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Updraft question ?

 
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  #8  
Old 09-15-2008, 02:31 PM
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Re: Updraft question ?

You've got the situation doped. Scratch the knoggin' a bit and hold a couple of cross hair widths low and let'r rip. I'm assuming you're shooting at a rock here.;)

If it were an animal, there most probably wouldn't be all of that figgerin' time.:confused: If its a large animal you'll be in the "zone". If its a rock, I'd click the .5 moa but then what about the other .1 MOA:confused: Somewhere in this scenario the hitters and missers are defined......
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  #9  
Old 09-15-2008, 04:30 PM
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Re: Updraft question ?

If I understand the situation correctly, the difference is less than 1/4". Yes inch NOT MOA.

.99 cos is about 5 degrees. This = less than one inch difference for a shot at 750 yards. The bullet will however strike higher even though it is less than an inch. With a 4 MPH head wind at exactly 12'Oclock the bullet will strike lower than normal. Again less than one inch. The main air pattern is likely head on with minimal upwards draft. Any upwards draft in this particular scenario will have extreemly little effect on the bullet. Dial it for 750 with confidence and shoot.

One of the places I practice is set up exactly as you describe and at the same distance and typically has a head wind. I was shooting some new bullets the first time I went there and they all shot extreemly low. I thought the wind was wreeking havock on them so I went to another location (very flat and on a calm day) and they all hit with the same setting. Turns out it was simply a lower than published BC. So between mathematics and real world testing you would set it for 750 yards and shoot.

Just my .02
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  #10  
Old 09-15-2008, 05:10 PM
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Re: Updraft question ?

Meichele figgered it exactly as I did. The updraft is likely only affecting the initial part of flight (less impact), the slight downslope and slight headwind nearly cancel each other out. I'd shoot it dead on 750.

Nobody has mentioned whether they feel there would be a slight downdraft at the other hillside. If there is, due to a wind eddy from the headwind coming over that hill, I'd hold up .25MOA to compensate for that.

AJ
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  #11  
Old 09-15-2008, 05:14 PM
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Re: Updraft question ?

Quote:
Originally Posted by meichele View Post
If I understand the situation correctly, the difference is less than 1/4". Yes inch NOT MOA.

Just my .02
I'm bettin' that you can take this 2 cents to the bank and make a buck or two.

When AJ and Meichele agree on something you can surely hang your hat on it!
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  #12  
Old 09-15-2008, 05:55 PM
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Re: Updraft question ?

Quote:
Originally Posted by royinidaho View Post
I'm bettin' that you can take this 2 cents to the bank and make a buck or two.

When AJ and Meichele agree on something you can surely hang your hat on it!

Wow!

Thanks for the vote of confidence!
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Long range shooting is a process that ends with a result. Once you start to focus on the result (how bad your last shot was, how big the group is going to be, what your buck will score, what your match score is, what place you are in...) then you loose the capacity to focus on the process.
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  #13  
Old 09-15-2008, 07:53 PM
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Re: Updraft question ?

I got the .25moa less drop from 742 yards compared to the 750 yards. That was from both exbal and JBM. I did account for the down draft on the opposite side, but about as much as I accounted for the up draft on the shooter's side...none.
My daughter and I drew an illustration of the scenario if anybody wants me to send it to them and they can post it. I'm not smart enough, as the drawing will prove!!!
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  #14  
Old 09-15-2008, 08:16 PM
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Re: Updraft question ?

Quote:
Originally Posted by Bravo 4 View Post
I got the .25moa less drop from 742 yards compared to the 750 yards. That was from both exbal and JBM. I did account for the down draft on the opposite side, but about as much as I accounted for the up draft on the shooter's side...none.
My daughter and I drew an illustration of the scenario if anybody wants me to send it to them and they can post it. I'm not smart enough, as the drawing will prove!!!

I put it in my Exbal (I use .8 BC for the 300SMK) and I get -.07 moa for the shot. (to get finer granularity than .25moa, one must change options in Exbal to custom and select a finer granularity than .25moa, I use .01moa).

I'd recon we all would hit it. When we all agree within 1/4moa, I'd say it's probably close enough.

Bravo, email me the drawing and I'll post it.

AJ
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