Advanced Marksmanship Crosswind Effects on DOPE Elevation at Long Ranges

[riffraff]

Experienced shooters -

I am an intermediate-level shooter....past experience out to 800 yards. I now have an 1200 yard range available, and a new rifle/ammo load and decent DOPE to do it (.260Rem, 139gr Lapua at 2820fps muzzle velocity).

A few days ago I was reading a thread about crosswind effects....that a right wind will spin the bullet high (with a right-twist barrel), and a left wind will spin the bullet low.....effects similar to 'Spin Drift'.

I realize that each rifle/bullet combination will be a bit different, and that I will have to develop my own DOPE for my gear. But I am looking for an estimate of how much adjustment or holdover is required....are we talking 2" at a thousand yards, or 10 or 15 inches for a 10mph crosswind? Or is the effect insignificant for tactical match-sized targets?

Does anyone have a 'rule of thumb' or some actual DOPE from their gear at 800, 1000, or 1200 yards to get me started?

Any help would be appreciated.

Buzz

 

[NevadaZielmeister]

Experienced shooters -

I am an intermediate-level shooter....past experience out to 800 yards. I now have an 1200 yard range available, and a new rifle/ammo load and decent DOPE to do it (.260Rem, 139gr Lapua at 2820fps muzzle velocity).

A few days ago I was reading a thread about crosswind effects....that a right wind will spin the bullet high (with a right-twist barrel), and a left wind will spin the bullet low.....effects similar to 'Spin Drift'.

I realize that each rifle/bullet combination will be a bit different, and that I will have to develop my own DOPE for my gear. But I am looking for an estimate of how much adjustment or holdover is required....are we talking 2" at a thousand yards, or 10 or 15 inches for a 10mph crosswind? Or is the effect insignificant for tactical match-sized targets?

Does anyone have a 'rule of thumb' or some actual DOPE from their gear at 800, 1000, or 1200 yards to get me started?

Any help would be appreciated.

Buzz

Buzz,

My personal experience at shooting long range out to 800 meters does not provide any change in elevation due to crosswind. I suspect that maybe the range and topography of the land may be pushing your bullet different that what is normal. Whenever I miss at that kind of range, the spread is side to side and never up and down. Maybe I am wrong, but I cannot see how a bullet would increase or decrease by overcoming the effects of gravity just from a wind of any kind. Remember, the greatest force acting on the bullet in flight is gravity. It is MUCH greater than wind effects. Maybe some thoughts: Is the range flat? Are there berms or trees near the bullets path of flight? Could you be altering your shooting due to the greater distance? Maybe the function of the rifle is coming into play?

I am curious to see if anyone else has personal experience, since mine indicates no change to the elevation of the bullet due to crosswind.

 

[Cordova13]

I don't have any personal experience but Ive watched the sniper 101 videos on youtube from tiborasaurusrex. On his spin drift video he talks says that a right wind and a right twist barrel will put pressure on top of the bullet causing the bullet to fly in more in the direction its going instead of being angled up which will make it fly better and make it go farther. A left wind will do the opposite and put pressure on the bottom of the bullet. I think it is so little of an effect to where you wouldn't have to correct for it if any correction at all.

Again I don't know if this happens since Ive never experienced it but the guy seems to be pretty good at shooting..

 

[Notso]

This is purely thinking out loud on my part here, so take it with a grain of salt - as I'm no ballistics expert. However, I did stay in a Holiday Inn recently.

But just applying common sense physics, I can't see how the effect of wind doesn't have an effect on the bullet drop. Ignore spin drift for a moment. If a bullet is shot in absolutely zero wind, then it has a ballistic trajectory to the target with a specific amount if elevation needed to hit the target for a given range, MV, bullet BC, density alt, etc. etc. Assuming all other things are equal, but you add in a 20 mph pure left to right crosswind - you will now either need to hold or dial for that crosswind. So you would effectively be pointing the barrel left of the target by some amount. Now the bullet is not only traveling in a pure vertical ballistic arc, but a curvilinear arc as well with a horizontal component as the wind "pushes" the bullet back towards the target. Think of the golf ball protracer graphic they use on TV to show the ball flight - its exactly like that.

So the point being is the bullet has to travel a longer path to get to the target, so I would therefore think it would hit lower in all cases than in a no wind condition - with the amount lower relative to the amount of crosswind. Because if the bullet starts with the same amount of energy leaving the muzzle, but has to travel a further distance to get to the same point, then it would be in a lower energy state when it arrived there. So therefore it would have to hit lower once it got there.

Does this make sense?

