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wind drift????

 
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  #1  
Old 02-04-2004, 03:32 PM
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Join Date: Sep 2003
Location: south carolina
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wind drift????

First off I understand that I am a novice at this. I have been playing the Long range shooting demo on www.shooterready.com tyring to decide if I want to buy it. I can range the targets well enough to get the come-ups for a hit, but can not get the windage. I can call the wind correctly, but can not get the wind deflection converted to MOA. This is suppose to be a shooting simulator not a game. Example: on the first target I range it at 444(it is 420) pull down the chart and adjust up 8.75MOA, The wind is 15mph from 9oclock, the chart says 1.6 inches per 1 mph wind so 1.6 times 15 is 24 inches right?(I know I have to be making a mistake somewhere, I just don't know where) By my calculations 24 inches at 440 yds is 1.55moa, I dial it in and miss. I increase the windage until I get a hit and the correct amount is 4.75moa.
Where am I going wrong??? How does 1.6inches per mph full value wind deflection in a 15mph full value wind equal 4.75moa???

Please help me. [img]images/icons/confused.gif[/img] [img]images/icons/confused.gif[/img] [img]images/icons/confused.gif[/img] [img]images/icons/confused.gif[/img]
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  #2  
Old 02-04-2004, 04:03 PM
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Location: Washington State
Posts: 120
Re: wind drift????

Fd:

That son of a gun is toooo complicated.

Try this one and follow the instructions carefully. Massively easier in my opinion.

D. [img]images/icons/smile.gif[/img]

Horus Simulator
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  #3  
Old 02-04-2004, 04:09 PM
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Location: Sask. Canada
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Re: wind drift????

I am NOT the math guy to help you out, but even I can see that your calculation for MOA of 24" at 440 yards is wrong. One MOA at 400 is slightly over 4", call it 4 inches. At 440 lets call it 4.4. Divide 4.4 into 24" to get the MOA.
On the other hand, you could just hold off about two feet and smack that sucker [img]images/icons/grin.gif[/img]
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  #4  
Old 02-04-2004, 04:59 PM
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Join Date: Oct 2003
Location: Washington State
Posts: 120
Re: wind drift????

Lets use a little thing called a engineering reasonableness test.

I once shot in an 18 mph wind at 200 yards using a 3.2moa hold and 300 yards with about 5.3 moa in that wind.

So that gives us a bench mark.

Now you claim 420 yards, wind is 15mph.

Chart says 1.4 x 15 = 25" (not 25moa, but 25inches and I'm wrong.) 24" seems OK. The engineering reasonableness test says that is OK after you divide by 420 yards. I was using a 100 grain SVHP 6.5mm which is a terrible wind bucker. (BC is about .220)

But 4.75 moa seems reasonable. Too many unit systems!

According to the program, its a .308, 175gr, mv=2635, BC=.495, t=59, h=78, Alt=500.

My Atrag Horus Palm Software says:

Hold up 7.9, into wind 4.7moa

Which the simulator puts nearly dead center on the 12x12 plate in stage A.

Value should be .313 moa/mph. I don't know why they convert back into inches, which should be only used to measure range. Better to work in MOA which is a unit independant of range.

[ 02-04-2004: Message edited by: DMCI ]
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  #5  
Old 02-04-2004, 05:34 PM
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Join Date: Jul 2001
Posts: 1,459
Re: wind drift????

The joys of using programs that don't agree with its own math.

You are not going insane. If the drift is correct at 1.6" per MPH, then at 440yds and 15MPH of full value wind drift is:
1.6 * 15 = 24" of drift
24" of drift at 440yds = 5.45 MOA so 5 would be close enough.

Depending on the round off error in the program, 4.75 is not too bad.

Bottom line is get a rifle any rifle and go shoot. The best teacher is a 22LR and lots of Wally special ammo. After a few bulk boxes, you will have a much better understanding of wind drift and why these programs are a joke.

Chew on this one, 535gr 45 cal bullet leaving barrel at 1100fps to try an hit a target 500m (550yds) away in a switching breeze. Time of flight about 1 1/2 hours or at least soon after the smoke cloud clears or lunch (whichever is quicker).

Jerry
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  #6  
Old 02-04-2004, 06:17 PM
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Join Date: Jun 2001
Location: Palmer, Alaska
Posts: 2,539
Re: wind drift????

Flopduster,
Ian nailed it for you.

How did you derive 1.55 MOA? 1.6" / 1.047"?

You might find this explanation helpfull if you haven't read it already. http://www.longrangehunting.com/cgi-...c&f=2&t=000621


DMCI,

<BLOCKQUOTE><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><HR>Chart says 1.4 x 15 = 25 moa. 24moa seems way too big.<HR></BLOCKQUOTE>

His 1.6" of drift per 1 MPH wind at 440 yards, multiplied by 15 MPH = 24" of drift.

The scope correction, as Ian stated, is
24"/4.40 = 5.45 MOA

To be absolutely precise, you'd then divide that 24" by 4.40, then divide by 1.047" for 5.21 MOA.

There's only a difference of .25 MOA, or at 440 yards, 1.1" if you don't account for the extra .047" per MOA dialed, so it's now big deal.

Double checking your windage correction MOA -

1.047" per MOA * 4.40 = 4.61" per MOA at 440 yds.

4.61" per MOA * 5.21 MOA = 24" corrected for.

Or

4.61" per MOA * 5.45 MOA = 25.12" corrected for.


I would guess your wind speed was about 14.25 MPH not 15 MPH. [img]images/icons/grin.gif[/img]

High winds are a bitch at LR! As you can see, every MPH makes a big difference, and the farther out your target, the larger impact it had.

Let's all say it together now - High BC bullets at high MV makes me a better shot! [img]images/icons/grin.gif[/img]
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  #7  
Old 02-04-2004, 06:28 PM
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Join Date: Oct 2003
Location: Washington State
Posts: 120
Re: wind drift????

and that's why I really like this reticle:





Height of Target(in) x 100
--------------------------- = Range (yds)
Height of Target (moa)

[ 02-04-2004: Message edited by: DMCI ]
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