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# Wind drift?

#1
10-19-2008, 08:04 PM
 Bronze Member Join Date: Jul 2008 Posts: 40
Wind drift?

I am new at working on my long range shooting and have been shooting a 150 gr bullet out of a 300wtby with 77.5 gr of IMR 4831, I cant measure muzzle velocity but I am guessing 3150-3200 and I was wondering how much a 10 mph cross wind would move this bullet at 400 yds? How much will a 20 mph wind effect it?
#2
10-19-2008, 08:44 PM
 Silver Member Join Date: Sep 2008 Posts: 175
Re: Wind drift?

This gets complicated (not really...but sorta)

To answer that question accurately I'd need to know the ballistic coefficient of the bullet and its muzzle velocity.

I could probably get close by quesstimating the muzzle velocity...but the ballistic coefficient has to be correct to even get in the ball park.

Edited to add: If I were shooting a 300 magnum (of any flavor)...I'd be shooting much heavier bullets than 150 grains. The 190 to 240 grain bullets will fly WAAAAY better in the wind than any 150 ever made...the heavy (longer) bullets have a higher ballistic coefficient.

Last edited by Ridgerunner665; 10-19-2008 at 08:48 PM..
#3
10-19-2008, 10:32 PM
 Bronze Member Join Date: Jul 2008 Posts: 40
Re: Wind drift?

The ballistic coefficient is .435.
#4
10-19-2008, 11:25 PM
 Gold Member Join Date: Dec 2007 Location: Kuna, ID Posts: 594
Re: Wind drift?

JBM - Calculations

Have fun!;)
#5
10-20-2008, 12:18 AM
 Silver Member Join Date: Sep 2008 Posts: 175
Re: Wind drift?

Figured at 3,200 fps...
2.4 MOA (5.5 inches) at 400 yards in a 10 mph crosswind.

4.8 MOA (20.2 inches) at 400 yards in a 20 mph crosswind.

2500' elevation, 60% humidity, 59 degrees, barometric pressure 29.92
#6
10-20-2008, 05:11 PM
 SPONSOR Join Date: Mar 2007 Location: Wenatchee, Washington Posts: 96
Re: Wind drift?

Quote:
 Originally Posted by Ridgerunner665 Figured at 3,200 fps... 2.4 MOA (5.5 inches) at 400 yards in a 10 mph crosswind. 4.8 MOA (20.2 inches) at 400 yards in a 20 mph crosswind. 2500' elevation, 60% humidity, 59 degrees, barometric pressure 29.92

Might want to check math for the 10mph wind....me thinks 2.4MOA is around 9.6" at 400yds??:confused:
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R-Bros Rifles www.rbrosrifles.com
That which does not kill me......has made a huge tactical error
#7
10-20-2008, 06:46 PM
 Gold Member Join Date: Aug 2008 Location: east central fl. /n.c. pa. Posts: 566
Re: Wind drift?

Quote:
 Originally Posted by mnhiunter2 I am new at working on my long range shooting and have been shooting a 150 gr bullet out of a 300wtby with 77.5 gr of IMR 4831, I cant measure muzzle velocity but I am guessing 3150-3200 and I was wondering how much a 10 mph cross wind would move this bullet at 400 yds? How much will a 20 mph wind effect it?
il'l start the argument.

first off, you have a fine cartridge. you may be aware that the world record for 10 shots at 1000 yds. has been held by that cartridge for about 14 years now.

400 yds.is a cakewalk for that cartridge. wind affect would be minimal unless the trees are bending. the bullet is there, like right now. i would hold over just a little.

that said, your using the wrong bullet for long range in that gun. you will get better results with heaver bullets. certainly initial velocity will be lower, but at longer ranges that will reverse itself. wind affect will be less also. id be using something in the 168 to 190 range. sierra machkings would work fine, and yes they will perform well on game

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