 

[Sterling Shooter]

Most all of my LR experience is in NRA LR Competition; and, from that perspective, I have not felt a need to explore this topic since my appraisal of average wind from muzzle to target is not likely to be exact enough, or my hold exact enough that I could discern any other physical effect upon the bullet not already known for sure to be important to good shooting.

 

[Greg Langelius *]

External Ballistics

Excerpt describing Magnus effect:

Spin stabilized projectiles are affected by the Magnus effect, whereby the spin of the bullet creates a force acting either up or down, perpendicular to the sideways vector of the wind. In the simple case of horizontal wind, and a right hand (clockwise) direction of rotation, the Magnus effect induced pressure differences around the bullet cause a downward (wind from the right) or upward (wind from the left) force viewed from the point of firing to act on the projectile, affecting its point of impact. The vertical deflection value tends to be small in comparison with the horizontal wind induced deflection component, but it may nevertheless be significant in winds that exceed 4 m/s (14.4 km/h or 9 mph).

Magnus effect and bullet stability

The Magnus effect has a significant role in bullet stability because the Magnus force does not act upon the bullet's center of gravity, but the center of pressure affecting the yaw of the bullet. The Magnus effect will act as a destabilizing force on any bullet with a center of pressure located ahead of the center of gravity, while conversely acting as a stabilizing force on any bullet with the center of pressure located behind the center of gravity. The location of the center of pressure depends on the flow field structure, in other words, depending on whether the bullet is in supersonic, transonic or subsonic flight. What this means in practice depends on the shape and other attributes of the bullet, in any case the Magnus force greatly affects stability because it tries to "twist" the bullet along its flight path.

Paradoxically, very-low-drag bullets due to their length have a tendency to exhibit greater Magnus destabilizing errors because they have a greater surface area to present to the oncoming air they are travelling through, thereby reducing their aerodynamic efficiency. This subtle effect is one of the reasons why a calculated Cd or BC based on shape and sectional density is of limited use.

I never go shooting with the intention of firing only one round. Therefore, my LR zero gets refined by using sighting shots; so any horizontal and/or vertical deviation is compensated.

My personal "takeaway" regarding Magnus Effect is that crosswinds do more than simply causing horizontal deflection. They likewise increase dispersion, and shift the center of dispersion upward or downward depending on wind direction and magnitude as well as BC; being that higher BC works in favor of increasing this instability factor, accentuating dispersion as crosswind force and BC increase.

This is a strong supporting argument for why a minimum rifling twist aids accuracy.

While the actual vertical deflections of Magnus Effect may be small, its effect on stability can provide insight into why some tendencies, like improved accuracy from reduced rifling twist, can make sense even if a simple explanation proves elusive.

Understand that BC values have meaning only when the bullet does not yaw (or pitch), and degrade immediately upon any manifestation of such yaw (or pitch). This adds a completely separate and additional drop component to any true trajectory path whenever any sort of instability is present.

People make assertive statements regarding stability and "going to sleep", concluding that no other force can be present to increase or decrease stability. Such a force actually is present and frequently so, in the form of Magnus Effect. While the concept of probability makes it a possibility that such forces could be helpful to accuracy, the preponderance of likelihood is that such improvement will be very fleeting, and the great bulk of effects will favor more, rather than less, dispersion.

Accuracy/dispersion is the consequence of a potpourri of forces, large and small. One may attack this admixture by means of equipment upgrades, ammunition refinements, and elegant techniques; but in so doing, one may still only address a portion of a very complex equation. As a consequence, accuracy will vary constantly, and computational efforts will only render approximate results.

For my part, I choose not to swim hard against the swiftest currents, but rather to yield some of any anticipated gain in return for some considerable simplification of the effort expended. This is the basis of my insistence upon seeking adequate, rather than ultimate, accuracy goals.

Greg

 

[Cordova13]

External Ballistics

Excerpt describing Magnus effect:



View attachment 26383

I never go shooting with the intention of firing only one round. Therefore, my LR zero gets refined by using sighting shots; so any horizontal and/or vertical deviation is compensated.

My personal "takeaway" regarding Magnus Effect is that crosswinds do more than simply causing horizontal deflection. They likewise increase dispersion, and shift the center of dispersion upward or downward depending on wind direction and magnitude as well as BC; being that higher BC works in favor of increasing this instability factor, accentuating dispersion as crosswind force and BC increase.

This is a strong supporting argument for why a minimum rifling twist aids accuracy.

While the actual vertical deflections of Magnus Effect may be small, its effect on stability can provide insight into why some tendencies, like improved accuracy from reduced rifling twist, can make sense even if a simple explanation proves elusive.

