Leupold LR Duplex reticle? Need info.

[Questor]

I'm trying to find information that describes the Leupold LR Duplex reticle. For what kinds of cartridges are the dots graduated?  Thanks.

[sscoyote]

The LR Duplex and LRV Duplex would have had to be designed around the flatter shooting (to 500 yds.) cartridges (at the scope's highest power). The reason i say that is because of this comment they make in the '07 catalog--"With the new LRD, and LRVD reticles a shooter can tailor the reticle to his load by varying the magnification thus altering the subtensions of each stadia."

This means that if you're shooting a 30-30 or some such cartridge that doesn;t shoot as flat as say a 22-250 or whatever then u can match the reticle to the bullet drop. As u decrease power u increase reticle subtension (proportionally, BTW), such that u could alter the power of the scope to make it work. Here's 1 of several ways u could do it. Go out and set big tgts out at 100, 200, 300, 400, and 500 yds. Zero the scope for 200 yds. Now shoot gps. @ all the other ranges (except 100). Now go out and measure the drop at all the ranges. Now convert each drop to it's equivalent 100 yd. drop, i.e. if the 500 yd. gp. avgs. at 50" below center, then that's 10 inch per hundred yds. (IPHY). Do the same with the other tgts. Now go back to the 100 yd. tgt. and put a black dot at each IPHY setting below the center aiming point (500 would be 10 inches down, etc.) Now go back to your bench and with the x-hair centered on the aiming point adjust the scope's power until u get the best "reticle to trajectory fit," and then of curse mark the scope. Now when u're presented with the long shot u can just adjust the power of the scope to your LR zeroing mark, and u should be on at that range. This is 1 of many ways to zero a ballistic reticle to even 100 yd. zeros. Here's a couple other ways--

http://www.burrisoptics.com/pdf/BALLPLEX.pdf

www.ottllc.com/specialtypistols/sp20.pdf

[Thebear_78]

All of the bullet drop compensating scopes do is give you various other aim points at specific distances from the main crosshair.   using this fixed distance you can adjust your zero to most effectively use the aim points at the different distances.  I happen to be a big fan of the LR duplex and the Ballistic plex by burris.     

The Leupold LR duplex adjusts for the first dot is 2.19 MOA below the crosshair,  the second dot is 4.8 moa below crosshair, and bottom aim point is 7.82moa below crosshair.  This is at 9x and is dependant on magnification level.   when you play with the numbers this equals out to.

Long range sight in

range    aim point                        inches of correction
100       crosshairs                                     0
200       crosshairs                                     0
300       first dot                                       2.19moa x 3 (for 300 yards)  = 6.57"
400       second dot                                  4.8  moa x 4 (for 400 yards)  = 19.2"
500       BAP (bottom aim point)                 7.82moa x 5 (for 500 yards)  = 39.1"

They find this works out pretty good for most long range calibers with 200 yard zero.   You can fine tune this even better by looking at drop values with different zero ranges to get the most out of it.  I'll try to explain what I mean  using my 3-9x40 LR duplex on my 325 WSM for an example.  It worked out best with my 325 WSM with a 225 yard zero using 220 PP ammo.

Range                Aim point        inches of correction       Actual drop     point of impact
100 yards           cross hair             0                              +2.3                  +2.3"
200 yards           cross hair             0                              +1.2                  +1.2"
300 yards           first dot               6.57"                        -6.1                   +0.46
400 yards           second dot          19.2"                        -20.7                  -1.5"
500 yards           BAP                    39.1"                        -43.7                  - 4.6"

If I were to just zero at 200 yards using this method it would work out like this

100 yards           Cross hair            0"                              +1.78                +1.78
200 yards           cross hiar            0"                                0.0                    0.0
300 yards           first dot              6.57"                          - 7.9                  - 1.33"
400 yards           second dot         19.2"                          - 23.1                 - 3.9"
500 yards           third shot           39.1"                          - 46.7                 - 7.6"


If used with a 100 yard zero it would adjust for this

100 yards         cross hair             0
200 yards          first dot             2.19moa x 2( for 200 yards)  = 4.38"
300 yards         second dot         4.8moa   x 3( for 300 yards)  = 14.4"
400 yards         BAP                   7.82moa x 4( for 400 yards)  = 31.3"



Just play with the numbers until you find what works for you.

