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Can't find my spin drift or coriolis.

 
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  #1  
Old 08-28-2009, 08:56 PM
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Can't find my spin drift or coriolis.

Ok, here goes! Sighted dead on at 100 yds when I move to 1000 I was expecting 7-9 inches of drift to the right, I actually got 0 inches.

Now the technical stuf: 260 Remington, 140 grain Berger VLD @ 2860 FPS. Rifle shoots a constant .5MOA @ 1000 yds or better.

I have checked and rechecked the barrel, scope and reticle for plum ness, Iíve even machined a sliding double V block with a bubble level on top to make sure everything was aligned. I am 100% sure the rifle/scope is correct. According to the computer I should get .6moa right spin drift and .2moa right coriolis deflection for 31deg lat. This is a total of .8moa drift to the right. With dead calm wind I constantly get 0 to .1moa drift to the right, I do have a level on the rifle so I know Iím not canting the gun. I have rechecked the zero at 100 yds numerous times and it is always dead on. Not having to compensate for SD/CE is good but I am wondering why itís not there, any thoughts on this.
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Old 08-28-2009, 09:19 PM
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Re: Can't find my spin drift or coriolis.

Dunno. I confirmed 9" of rightward drift at North Latitude 60.5 degrees last weekend. 300 Win Mag with 10-twist barrel. 210 Berger VLDs.

A 1-2 mph crosswind is all you'd need to cause that much drift at 1000 yds, so it's vital to test in wind-free conditions.
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Old 08-28-2009, 10:25 PM
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Re: Can't find my spin drift or coriolis.

If you have a place where you can shoot both directions, you can see if an unseen wind (up above the ground where the bullet is flying) is affecting you.

I would re-verify my zero at a longer distance. Knowing that your horizontal is perfect (within 2/10moa) or so is very difficult. See if a group at 200-300 yds is still perfect left/right.

AJ
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Last edited by AJ Peacock; 08-28-2009 at 10:32 PM.
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Old 08-28-2009, 10:53 PM
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Re: Can't find my spin drift or coriolis.

Coriolis is affected by bullet path (direction) as well as lat. Shooting East-West or vise versa will cancel coriolis effect. North - South travel will give you the greatest effect.

-MR
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Old 08-28-2009, 11:22 PM
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Re: Can't find my spin drift or coriolis.

Quote:
Originally Posted by MontanaRifleman View Post
Coriolis is affected by bullet path (direction) as well as lat. Shooting East-West or vise versa will cancel coriolis effect. North - South travel will give you the greatest effect.

-MR
The only way to cancel CE is to shoot at the equator. Sorry, not trying to argue. Northern hemeshere is always to the right regardless of direction of fire. The farther north you go, the greater the effects. Southern hemeshere is the opposite. Always left. The farther south you go, the greater the effects. The direction fired in either hemeshere will affect the vertical component of CE but the horozontal is not measurabley different.
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Old 08-29-2009, 04:37 AM
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Re: Can't find my spin drift or coriolis.

Quote:
Originally Posted by Michael Eichele View Post
The only way to cancel CE is to shoot at the equator. Sorry, not trying to argue. Northern hemeshere is always to the right regardless of direction of fire. The farther north you go, the greater the effects. Southern hemeshere is the opposite. Always left. The farther south you go, the greater the effects. The direction fired in either hemeshere will affect the vertical component of CE but the horozontal is not measurabley different.
I was always lead to believe that the coriolis effect had to do with flight time, the speed at which the earth is moving and the direction relative to the shooters line of sight (Azimuth).

I edited my post after looking through some other posts. As it turns out.. my physics isn't what it used to be lol! I don't understand why, but I guess your right. LOL! I'll try to wrap my brain around it some other time ;)
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Last edited by britz; 08-29-2009 at 04:45 AM.
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  #7  
Old 08-29-2009, 06:06 AM
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Re: Can't find my spin drift or coriolis.

Maybe you have a left twist barrel? If so your spin drift would be to the left.
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