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SPIN DRIFT!....I'm such a dummy

 
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  #15  
Old 01-22-2011, 11:59 PM
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Re: SPIN DRIFT!....I'm such a dummy

When Shooting 500 to 1000+ yards I recommend making the vertical (MOA) adjustments, then the
spin drift(MOA) adjustments needed at that range and them do the actual wind (MOA) adjustments
for the conditions.

This basically sets the zero under a no wind condition before the wind is be added.

There was also the mentioning of mirage. If you can read it you should set the approximate
mirage effect before starting the elevation adjustments.

This will improve the chance of a good cold bore shot. If you set all of these factors before
firing the first sight-er(Shooting target matches) it will minimize the sight correction needed.

Spin drift is just like the Coriolis effect it does not make much difference at 400 or 500 yards
but at 1000+ it starts having an effect on the bullet that can spoil a shot.

To me Coriolis is the tough one to figure out because it is also affected by the direction that the
shot is fired compared to the rotation of the earth.

Good Thread !!!!!!!

J E CUSTOM
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Last edited by J E Custom; 01-23-2011 at 12:07 AM.
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  #16  
Old 01-23-2011, 01:36 AM
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Re: SPIN DRIFT!....I'm such a dummy

Quote:
Originally Posted by J E Custom View Post

Spin drift is just like the Coriolis effect it does not make much difference at 400 or 500 yards
but at 1000+ it starts having an effect on the bullet that can spoil a shot.

To me Coriolis is the tough one to figure out because it is also affected by the direction that the
shot is fired compared to the rotation of the earth.

Good Thread !!!!!!!

J E CUSTOM
Coriolus has less to do with the direction of fire and more to do with which hemisphere you are in and how far or close you are to the equator. The vertical component has a fair bit to do with your direction of fire. The horizontal component has to do with how close you are to which pole. Northern hemisphere shooters will see right hand impacts and SH shooters will see left hand impacts which out to 1K is minimized from using a right hand twist barrel. In the NH, we see coriolus AND spin drift combined.

Too bad someone reputable doesnt produce a left hand twist barrel for us NH shooters.

One of the best animations illustrating the right hand NH impact vs left hand SH impact is below:

http://www.youtube.com/watch?feature...&v=__SlJtnpCD8

http://www.youtube.com/watch?feature...&v=mcPs_OdQOYU
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Last edited by Michael Eichele; 01-23-2011 at 02:36 AM.
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  #17  
Old 01-23-2011, 09:39 AM
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Re: SPIN DRIFT!....I'm such a dummy

Quote:
Originally Posted by Michael Eichele View Post
Coriolus has less to do with the direction of fire and more to do with which hemisphere you are in and how far or close you are to the equator. The vertical component has a fair bit to do with your direction of fire. The horizontal component has to do with how close you are to which pole. Northern hemisphere shooters will see right hand impacts and SH shooters will see left hand impacts which out to 1K is minimized from using a right hand twist barrel. In the NH, we see coriolus AND spin drift combined.

Too bad someone reputable doesnt produce a left hand twist barrel for us NH shooters.

One of the best animations illustrating the right hand NH impact vs left hand SH impact is below:

YouTube - EFECTO CORIOLIS

YouTube - coriolis effect (2-11)
Exactly !!!! that's why I said it was difficult to calculate for each shot. Even your explanation sounds
difficult to understand.

And as you know if you fire a projectile along the equator, Coriolis has no effect "BUT"
if you fire it north or south it has the most effect, So each shot is somewhere in between
and must be calculated for that angle to get a correction.

The best description of Coriolis is Leade just like a running target. The problem is in the correct
calculation.

Also the Brits have been using left hand twist a loooong time.

I wonder if they knew something about it back then. They did have a 2000 yard match.

J E CUSTOM
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Last edited by J E Custom; 01-23-2011 at 09:54 AM.
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  #18  
Old 01-23-2011, 09:44 AM
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Re: SPIN DRIFT!....I'm such a dummy

A little funny story--

I was out antelope hunting last year and had the amount of spin drift on my drop chart. I was bored sitting there and got to looking at the drop chart and suddenly realized I could not remember whether spin drift was left or right.
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  #19  
Old 01-23-2011, 01:21 PM
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Re: SPIN DRIFT!....I'm such a dummy

Thanks for posting thses links. Very useful addition to Bryan Litz' book.

Bob

Quote:
Originally Posted by Michael Eichele View Post
Coriolus has less to do with the direction of fire and more to do with which hemisphere you are in and how far or close you are to the equator. The vertical component has a fair bit to do with your direction of fire. The horizontal component has to do with how close you are to which pole. Northern hemisphere shooters will see right hand impacts and SH shooters will see left hand impacts which out to 1K is minimized from using a right hand twist barrel. In the NH, we see coriolus AND spin drift combined.

Too bad someone reputable doesnt produce a left hand twist barrel for us NH shooters.

One of the best animations illustrating the right hand NH impact vs left hand SH impact is below:

YouTube - EFECTO CORIOLIS

YouTube - coriolis effect (2-11)
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  #20  
Old 01-23-2011, 02:40 PM
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Re: SPIN DRIFT!....I'm such a dummy

JE,

I wasnt trying to undermine anybodies abilities or intelegence. Im sorry if I came accross that way.

I guess what I was trying to get at was that right coriolus shouldnt be difficult to figure out. To the best of my knowledge, the left or right hand impact are very consistent regardless of direction of fire. Once you figure out how much, you can use that value regardless. Now if we are talking a due east or due west shot, then there is a vertical component which I understand to be very minimal. I also believe that the closer you are to the poles, the greater the effect. Again, regardless of the direction of fire.

I may be wrong about this who knows? Maybe someone who really knows their physics can chime in. Maybe I will learn something.

Now if we could just get an AMERICAN barrel maker to make left hand twists.............

M
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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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  #21  
Old 01-23-2011, 11:53 PM
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Re: SPIN DRIFT!....I'm such a dummy

Quote:
Originally Posted by Michael Eichele View Post
JE,

I wasnt trying to undermine anybodies abilities or intelegence. Im sorry if I came accross that way.

I guess what I was trying to get at was that right coriolus shouldnt be difficult to figure out. To the best of my knowledge, the left or right hand impact are very consistent regardless of direction of fire. Once you figure out how much, you can use that value regardless. Now if we are talking a due east or due west shot, then there is a vertical component which I understand to be very minimal. I also believe that the closer you are to the poles, the greater the effect. Again, regardless of the direction of fire.

I may be wrong about this who knows? Maybe someone who really knows their physics can chime in. Maybe I will learn something.

Now if we could just get an AMERICAN barrel maker to make left hand twists.............

M
Thanks :but I wasn't offended . It is a discussion and open for comments and the more
we get hopefully the more we learn.

There are a lot of things that I am not an expert about and this is one of them. I do know
that you almost have to have a computer to figure coriolus effect.

I have heard the theory behind having a right hand twist is to prevents the barrel from
trying to unscrew upon firing.

I have not seen this happen to a left hand twist barrel but if anyone has please comment.

J E CUSTOM
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Last edited by J E Custom; 01-24-2011 at 08:09 AM.
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