simple point and shoot, 300-375 you start to raise the crosshairs (without losing hair), and at 400-500 you use the tip of the duplex. At 500 yards the reticle subtends 20 inches-a 180 gr Barnes at 3200 fps, sighted in for 250 yards, will have around 29 inches of drop. The tip of the duplex on the back of even a Coues deer should get you in the the vital zone. I've done it both ways-I know it's easier to hit a target with a ballistic reticle, but I haven't found that it makes that much different in a hunting scenario. Shot an elk at 350 yards with a B&C reticle using the 300 yard bar, and noticed that the crosshairs were still well below the backline-got me to thinking. What say yea?

E: I've had rutting whitetails cover 50-60 yards while I dropped from standing to a sit..seconds later they were dead or gone.Sometimes a guy does not have much time.

..and a big mule deer that you jump from the head of a canyon picks up a stringer of timber and shows again making tracks....how many yards down the mountain is that??

,,there is not much time as he flits in and out of cover.You have to be ready when,and if,he stops....

Brad: Both ways are quick and sure. The dots and B&C can be a big help.I have shot the B&C at 600 with the 06 and the 165...it lays them in....

rdelius: Well.... yeah!I don't really know the numbersfor 250 yard zero because I have used a 300 yard zero with the 300 Weatherby,300 Winchester,etc. and stuff similar to the WSM; you're right.I zero slightly higher because I am not so squeamish as some about the mid range issue. I want the 300 yard zero;8-10 inches of drop is very easy to deal with for me.But I have been doing it awhile now.....

About a month ago I shot the 300 Weatherby with the 2.5-8 set at 6X,at 500.The bottom Duplex got me into the black easily.At 400 I was down 10".A big mule deer or whitetail is 18-21" top to bottom throught hte chest.A top of back hold will catch him nicely.

A bull elk is larger and I have used app 32" for a mature bull;not all this is vital of course,but you are still on "hair" at 400 with the 300 Weatherby.As indicated,a properly applied Duplex will get you to 500 with the faster cartridges.

The dots and B&C are very helpful to the slower cartridges.

Duplex? Duplex! Doesn't that mean that someone is mixing powders? (Sorry, just a knee-jerk reaction to the rampant misunderstanding that is loose in the world about the OKH Duplex loadings.)

aceman, IMHO the best way to find out how to hold your aim is to practice with your rig and find out what it really does as far as ballistics go. You didn't state what brand scope you are using. What works with one brand may (usually) differs from another.

I love applying the plex-style reticles for downrange zeroing and rangefinding. I had a subtension system calcd. for the 4-12x Burris Mini that was on top a 17 Mach IV XP-100 (both windage as well as elevation). This was my go-to rig for coyote hunting to about 300-350 yds. Plex post tip subtended 2.7 IPHY @12x and was right at 340 yds. for a zero. 300 was .6 and 10 mph wind was 1.3 subtension units. Killed a coyote in just those conditions once a few years back.

It's amazing what can be accomplished once a thorough understanding of subtension in 2nd focal plane optics is understood, and the most accurate system of application is calcd. and tested. Oftentimes all u need is a ballistics program and the optics catalog to establish a preliminary system for testing. I've even seen a 2nd focal plane subtension system improvised in the field once for 2 kills on prairie dogs using a Marlin 22 at 300 yds. and a 3-9x Simmons plex reticle.

Basically what u would need to get out to 500 yds. with that trajectory is a plex reticle that measures (subtends) 8 MOA (40/5 = 8). U're gonna be hard-pressed to find a 3-9x plex reticle that subtends that big. U could improvise and calculate it with a 2nd FP reticle (reticle subtension is inversely proportional to magnification) as Bob suggested earlier, but then u're gonna be way down there for power. The problem with most std. Leupold Duplex reticles of 3-9x and greater is that their plex subtensions r too small to use for any downrange zeroing really. Most of them r set up for their Range Estimating System for a 16" target, so the x- plex post tip is 2.7 MOA or so. They're great for rangefinding, but not so good for downrange zeroing.

Interestingly the best optics for this kinduva' system are the cheaper brands such as Simmons or Tasco, etc. They tend to have wider plex reticles and work well for downrange zeroing using the plex as a ballistic reticle.

It is so fun to play with this stuff. About a month ago i was at a long-range shooting match where we had to engage 4x9" prairie dog silhouettes at unknown distances out to 425 yds--10 tgts. There were large sniper-style silhouette paper tgts. attached to a wooden frame that they used to number each PD tgt. One of the paper tgts. i couldn't get a reading with my laser, but the silhouette tgts. they used were all the same dimension (probably pulled from a sheet of them). I knew the range to the other tgts. so i thought to attempt to "reverse mil" the range using my reticle, that was a couple of dots set up at 4 MOA. I used the mil-ranging formula to calculate the size of the tgt. at 1 range, and then used the mil-ranging formula once again to calculate the range to the unknown tgt., and it worked. The tgt. size calcd. out to 18", and when i later measured the tgts. they were like 18.5" or something like that. Sometimes a thorough understanding of the simple angular math can really reap rewards.