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# 9 o'clock vs. 3 o'clock wind drifts different with same wind velocity???

#15
02-12-2012, 08:56 AM
 Junior Member Join Date: Oct 2011 Posts: 12
Re: 9 o'clock vs. 3 o'clock wind drifts different with same wind velocity???

caveat: i am green on this subject so i ask you to wait for others to support or deny my notions below.

this was an interesting enough topic that i felt compelled to contribute in an anecdotal way.

often using extremes in the case of variables helps one understand what roll the variable may have in the big picture. having said that, i can understand that an object spinning into another has the propensity to ride up it; pushes the other object down and it goes up from this "collision". friction and what i will call inertia (might not be correct) seem to contribute the most to how an object spinning will react within its environment. air being less dense(low friction?) than the mediums i conjure up in my mind i understand these effects will be much less vivid but none the less apparent especially when taken to an extreme; e.g. the 1000 yards in this discussion.

i can also see how an object contacting a spinning object the way it spins would tend push it down.

if i had to take a scientific guess i would extrapolate that the air contacting the spinning bullets caused localized areas of high pressure in the lower quadrants vs. the upper yielding a kind of buffer to the effects of gravity.
i made a crude drawing to possible explain what i think maybe happening.

i look forward to more input on this matter.
#16
02-12-2012, 11:01 AM
 Silver Member Join Date: Jul 2010 Posts: 420
Re: 9 o'clock vs. 3 o'clock wind drifts different with same wind velocity???

Sounds a lot like a dialing concern to me. Going back and forth over Zero? 1 minute + or - and spin drift only leaves a few inches which is within reason of wind differences!
#17
02-12-2012, 03:19 PM
 Gold Member Join Date: Jan 2011 Posts: 600
Re: 9 o'clock vs. 3 o'clock wind drifts different with same wind velocity???

Ok so we've explained the difference in 3 o'clock vs. 9 o'clock under same velocity winds.

Next question?

According to my ballistic program Bulletflight there is no vertical POI change from no wind, 3 o'clock, or 9 o'clock even when I go from a 0 mph to 20 mph? That contradicts the wind charts shown earlier in this thread. I made sure SD & CE were being accounted for, however I also ran it with SD & CE off and still no change in vertical POI?
#18
02-12-2012, 03:43 PM
 Platinum Member Join Date: Oct 2009 Location: Thunder Basin, WY Posts: 1,788
Re: 9 o'clock vs. 3 o'clock wind drifts different with same wind velocity???

Quote:
 Originally Posted by shortpants Ok so we've explained the difference in 3 o'clock vs. 9 o'clock under same velocity winds. Next question? According to my ballistic program Bulletflight there is no vertical POI change from no wind, 3 o'clock, or 9 o'clock even when I go from a 0 mph to 20 mph? That contradicts the wind charts shown earlier in this thread. I made sure SD & CE were being accounted for, however I also ran it with SD & CE off and still no change in vertical POI?
That was my original question also, back when I started the linked thread (Wind Direction Changes our Vertical Impact- Fact or Myth?). My programs don't show any vertical difference due to any amount of wind either. However, I seem to maybe have seen it, and aparantly others have too. Brian Litz (Ballistic Expert at Berger) says it happens.

Really not trying to hyjack your thread, just thought it was relevant since we're discussing spin drift. Hell, used to be that alot of people didn't even believe in spin drift........some still don't. Some say it has no effect until we're beyond 1000 yds, others say they begin seeing it at 500 yds.??
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SBruce

#19
02-12-2012, 04:58 PM
 Gold Member Join Date: Jan 2011 Posts: 600
Re: 9 o'clock vs. 3 o'clock wind drifts different with same wind velocity???

Your not hi-jacking you are contributing!

Most people don't shoot past 500yds. and most of those that do most likely are lucky to hold MOA. The effects of SD @ 500yds are closer to .25MOA. that is why a small percentage of shooters understand this science. I am trying. I first have to understand the logic and then attempt to learn to apply it.

Thanks for your thoughts SBRUCE!
#20
02-12-2012, 05:21 PM
 Platinum Member Join Date: Oct 2009 Location: Thunder Basin, WY Posts: 1,788
Re: 9 o'clock vs. 3 o'clock wind drifts different with same wind velocity???

Quote:
 Originally Posted by shortpants Your not hi-jacking you are contributing! Most people don't shoot past 500yds. and most of those that do most likely are lucky to hold MOA. The effects of SD @ 500yds are closer to .25MOA. that is why a small percentage of shooters understand this science. I am trying. I first have to understand the logic and then attempt to learn to apply it. Thanks for your thoughts SBRUCE!
You're welcome. Glad I could contribute.

I am with you, still trying get all the theory worked out in my head too, so when something wierd happens on the 1000 yd range at least I have some possible explanations in mind.
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Aim small = Miss small
SBruce

#21
02-12-2012, 05:36 PM
 Platinum Member Join Date: Nov 2008 Posts: 1,047
Re: 9 o'clock vs. 3 o'clock wind drifts different with same wind velocity???

A couple of handy links that may help explain the subject.

Spin and Coriolis Drift

External ballistics - Wikipedia, the free encyclopedia

AS for the vertical drift due to wind direction. I don't think wind from any direction is ever completely horizontal over the fight of a bullet that travels a long distance. As such there will always be a vertical wind component and that is the main reason why shots will go high or low.
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