Leupy B & C reticle

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bacova

New member
I've been thinking about this for a while, now somebody tell me why it won't work for calculating the range marks on reticles like the Leupy B&C, Nikon BDC ETC.

These scopes have marks for 300, 400, 500 yds etc, but here's no way they can be accurate for whatever caliber you happen to be shooting, they're just approximate, we all know this.

My shooting range, although well laid out with good solid benches, concrete slabs, a roof etc, is only 100 yds. I calculate a 200 yd zero for whatever bullet I'm shooting by finding the BC, the average velocity and using the bullet weight. Using ballistic software I determine the holdover for 100 yds, zero my scope to this mark and know I'm zeroed for a 200 yd POI. I think we all use this method if we don't have access to a 200 yd range, but want a 200 yd zero.

Why won't this method work for calculating the actual range to zero for the marks on the B&C, BDC etc?

I have a 4.5 x 14 Leupy B&C on my 25-06. Using my ballistic software I find the 100 gr Sierra it likes, which has a BC of .355 and a velocity of 3200 fps, needs to be 1.2" high at 100 in order to be on at 200. The software also says it needs to be 3.3" high at 100 to be zeroed at 300, 5.9" for 400, 7.3" for 450 etc.

I feel like I can take a large target, at 100 yds, and shoot a group aimed at the center dot of the target, but using the 300 yd pip in the scope, find the average height of the POI above dead center and calculate where this 300 yd pip is actually placing my bullet at 300 yds. If it's 3.3" high, then I'm dead on at 300. If it's higher or lower than 3.3" I can still calculate where it's actually placing my shot. Say it's only 3" high at 100. This would probably mean the 300 yd pip is placing my shot somewhere around 280 or so and would maybe be an inch low at 300. It would be easy enough to find the exact POI in relation to 300 yds by using ballistic software.

This could be repeated, using the same target and point of aim, but with the 400 yd pip, 450 yd pip etc. If the POI is 5.9" high using the 400 yd pip, then I'm dead perfect. If it's 5" high, then again it's aiming me short of 400, maybe 360, 370, something like that.

Basically, I guess what I'm saying is that by using this method I can find the actual POIs for my 100 gr Sierra when I use the range marks on my reticle. Instead of 200 at crosshairs, then 300, 400, 450 etc using the pips, it may be 200 at crosshairs, then 280, 375, 420 etc in real life.

No matter where the range marks actually place my bullet, as long as I know the range I'm good to go, and I believe I can calculate these points by using the described method.

Does anyone see a flaw in my reasoning?

Sorry for the long post. Thanks Bacova

This is a later addition to this post...
I may need to clarify that Leupold, Nikon etc all say that the way to learn to use these reticles properly is by actually shooting the rifle at various ranges and observing the results. Practice, practice, practice. I feel like my method of calculation, while being no substitute for practice, will negate the need for finding a range where you can actually shoot at 300, 400, 500 etc.
 
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Should get you close, but nothing is better than actually shooting at the known longer range for really being sure about POI compared to POA.

If you can shoot at 300 or 400 yards with the dots, and zero for them, your 100 and 200 yard dots will be close enough for you to hit what ever you want.

Nothing like "knowing" where you are gonna hit, compared to what your ballistic software tells you.

Clayman.
 
I like your thinking Bascova, don't see why it won't work. I have been planning to work up some exact impacts for a couple of my scope/rifle combos this spring. I have a .204 with a Leupold 4.5-14x40 w varmint reticle and a 300 win mag with Leupold 4.5-14x50 with BC reticle. I will try your theory and see how it works. Let me know as the plan develops.
 
I hear you Clayman and agree with you, to a point. If I had access to a range where I could shoot off a bench, using my Sinclair rest and Protector bag and do it at ranges of 400 or 500 yds, then I'd say that's the way to go. Thing is, I don't have access to such a range, most of us don't. I can go to plenty of fields and shoot off a rolled up sweatshirt, off the tailgate of my truck, whatever, at ranges of 1000 yds if I want, but that's not nearly as controlled an environment as my shooting bench, benchrest etc. I don't know that it'd tell me any more definitely than my software does. Plus it'd mean a lot more walking, LOL.

