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.
spindrift.png



i look forward to more input on this matter.
 
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!
 
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?
 
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.??
 
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!
 
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.
 
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.
 
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.

Thanks for the links Top Shot.

If I'm understanding your response on vertical drift your saying vertical POI changes are caused by vertical winds and not a factor of spin drift. That is what I was saying but contradicts the charts shared earlier. I am only sharing what my calculator is showing. Someone with real world expertise would be of great assistance on this subject.
 
Thanks for the links Top Shot.

If I'm understanding your response on vertical drift your saying vertical POI changes are caused by vertical winds and not a factor of spin drift. That is what I was saying but contradicts the charts shared earlier. I am only sharing what my calculator is showing. Someone with real world expertise would be of great assistance on this subject.

There could be a small amount of bullet deflection in the up and down direction due to spin/wind interaction. After all, a spinning object will deflect at right angles to the external force being applied to its side. The magnitude of this deflection is debatable.

Given that a bullet will yaw into the wind to stay nose first. There is not going to be much of a surface area that is exposed to side wind. Drag then pulls the bullet in the direction that the wind is blowing.
I still think the vast majority of vertical deflection is due to the wind direction not being perfectly horizontal in the real world. After all, the wind has to flow over hills and valleys etc. The ground is never perfectly flat and trees and land features can create a swirling effect. One of my favourite long range shooting areas has a tree line along one side. This always results in the bullet hitting low on the target as the wind comes in over the trees and then drops down to a lower level. With the wind coming from the right, spin theory suggests that the bullet should hit high but it doesn't due to the local environment.
 
Assuming that the wind is moving perfectly horizontal in relation to the bullet, bullets WILL have a vertical compnent versus a no wind condition. They will impact higher with winds from 3Oclock and lower when from 9Oclock. Assuming that this is a right twist rifle. The opposite is true of a left twist barrel. It is a simple nose slightly up versus nose slightly down when compared to the nose position of the bullet in a no wind condition.

Your program does not show this because it does not have that capablity. Most programs dont show you the vertical changes due to head or tailwinds either. I have never spent the time to include the vertical component from crosswinds in any of my software, however I have integrated the vertical component from the head/tail wind into all of my software as well as spin drift.

M
 
Interesting Michael because I tested the theory that this program might not be capable of calculating vertical changes in relation to wind. At first glance I thought it did indeed calculate it but after reading your post I believe the change in vertical impact was due to the bullet losing more velocity in a head wind vs no wind. The changes were minimal, in fact I had to give it a 20mph headwind to change the POI 2-3".

So the lesson here is my program and several others are not capable of accounting for the vertical effects created by spin drift.

That being said would you say using the 3 to 1 ratio (3 moa of SD = 1 moa vertical change in POI). This is an exaggerated example.
 
The Charts posted that Speedy did are accurate--have used them for years. Vertical is a whole different animal---many reasons we get vertical. This is from Speedy and will help give you a better understanding of the conditions that contribute to vertical. One thing that he does not expand on is velocity deviation which in my game of 1k BR is HUGE oh btw did I say HUGE!

Tips on Vertical Problems


1. A lot of rifles are muzzle heavy. Some rifles have too heavy a barrel and this causes vertical problems, especially those who shoot free recoil

2. Firing pin coming out of hole in bolt in the cocked position. This will cause poor ignition. Take bolt out of rifle and look in firing pin hole. If you cannot see entire end of firing pin it has come out of the hole.

3. Firing pin dragging in bolt or shroud. Listen to the sound when you dry fire. If not the same sound each shot something is wrong.

4. Trigger sear too much spring. Hold trigger in firing position and push down on sear with your thumb. If it is hard to push down, this will cause vertical problems.

5. Firing pin spring too weak or too strong will cause vertical problems. If you think this is the problem change springs and see what happens.

6. Tightening front sand bag too tight on stock. When you try to pull rifle back by hand and rifle feels like it is stuck in the bag it is too tight. Rifle should move in sand bags evenly, not jerk or chatter when pulling back by hand.

7. Action not level with top of stock running down at muzzle end. Rifle will recoil up at butt end causing vertical.

8. The load that are shooting can too light or heavy and can cause vertical problems.

9. Bench technique not same every shot. One example, should against stock one shot and not the next.

10. Bad primers – if getting vertical try other primers.

11. Bad scope, if scope is bad from shooting vertical, if you change your load in anyway and vertical goes away it is not your scope.

