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Reticle Holdover Question

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jason miller View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jason miller Quote  Post ReplyReply Direct Link To This Post Topic: Reticle Holdover Question
    Posted: May/09/2011 at 21:40
So according to Vortex's website, the C3 reticle on my Viper 2-7x32 has a circle with a diameter of 27 MOA at the highest magnification.  My thought was that the bottom where the circle intersects the vertical crosshair could potentially be used as a holdover mark.  But using Vortex's measurement and assuming a radius of 13.5 MOA, does that mean that the center crosshair would be roughly 14 inches higher than the bottom of the circle at 100 yards?  And does that translate to extended range just like MOA accuracy- as in 70 inches of holdover at 500 yards? 

If so, then there's no chance of me using the bottom intersection as a holdover.  I don't have any rifles that drop enough, a range long enough, or any desire to shoot much past about 400.  And a 2-7x32 would be far from ideal if I did.
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billyburl2 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billyburl2 Quote  Post ReplyReply Direct Link To This Post Posted: May/09/2011 at 22:02
What caliber rifle are you thinking of mounting it on?
If it is tourist season, why can't we shoot them?
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jason miller View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jason miller Quote  Post ReplyReply Direct Link To This Post Posted: May/10/2011 at 07:36
My current inventory is a .243, 30-06, and a .338 WM.  None of my rifles would even come close to utilizing a 70 inch holdover at 500 yards. 

I'm really just wondering if my logic on the size of the reticle and how it would translate to distance is mathematically correct.  Can I or can I not infer that a supposed 27 MOA diameter circle in the reticle can be extrapolated out that way?

Obviously the most sure-fire way to test would be to get out and shoot it, but I was hoping someone could chime in on here first.  It will be at least a few weeks before I can get back out to shoot.
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Kickboxer View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Kickboxer Quote  Post ReplyReply Direct Link To This Post Posted: May/10/2011 at 11:52
Your math is correct. Your choice of scope for any of those rifle calibers is questionable unless you are shooting in the 300 max yardage range.  It's not a reticle designed for 500 yard shooting, actually more like 150-200.  Can be used for longer range, but it's difficult.  There are not enough reference points so precision is minimal.  Much depends on how good an estimator you are. 
Measure your reticle subtensions at all power settings using a 36" target marked at 1" intervals and develop a chart.  It will take some time, but if you really intend to use that scope out to 500 yards, you will have to do the homework.  Many have done it. 
Opinion,untempered by fact,is ignorance.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote billyburl2 Quote  Post ReplyReply Direct Link To This Post Posted: May/10/2011 at 12:01
I would suggest JBM ballistics as well. With some chronograph data, they will be able to give you a maximum point blank range. But no amount of advise, or data, is going to replace range time with rounds down range. 
If it is tourist season, why can't we shoot them?
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jonoMT View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jonoMT Quote  Post ReplyReply Direct Link To This Post Posted: May/10/2011 at 12:21
I've found that the farther out I go the more I want to minimize the variables. Using a reticle holdover adds complexity vs. being able to take direct aim at the target through the center of the reticle. If I dial in the elevation correction I can focus on wind, of which we've had a hell of a lot all winter and spring. A good quality scope with well-designed turrets allows for a level of precision that's much harder to achieve with a holdover.

Imagine you're drawing a bead on a buck 400 yards away on a 20 deg down slope and he keeps getting skittish and moves five or ten yards at a time. Meanwhile, the wind is gusting between 10-20 MPH. If you do all your corrections through the reticle, you have to remember what your 400 yard holdover is, remember to hold low (.2 mils or .7 MOA), then work in your wind corrections. The deer's movement doesn't add to the ballistic equation since he's stopping here and there but it does distract the shooter and require shifting your point of aim. Every time, you have to remember where the reticle was supposed to be.

On shots like that, I dial in elevation AND wind (using as reasonable a guess as I can to what it is doing). I want to concentrate on the best point of impact and my trigger pull, nothing else. There's nothing wrong with that scope for a sub-300-yard shot, but I would consider something with good turrets like the SS 3-9 if you want to reach out farther.
Reaction time is a factor...
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jason miller View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jason miller Quote  Post ReplyReply Direct Link To This Post Posted: May/10/2011 at 17:59
Thanks for all the input guys.  My experience with and expectations for future long range shooting are both very low.  The limitations and intended design of that scope are well understood on my part, too.  I was just thinking that if the bottom of the circle would happen to fall into the 4-500 yard range, it would be a handy piece of information to have as a reference point in case a coyote were standing out in a field at long range.  Coyotes and groundhogs are about the only thing a centerfire rifle can be used for in Indiana anyway.  But it looks as though the bottom of the circle will correspond with too far of a range to be worth even trying to find out what that range might be...
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