Seriously though, I'm talking about a method of determining POI for someone who doesn't have access to the wide open range and a decent shooting environment.
 
I think you use this method to get close and then test the results when you can get access to shoot at long range.
 
Bacova,
Remember with the B&C reticle you need to determine at what magnification you need to dial the power ring(large or small triangle) for your specific caliber and MV. As per Leupold's directions. If you change the magnification, you will change the p.o.i. for each yardage subtension.
Your #s crunch so it should work for you.
 
Unfortunately there is a flaw in the method Bacova. What u are actually doing when u shoot the gps. at 100 yds. is u are simply confirming the reticle subtension in your scope. U could simply measure it with a yardstick to confirm it. The critical parameters that are not being confirmed are actual trajectory of the bullet relative to calculated. Although the calc'd. BC's of most bullets r close the actual BC will change slightly when it travels down your bore, since lands engraving has an effect upon it, chronograph calibration may be slightly off. Sight height above bore, etc. But the parameter that i've found to be the most important is the actual zero of the entire works. If this is off at the 200, 225, whatever mark this has a significant effect upon the downrange zeros.

If u have access to some places to shoot LR then definitely do so. Conditions changes will make some difference but the higher the BC u shoot the less difference that will make, ESPECIALLY at the shorter ranges of that particular ballistic reticle. Once u go beyond 500-600 yds. then all the variables make a greater difference in external ballistics.

Remember you're not testing the reticle subtensions you're testing actual downrange performance relative to calcd.

This being said, once u calculate the downrange zeros--BOTH HORIZONTAL AND VERTICAL and confirm actual x-hair axis zero ballistic software seems to be very good to 600 yds. or so.

Go here to access the stadia subtensions of that reticle (and others)-- http://www.leupold.com/products/Info_Ballistic_Aiming_System.htm
 
That's what I'm trying to do, determine the actual trajectory relative to the calculated pips on the reticle. They have no way of knowing what caliber rifle the scope will be mounted on, much less the bullet weight, BC etc.

I agree, there's no substitute for testing at the actual ranges in order to see how far the pips are off, but since I don't have a 500 yd range handy I believe I can come pretty close, be much better off than just assuming the pips are what they say they are, which we know they aren't.

Ideally, I'll get a close approximation, which I can later confirm or correct if I ever get to shoot at a real long distance shooting range, like on a military base somewhere.

Personally, I'm not really interested in anything much over 500 yds anyway. If I lived out West and was into long range PD shooting I'm sure I'd feel different, but I don't.

I feel like I can at least get a fair idea of what's going on. There's enough variables I can't control, wind, elevation, barometer etc that anything I can do to help get a grip on the more solid, predictable aspects can't do anything but help.

Thanks for all the input though, everything will be taken into consideration.
 
bacova,
There's one more variable in all this, the actual height of the scope above the center of the bore. The ballistic programs will get you close, if you've actually chronographed your loads. The variable shows up in the field at longer ranges, because the height above bore changes the angle the bullet leaves the barrel in relation to the line of sight.
Without actually firing your rifle at the longer known ranges to verify the drop(and corresponding relation to the range markings in the scope reticle) you are guessing at best. You'll probably be close enough for big game hunting, but I wouldn't count on conjecture for killing pd's or groundhogs, unless you get very lucky!
Good luck1
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Yeah, There's a space in my software app for height above bore, I've already measured it. I've also chronoed all my loads, use it almost every time I shoot.

I'm not doing any PD hunting. Mostly Deer, but with a few days of Groundhog shooting in the summer. I generally use my 204 for that though.

Pretty close to you too. Bath County is where I do the majority of my Deer hunting and all the GH shooting.
 
bacova,
Now I know Dare county has deer! All my old buds from O.I. couldn't wait for September and a few "blow days" to go deer hunting instead of fishing! I spent several years down there looking over a transom /ubbthreads/images/graemlins/smile.gif
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When u shoot your rig @ 100 yds. using the addtl. reticle stadia your bullet impact will be exactly the subtension above your preestablished 100 yd. x-hair axis zero. If it varies, then there's something wrong with the scope. This won't tell u anymore info than running the ballistics program and matching reticle subtension (in MOA or inch per hundred yards IPHY) to the ballistic program prediction.
As far as i can tell there's no way to determine the exact zeros of the stadia besides shooting them, and most importantly the exact x-hair axis zero.