12. Rifle not balanced, it does not recoil right, jumps in bag. If rifle is built properly this will not happen.

13. Some stocks are very flexible. This can cause vertical.

14. Front sandbag too hard. I personally have never had a rifle that will shoot consistent with a rock hard front sandbag. It always causes vertical or other unexplained shots.



Other Tips:

1. Head on front rest loose. A lot of rests have movement even when you tighten them as much as you can. This can cause unexplained shots.

2. Some 30 mm scope rings are not getting tight enough to hold scope. Scope slipping in rings under recoil. This will cause point of aim movement.

3. Keep shell holders clean, in press and priming tool. I have seen so much dirt in shell holders that cases are sized crocked on body. Also primers cutting primer pockets bigger shaving brass as you seat the primer.

4. Whenever you can, set up so you can load watching conditions on the range as you load your ammo. That way you will be aware of any changes in conditions since your last group and you will be mentally prepared for the new condition.

5. Learn to look at whole field of flags, not just the row in front of you. A lot of times conditions change away from you will cause shot to go out of group before change in condition shows up in front of your bench.

6. When you chamfer the inside of your case necks make sure they are smooth enough that they don't peel jacket material off when you seat the bullet.

7. I see people walking around with case necks turned up in the loading block. A lot of the time there is condensation dropping from the roof of your loading area. If one drop of water gets in case you are in trouble on the shot. How many times have you had a bad low shot when it has been raining and you have been walking around with your cases turned up in your block?

8. Learn to keep head down and follow through when you are shooting each shot.

9. I hear a lot of discussion about low shots in a group and apparently this occurs a lot on the fifth shot. If it is your 5th shot most of the time you can bet you are doing something at the bench.

10. If 5th shot is a problem, which everyone does at times, we do what I call wishing the last shot in. We just aim, pull the trigger, and do not worry about the wind flags.

11. This year alone I have seen nine lock rings on scopes that are not tight. Guess what that does to your group? Make sure yours are tight.

12. When you realize that the wind is your friend you will become a much better benchrest shooter.

13. Practice in wind, not in good condition.

14. Pay attention to angle changes on flags. Even though you see the same color angle changes make a big difference in your groups.

15. The longer you wait between shots when a condition is changing the more the condition change will affect your bullet.

16. If you do not know how to read wind flags or have never seen a wind flag try to shoot your group with the flags all going in one direction.

17. Equipment at bench has to work flawlessly. If it doesn't get it fixed or get rid of it. We need all our attention on wind flags.

18. Learn to shoot with both eyes open so you can see more of the conditions.

19. Free recoil shooters should be sure rifle hits shoulder squarely on recoil, not on edge of shoulder or muscle of arm.

20. Should have your own stool to sit on so that you can sit at the bench comfortably for you.

21. Hunting rifle barrels – do not get cleaned enough. If you keep barrel clean it will shoot better for you. You should clean barrel good after every 10 to 12 shots.

22. Most hunting rifles will not put first shot after cleaning with rest of shots. So after cleaning if you have a rifle that won't group first shot shoot one fouling shot before going hunting or before you shoot for group size.

23. When working up a load for your hunting rifle take your time and do not let the barrel get hot on you.
 
Thanks Boss Hoss, you've shared these tips and several other links regarding wind in the past. I read them all but as you can see it has not sunk in yet. Trying to teach me something new is like trying to find a cure for cancer. The cure is coming eventually but we got a long way to go. The more I read and shoot the more I learn.
 
Another interesting fact is that 52" of drift @ 5mph becomes 94" when 10mph is plugged in. I would think it would be 104". Ive gone through this app and can't find what could be causing these readings. If I take spin drift off and coriolis off then the drift is the same whether it be a 3 o'clock or a 9 o'clock. It does make sense that with a no wind hold the bullet would drift right (and low) with a right hand twist so I could understand a different hold when dealing with a 90* or a 270* wind. I just have a hard time believing it would be as great as what it is telling me.

Revisiting this question it all makes since now. The 52" of drift is actually 42" of wind drift and 10" of SD with a 9 o'clock wind at 5mph. Double the wind to 10mph and the wind drift doubles to 84" + 10" of SD= 94".

Still a long way from curing cancer but we have disproven the theory that it is impossible to teach me something!
 
Warning! This thread is more than 13 years ago old.
It's likely that no further discussion is required, in which case we recommend starting a new thread. If however you feel your response is required you can still do so.
Top