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Elevation Dope

 
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  #1  
Old 01-14-2010, 11:17 AM
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Elevation Dope

Okay, here is my dilemma! I have shot at 700 yards and 400 yards with my .308. My muzzle velocity is an average of 2612 with a 168 A-Max. I have been using a load of 48.0 grns RL17 with Wolf LR Primers. Everything seems to be spot on for grouping.

Here's the kick in the pants. On the day 12/30/09 we shot 700yrds I needed 22.25MOA up and 6.5MOA to the left. Conditions were less than desirable for this type of shooting but we had to deal with what we had. Temp 24, Baro 28.880, Humidity 71%, Elevation 978, overcast.

Wind conditions, 10-15 head on at the bench with an avg of 12. At the target left to right 8-12mph.

On 1/13/10 temp 29, Baro 28.77, Humidity 63%, Elevation 1079, slight mirage, winds right to left at 90 deg. 410yrds= 8.25MOA and Wind@10mph=2.75 dead on shooting a solid 1MOA group.

Now when I punch these numbers into my balistics program I can't get them to match up. My question is, will a strong head on wind force my bullet to drop requiring more elevation compared to a calm day? The second problem is that for 410 yards I have to leave the BC at the suggested factory BC and drop my velocity to 2600fps from the above avg. of 2612. The numbers are almost spot on. But in those heavy winds, I am 2MOA shy of what I needed to get successful hits at 700yrds. Can somebody help me here?

Dumbfounded,
Tank
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  #2  
Old 01-14-2010, 01:02 PM
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Re: Elevation Dope

I'm not a scientist or a ballistics expert but an example comes to mind is a vehicle (poor example). When driving in a headwind it takes more gas to maintain the same or consistent speed and therefore you get less economy ( in your case drop). Vice verses in a strong tail wind. Sorry about the limited I.Q. answer/example but made sense at the time..........
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  #3  
Old 01-14-2010, 01:36 PM
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Re: Elevation Dope

When I punch it into my Sierra Infinity program it comes up with 22.1 with the perimeters you gave and showing a headwind of 10 MPH so I don't think your drops are off its the program you used didn't account for the headwind because when I punched in the headwind it changed it to match your actual drops pretty closely.
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  #4  
Old 01-14-2010, 02:04 PM
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Re: Elevation Dope

Tank,

A 10 mph wind is equal to about 14.6 feet per second, not enough to affect your drop that much. You could be experienceing some some down draft somewhere? I've expereinced some elevation changes with shooting in head and tailwinds also. Hard to say what all is going on. Shoot on a calm day and see what happens.

Cheers,

Mark

EDIT: 10 mph wind

Last edited by MontanaRifleman; 01-14-2010 at 02:25 PM.
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  #5  
Old 01-14-2010, 02:08 PM
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Re: Elevation Dope

Quote:
Originally Posted by MontanaRifleman View Post
Tank,

A 100 mph wind is equal to about 14.6 feet per second, not enough to affect your drop that much. You could be experienceing some some down draft somewhere? I've expereinced some elevation changes with shooting in head and tailwinds also. Hard to say what all is going on. Shoot on a calm day and see what happens.

Cheers,

Mark
+1 to what montanarifleman said
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  #6  
Old 01-14-2010, 04:37 PM
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Re: Elevation Dope

Well just learned something about my program that I didn't know about before. We do have an input for a head wind. I was under the understanding that straight on or directly behind wind values equaled zero. This is obviously true for left and right windage, but never even though about how it would effect the flight for straight flight. I guess I can say I just learned something. My cousin used my same program and punched that information in and it came up to what it should have been. Problem solved, thanks guys.

Tank
__________________
Matthew 7:13-14
"Enter through the narrow gate. For wide is the gate and broad is the road that leads to destruction, and many enter through it. [14] But small is the gate and narrow the road that leads to life, and only a few find it.

If you find your self in a fair fight, your tactics suck!- Marine 1st Sergeant Jim Ryfinger

Friends don't let friends develop canonitis!-chucknbach

arguing over the internet is like the special Olympics....even if you win, you are still...special!
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  #7  
Old 01-14-2010, 04:37 PM
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Location: cedar rapids Iowa
Posts: 241
Re: Elevation Dope

Wind Direction changes our Vertical Impact......Fact or Myth?
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