One thing's for sure tho. thinking about this kinda stuff sure is a lot of fun.
 
That's right SS, just exercising the gray cells. Just for grins though, I'm going to test it out at a 100 yd range, record the info and then, maybe next sumer while G'hog shooting, I'll use my rangefinder to lay out a range in a big pasture and see how real world shooting compares to brainstorming.

I'm going to the range this AM to do the short part. I'll let you know the results.

Flyrod, If you spent a few years at OI then we probably know each other. I've been there 36 years. You're right about the blow days, Sept for bowhunting and Oct-Dec for blasting. Remember how half the fleet was always broke down on Labor Day Saturday? Opening day of Dove season, LOL.

I don't enjoy Deer hunting around here though. It's like hunting in the Amazon basin or something, jungle. Gators and Cottonmouths in the wetlands and Diamondbacks & Canebrakes on dry land, plus every kind of biting, stinging bug known to science. I'd rather drive a few hours and hunt the Va mtns.
 
Well, I gave it a try this AM, it turned out to be very windy at the range so I didn't waste a bunch of ammo. The targets are clipped to chicken wire that's hung between two horizontal steel cables, when it's windy enough they'll start bouncing and really screw up a group.

I only shot one round with each of the range marks in the reticle, but they turned out surprisingly well. I had calculated the height over center at 100 yds for each one and marked the target accordingly. Then of course, I aimed every shot at the bullseye, using the range marks for 300, 400, 450 and 500.

I have a level on my scope so I know it was leveled, but apparently the target was canted a little. You can see the bullet holes progressing steadily to the right as they go up. At least until the 500 yd shot, then either the wind got me or my marksmanship went South. I was trying to shoot between gusts, so I suspect the jiggling target finally got me at 500. So much so that I fired a second shot, which was a little better.

I know this doesn't prove anything, especially with only a single shot at each stage, but it was an interesting experiment anyway. I plan to shoot some groups the next calm day we have, see what happens then, when I can average things out.

bctarget.jpg


Like I said, the wind had my target bouncing around, so don't be too critical of my marksmanship, LOL.
 
Interesting. I have the VH reticle on one of my Leupys and have never tested it past 200 yds. I may have to try the same experiment.
 
You know, I've been sitting here looking at today's target, in particular the way the bullets progressivly move farther to the right as they go up. At first, knowing my gun was level, I figured the target must be canted slightly. After looking at it a while I'm beginning to think maybe this is an indication the scope itself is canted. Gun level, but the reticle canted slightly to the right of perpendicular.

I guess it doesn't matter as long as you're using the dead center x-hairs to aim, but as your aiming point moves away from center the cant comes into play and the POI starts moving sideways.

If I'm correct, then whether my experiment proves anything as far as calculating vertical POI or not, it proves worthwhile in showing horizontal movement. Meaning if you have a BDC reticle it's more important than ever to make sure your reticle is perpendicular to the bore (straight up and down), or you may have the range calculated perfectly but be throwing bullets left or right.

Believe me, to my eye this reticle is as perfectly square to the bore as it's possible to get one, but maybe my eye is deceiving me.

Then again, maybe I'm just thinking too much.
 
bacova,
You need to get a calm day and a little more distance to shoot. That will tell you if your groups are walking due to cant of the rifle or crosshairs. Or, you could ask for opinions around the table at RV's after several rounds....you could get all kind of answers! /ubbthreads/images/graemlins/shocked.gif
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"I don't enjoy Deer hunting around here though. It's like hunting in the Amazon basin or something, jungle. Gators and Cottonmouths in the wetlands and Diamondbacks & Canebrakes on dry land, plus every kind of biting, stinging bug known to science. I'd rather drive a few hours and hunt the Va mtns."
That's probably another reason "Little" Charles still lives up here! Yea, I know about the others, too!!
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