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Spin Drift and Acceleration

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  #1  
Unread 01-07-2013, 03:40 PM
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Spin Drift and Acceleration

I shot a doe this past week at a pretty good distance for Mississippi. 428 yards. 168 VLD worked well and the elevation was spot on. 7MOA and I was dead center. The problem was that I was off to the right a few inches. There was absolutely zero wind so other than shooter error I was wondering how much spindrift could I count on. Ballistic AE on the iphone said about 1.25 inches.

What do yall use to calculate drift and acceleration. I was about 4-5 inches too far right and I know not all of that is due to the above but wanted to see how the brain trust manages that.
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  •   #2  
    Unread 01-07-2013, 03:50 PM
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    Re: Spin Drift and Acceleration

    Spin drift at that distance is not going to be much at all maybe 1/4"-1/2" if that much. If it wasn't shooter error, then what I would be looking at is if your scope is mounted level. I would also go out to the range and see where it shoots at 400 yds.
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      #3  
    Unread 01-07-2013, 03:54 PM
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    Re: Spin Drift and Acceleration

    1 1/4" of SD, the accuracy of the rifle ?? Lets guess 3/4 moa so there is another 3.3" at 428 yards. that is a total of over 4 1/2".

    Jeff
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      #4  
    Unread 01-07-2013, 04:00 PM
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    Re: Spin Drift and Acceleration

    Broz, are you saying there is 1.25" of spin drift at roughly 400 yards?
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      #5  
    Unread 01-07-2013, 04:03 PM
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    Re: Spin Drift and Acceleration

    Quote:
    Originally Posted by Korhil78 View Post
    Broz, are you saying there is 1.25" of spin drift at roughly 400 yards?
    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
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      #6  
    Unread 01-07-2013, 04:05 PM
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    Re: Spin Drift and Acceleration

    Oh ok...I was scratching my head trying to figure out how I was figuring it wrong! haha
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      #7  
    Unread 01-07-2013, 04:19 PM
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    Re: Spin Drift and Acceleration

    Quote:
    Originally Posted by Korhil78 View Post
    Broz, are you saying there is 1.25" of spin drift at roughly 400 yards?
    you can get that, depends on your bore dia, twist rate and MV
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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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