Leupold 3x9 duplex range estimation?

[chemist308]

I have a pre-owned Leupold 3x9 x 40mm scope with duplex reticle on my 308. I absolutely love it because it is the only scope I own that never loses its zero. Unlike all the Bushnells I've owned, even when my rifle is dropped if I fall when hunting, that old Leupold scope will not lose zero. But , can these realistically be used to estimate range? I've heard that you can with a duplex reticle, but how?

I shoot at a range with 100, 200, 300, 400, 600 and 1000 yard backstops. To shoot anything past 200, we're required to qualify with minimum 2 MOA accuracy. That said, what is maximum distance these 3x9 scopes could really do that with only 9x magnification?

I'm asking because though I had wanted to replace the thing with a Millet 6x25 x 56mm with Mildot, but now I am short of cash. This Saturday I'll be meeting with the range safety officer to shoot and qualify on some of the further backstops. If you have this scope, what's the furthest you shoot with it? Can you still realistically shoot to 1000, or is 600 pretty much the cut off?

 

[ugaarguy]

I've moved this to competition shooting where more of THR's long range shooters will see this and be able to advise you.

 

[witchhunter]

If you know how far it is between the points of the duplex or between the point of the duplex and the crosshairs at 100 yards, yes, you can. Keep it on 9 power for all distances, it will be twice that much at 200 yards and 4 times that much at 400 yards. 10x at 1000. So if the distance at 100 yards is 6 inches and you know that a deer is 18 inches shoulder to brisket, if the opening in the scope covers the deer top to bottom, it is 300 yards away....

 

[chemist308]

Well, I got qualified to shoot at the 600 yard line today and got my rifle's DOPE down for the load I was using at 300, 400 and 600 yards. I completely understand why folks tend toward higher power scopes with raised and exposed turrets with the MOA numbers when shooting long range.

The question now is what's good for that doesn't cost more than my Browning rifle?

 

[twofifty]

You asked a good question.

As a result I'm going to figure out how many MOA my 2-7x33 duplex reticle's thin crosshair opening covers at 100 and extrapolate from there.

 

[chemist308]

I now believe this is possible. Today I measured 7" between the top and bottom of the duplex on a grid target at the 100 yard bench where I shoot. While shooting at the 300 yard bench I noted the distance was approximately 3 times that, but it was difficult to stabilize enough to resolve on the grid with that level of precision. At 400 yards the grid was almost impossible to resolve. I think making use a marker in 4 or 6 inch increments at the 200, 300, 400 and 600 yard backstops will allow me better resolve it and ensure the accuracy of my initial estimation.

Am I correct assume that if my know my rifle's DOPE with the load I use that I could calculate approximate corrections at ranges in between those numbers or even further, or even estimate holdovers if needed when hunting?

 

[sscoyote]

The plex reticle is for all practical purposes simply a mil-dot reticle with 2 "mil" units in each plane. The only difference is that the subtension (measurement) between the reticle stadia points is different than the std. 3.6 inch per hundred yds. milliradian subtension. Actually in your case yours is very close since you say you measured the subtension between plex post tips at 7 IPHY (I'm assuming at 9X? If you change the magnification the subtension will also change). Now, that means that plex post tip to x-hair axis is 3.5 IPHY. Suppose you had a 10" tgt. that "milled" 1.5 subtension units, then the calculation would be--

10 x 100 / 3.5 / 1.5 = 190 yds.

See how it works?

Is yours a Vari-X III ?

You could probably send that optic in for a target turret installation, and reticle change if so desired, but when going to longer distances an optic with parallax adjustment is usually much more desirable.

 

[chemist308]

@ sscoyote - Thanks. Yes I measured at the highest power. I have no idea if it's the VX3 since I bought it used from the same dealer I boat the rifle new from. Saved myself about $150 that way. Anyway today I picked up a new Leupold VX-2, 6x18 x 40, did similar measurements for it, then zeroed it at 300. That is one sweet scope It's even got the ballistic holdovers for 200, 300 and 500 yards. The 300 one works beautifully for my load, but I zeroed there anyway. It's easy to go back if one keeps a journal...

It's nice to be able resolve the bullet holes at 300 and clearly see the 1" bullseye at 400. Think I'll keep the 3x9 since I still have the data I generated on it. I may way it if I hunt back in PA again.

 

[sscoyote]

Sounds good--that's a great optic I hear. If you're interested in more subtension math, and it's apps. for downrange zeroing and rangefinding then go here and watch my youtubes--

http://www.youtube.com/watch?v=ozEhoNaRi2s