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Spin Drift and Acceleration

 
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  #8  
Old 01-07-2013, 04:26 PM
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Re: Spin Drift and Acceleration

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Originally Posted by Broz View Post
That was the OP's number. My 300 win shows less at .1 moa which is closer to 1/2 inch. But I don't have all his ballistics so I went with his number from his program. A pretty good rule of thumb is 5" or 1/2 moa at 1000. So an inch at 428 is not way out there.

One other comment. I have never seen it where there was "NO wind" somewhere during the shot. That sure could be but it would be very rare.


Jeff
When ever I see that I think, very little so it was ignored. I think folks forget that a 2mph wind at 400yrds will drift your bullet 2" or more
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Keep in mind the animals we shoot for food and display are not bullet proof. Contrary to popular belief, they bleed and die just like they did a hundred years ago. Being competent with a given rifle is far more important than impressive ballistics and poor shootability. High velocity misses never put a steak in the freezer.

Joe
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Old 01-07-2013, 04:28 PM
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Re: Spin Drift and Acceleration

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Originally Posted by Joe King View Post
When ever I see that I think, very little so it was ignored. I think folks forget that a 2mph wind at 400yrds will drift your bullet 2" or more
And a 1/2 to 3/4 MPH wind is hard to detect on your face.

Jeff
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  #10  
Old 01-07-2013, 04:36 PM
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Re: Spin Drift and Acceleration

So very true with the wind. The Mississippi delta is flat. Very flat but occasionally the wind settles. What wind there was that day was coming from the 7oclock. Could have been a few MPH in there. Usually are.

The app I used was the Ballistic AE app for the iphone. It shows 1.53"@425

Gun is a GAP 280AI with 168vld at 2800fps. 1/8 twist. 7"Dixie Precision Rifle Suppressor

I didn't think about the scope base. I have Kelby two piece dove tail bases and rings. I don't recall the gun and scope being out of line when shooting it. Perhaps I'll practice more and get a one piece base
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  #11  
Old 01-07-2013, 04:51 PM
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Re: Spin Drift and Acceleration

Did you dial in the shot?

Are you using a scope level and have you trued your reticle to bullet path?

Jeff
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Old 01-07-2013, 04:57 PM
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Re: Spin Drift and Acceleration

As stated he didn't give any specifics on ballistics I ran numbers for my 7mag came up with 5.8 moa up and .1moa of drift = 0 clicks.
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  #13  
Old 01-07-2013, 06:41 PM
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Re: Spin Drift and Acceleration

Spin and Coriolis Drift

11.5" at 1000 is more than I expected. Not sure what caliber, MV ect. I dialed up 7MOA for my shot and held middle of the shoulder. Not much wind from 7oclock. I'm ok with shooter error if that is what it is. It seems the consensus is that 1-2 clicks a most for drift.
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  #14  
Old 01-07-2013, 06:46 PM
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Re: Spin Drift and Acceleration

So do you have a level to eliminate cant? If not that would be high on the possibility list.

Also, I am not comfortable with the 11.5" at 1000. I would be looking for data input error there. That is to much. I don't even use coriolis till beyond 1200 as it is such a small correction. And I have never seen much more than 1/2 moa for SD at 1000 in many rifle tested.

Jeff
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