[The Sodbuster]

Now convert each drop to it's equivalent 100 yd. drop, i.e. if the 500 yd. gp. avgs. at 50" below center, then that's 10 inch per hundred yds. (IPHY). 

The relationship between bullet drop and distance is not linear.  The bullet path follows a parabola.  A bullet that drops 50" below the line of sight at 500 yards does not drop 30" at 300 yards.  Thebear_78 posted some good looking drop data that bears this out (pun intended).  Multi-aim point reticles, such as Leupold LRD or Burris ballistic plex take this into account.  You'll notice the distance between aiming points increases as you shoot farther out.

By the way, what's IPHY stand for?

[sscoyote]

Sodbuster you're comment about bullet drop is correct. It is parabolic, but in my posting we're comparing bullet drop using a subtension system optically, and that is linear, i.e. if the bullet drops 50" @ 500 yds. that would be equivalent to 10 IPHY visually by applying a reticle, or as is more commonly referred to as 10 SMOA (shooter's minute of angle). If u have a stadia subtension of 10 SMOA, then that same 10 SMOA will subtend 20" @ 200 yds., 30" @ 300, etc. That's the point i was trying to make to the general public that may not understand the system The Bear mentioned. As i said in my 1st posting there are a number of ways to apply ballistic and rangefinding reticles for downrange zeroing both vertically as well as horizontally. The 1 i outlined is just the simplest system.

Oh yeah, IPHY stands for "inch per hundred yds." == SMOA

1 MOA technically is 1.0472 IPHY. (it's just a slightly different form of angular reference, that is occasionally seen in some ballistics programs, and advertised reticle subtensions).

I see now what u mean by what u quoted from my original posting. That was slightly misleading. What i should have said was that 50" @ 500 yds. is equivalent OPTICALLY with the reticle to 10 IPHY.

[sscoyote]

When i apply a ballistic or rangefinding reticle as a ballistic reticle (such as the mil-dot) i never sacrifice my point blank range for the reticle. I don't care whether the reticle stadia match up to even 100 yd. distances, as i believe long-range shooting should be approached deliberately instead of quickly. Most of mine don't anyway since i use VLD projectiles out of shorter handgun-length barrels 14-18". With these projectiles windage reference is always way off the reticle's design if they even have a system developed for windage--many don't (but are easily calculated). For me shorter point blank range distances can be applied quickly, not long-range, IMO only. It only takes me a second to look up at my range sticker attached to my Butler Creek ocular cover to determine what my vertical and horizontal zeros are for any longer reticle- or laser-ranged distance, once the system is calculated, checked at the range, toubleshot if necessary, and then recalculated using an interpolative system for the "in-between stadia" ranges usually in 25 or 50 yd. intervals. With my system i may not even know what a particular stadia is zeroed for, as my system is designed around interpolative reference where the stadia themselves serve the purpose of reference only most of the time. Where the LRD and LRVD really shine is for accurate windage reference by using the subtension of the plex post tips along the horizontal axis, IMO. Recently i put this reticle on an AR-15 for coyotes and it is the finest intermediate range system i've ever used-- http://www.rapidreticle.com/22lr3-9x32.htm but it  doesn't even come close to even 100 yd. intervals. This reticle is designed around the 22 LR trajectory, but would work very well with any varmint style cartridge for any LR work, once it's adapted to the trajectory of your load.

All this is explained in the aforereferenced article, "Tactical Ballistic and Ranging Reticle Analysis." That article details the systems needed to zero any reticle for any load, including simple plex, subtension changes with magnification changes, custom reticles for other than the designed trajectory, and rangefinding reticles applied as a ballistic reticle. 2nd focal plane reticles have a lot of flexibility built right into them in how they are applied, but it takes some study before the systems are understood, and even more time before they become intuitive.