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Leupold Varmint Hunter’s Reticle sync

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/24/2007 at 11:11
flint View Drop Down
Optics GrassHopper
Optics GrassHopper


Joined: October/24/2007
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Points: 4
Hi everyone,

This is my first appearance on this forum, so please bear with me if this topic has been already discussed :(.
Please forgive me if I didn't put enough effort to find this info before asking the question. Anyway...

Each Leupold scope with Varmint Hunter's reticle has 2 special markers on the power "dial":
Small Bullet Drop [SBD] and Large Bullet Drop [LBD].

What they mean is quite obvious from the scope manual.

On 4.5-14x scopes the [LBD] marker is on the maximum magnification.
It means on 14x (or to be precise on 14.4 according to the scope specs).

The ratio in numbers between [SBD] and [LBD] is 1.25.
It means that [SBD] is on 11.5x power.

What I'm trying to accomplish is to recalculate the drops (in MOA)
on the maximum power on my 6.5-20x scope, knowing that
the actual maximum power is 19.6.

It means that the ratio between LBD marker and the maximum power
would be 19.6/14.4 = 1.361.

Using this ratio I can recalculate the drops for each horisontal bar on the
reticle at maximum power...

You probably wonder, what exactly the question is ;)

My question is if my assumption that
[SBD] and [LBD] markers are on 14.4x and 11.5x power
is actually correct.

Thank you so much in advance!










Edited by flint
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/24/2007 at 12:36
Dale Clifford View Drop Down
Optics Jedi Knight
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Joined: July/04/2004
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your assumption and the calculations are correct-- however they contain more accurate information than the scope man. while leo says that such and such scope is such and such power on the index setting, their (and others) manufacuring process is not that precise, probably plus or minus 10%. the methodology leo employs is simply the property of sfp scopes to change point of impact with changes in magnification. It is to their credit that there product is made well enough for this to work (within certain moa boundaries). Leo simply defines it, however, a change in a ballistic curve for the particular power and they don't mention the property of "recalibration" and using the LBD and SBD for the same round (ballistic curve) and market it for a "group" of cartridges (probably easier to understand by a wider range of shooters). I believe Zeiss is now using this "spin" in their advertisments of the new Z"s.

regardless of this the easiest way to "recalibrate" is to use a target of known height put at a know distance and take the readings. My mk 4 6.5x20 still "mills" the same even though the mag is 19.6. the leo varmit can be stated in either moa or millradians, --- to the point-- even though I shoot the 4.5x14 varmit and a 6.5x20 I don't believe the manufacturing is uniform between the two products is "tight" enough to transfer on just a calulation, and even if you did, it would only apply to those 2 specific units.

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/24/2007 at 16:30
flint View Drop Down
Optics GrassHopper
Optics GrassHopper


Joined: October/24/2007
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Dale,

Thank you for your reply.
I realize that chasing 2-3 decimals in these kind of calculations looks pretty much ridiculous.
It's just mind discipline to keep the numbers accurate.
I was just following the pattern that Leupold established in the reticle description.

And thank you for confirming that my assumptions are not totally out of whack.



Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/26/2007 at 11:14
sscoyote View Drop Down
Optics Journeyman
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Joined: October/05/2004
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Points: 326
I also would not trust subtension calcs. relative to magnification. What i'd do is go out and measure all the subtensions at the scope's highest power at exactly 100 yds. (do the same for the "1.77 MOA" horizontal axis windage stadia as well), then go back and calculate the avg. % change in subtensions and use that figure as the "std." to recalculate all the subtensions once again. This "avg. std." should be more accurate than actually measuring each of them, and using those measurements individually. It may even provide an accuracy level of .1 MOA--which is really all a guy would ever need, for both reticle-rangefinding, and downrange zeroing.

Edited by sscoyote
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/26/2007 at 16:51
flint View Drop Down
Optics GrassHopper
Optics GrassHopper


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Thank you, Steve!
Sounds like a great plan.
And you don't really have to shoot, just need a good "ruler" at the
certain distance to come up with exact numbers for your own scope.


Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/26/2007 at 20:26
Dale Clifford View Drop Down
Optics Jedi Knight
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Joined: July/04/2004
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 a reliable .1 moa would be really, really nice as it is close to the reticle thickness of many scopes. the reticle thickness could then be used as the offset. (known degree of error)

 

hate to give in to much here as the ffp boys are going to jump all over it.



Edited by Dale Clifford
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/27/2007 at 22:07
sscoyote View Drop Down
Optics Journeyman
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They probably will Dale.

 

I just got ahold of some targets by Thompson Scope Targets of Thompson Target Technologies out of Canton, OH (from Sportsman's Warehouse) that has the std. inch size squares but they're also divided into .25's, that could probably be fairly effectively divided into a tenth of that measurement for a .02-.03 accuracy level, or very close to it. Just something neat offered by the factories, that'd be nice to use to measure reticle subtensions.

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/28/2007 at 09:52
Dale Clifford View Drop Down
Optics Jedi Knight
Optics Jedi Knight


Joined: July/04/2004
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some TSTTTTs huh???  y

yeah should work good for MOA or MIL



Edited by Dale Clifford
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/31/2007 at 09:09
flint View Drop Down
Optics GrassHopper
Optics GrassHopper


Joined: October/24/2007
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I ended up learning that my assumption as a matter of fact was wrong.

Just a day or two before I posted this question here I sent it to Leupold guys.
They didn't reply immediately and I decided to ask here.

But eventually their reply has arrived.

Here it goes.
...the large triangle on a 4.5-14 is on 14 power and the small triangle is on 12 power,
for the 6.5-20 the large is on 16 power and the small triangle is on 12 power...


Bu then

SBD/LBD ratio = 1.25, that you can calculate from their drop numbers in the manual, doesn't make much sense, does it?

14/12 = 1.17
16/12 = 1.33

The calculated from the drop numbers 1.25 is in between.

Well, it just convinces me once again to make my own measures and forget about what they and manual say.



Edited by flint
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/31/2007 at 20:25
sscoyote View Drop Down
Optics Journeyman
Optics Journeyman


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Hey Flint--when u get those measurements post 'em on here, if u would. Be nice to know them. I still can't believe that Leupold didn't calibrate them at the scope's highest power.
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