Understand that BC values have meaning only when the bullet does not yaw (or pitch), and degrade immediately upon any manifestation of such yaw (or pitch). This adds a completely separate and additional drop component to any true trajectory path whenever any sort of instability is present.

People make assertive statements regarding stability and "going to sleep", concluding that no other force can be present to increase or decrease stability. Such a force actually is present and frequently so, in the form of Magnus Effect. While the concept of probability makes it a possibility that such forces could be helpful to accuracy, the preponderance of likelihood is that such improvement will be very fleeting, and the great bulk of effects will favor more, rather than less, dispersion.

Accuracy/dispersion is the consequence of a potpourri of forces, large and small. One may attack this admixture by means of equipment upgrades, ammunition refinements, and elegant techniques; but in so doing, one may still only address a portion of a very complex equation. As a consequence, accuracy will vary constantly, and computational efforts will only render approximate results.

For my part, I choose not to swim hard against the swiftest currents, but rather to yield some of any anticipated gain in return for some considerable simplification of the effort expended. This is the basis of my insistence upon seeking adequate, rather than ultimate, accuracy goals.

Greg

This is what I was trying to explain. You just did it a lot better than me and actually knew what you talking about.
How much vertical effect would it have on a bullet?

 

[Greg Langelius *]

The effect is generally a product of intermediate winds along the trajectory. Honestly, I can't say with any certainty what they are or will be, it's essentially indeterminate. Likewise, the best I can say about those winds' effects is that they will also be indeterminate.

This is sort of like what a spotter is doing when they say to favor right, or up, or left, etc. You can advise that an effect will likely happen and suggest a direction, but how much is a guess.

I once did deliberate testing with a .222 at 300yd, probably over twenty years ago, now. I performed the test by shooting consecutively through a series of wind gusts, while determinedly avoiding any compensation for that wind. I will say that there was some up and down deflection due to crosswinds, and that it was observable at 300yd. I'd say the overall vertical displacement was about 1" to 2", and would not have been observable at all without the aid of an extremely accurate rifle. But understand the effect was slight and only just barely observable. The basic plot of Magnus Effect tends to be a very shallow sine wave, exaggerated horizontally, and greatly diminished vertically.

I would not attempt to quantify these effects, and would strongly advise against trying because intermediate wind is only sometimes, and partially, observable, as well as hard to quantify. Keep in mind that intermediate crosswinds can come simultaneously from opposite directions, with some cancelling within the overall effects.

The best I can suggest is that this comes under the heading of getting to know your rifle and its performance under the broadest range of conditions. I believe that's the closest approximation you can find, and it is going to be dependent on both you and your rifle's unique capabilities.

As I suggested above, the best we can derive is approximations. Magnus Effect is a small deviation, and can very easily get completely lost in the chorus of larger effects.

Greg

 

[riffraff]

Thanks for all the good answers, guys.....I will file this one in the category of "Don't worry, it will be lost in the 'noise'...just go shoot".

 

[damoncali]

Thanks for all the good answers, guys.....I will file this one in the category of "Don't worry, it will be lost in the 'noise'...just go shoot".

Except it won't. It's a real effect, that, although hard to see, is significant. You can figure on the wind blowing your bullets at about a 20 degree angle up or down, and not just side to side. There are three reasons people don't notice it, all related to people just not believing what they see in favor of what seems like a more logical reason.

1) Most people aren't aware that it happens and will just assume they pulled the shot low or high. So it takes a pretty sizable misread of the wind combined with a very confident call to notice. Most are so pissed that they missed the wind that they don't so much notice that they *didn't* miss the elevation hold. It's easy to blame yourself when you don't deserve it.

2) if there's a constant wind and you zero your windage and you find you need to come up or down a click or two, it's tempting to assume that your elevation windage was just a little off for some reason. Maybe the target isn't quite at the range you thought, maybe the velocity is off. Maybe this maybe that. But in reality, a side wind blows your bullets sideways and up/down.

3) People want to blame vertical wind more than it deserves to be blamed. Because what else could it be?

It's an effect called aerodynamic jump (first documented about 100 years ago, although seldom written about outside of engineering literature), and is a key ballistics concept that is at the heart of rifle accuracy. A large part of bullet dispersion (that is not shooter or wind induced) is also attributable to aerodynamic jump, which has causes other than wind. It's real, and it's a big part of what we deal with as shooters whether we see it or not.

 

[riffraff]

damon -

Sounds good, do you have a formula, or a specific DOPE entry at 800, 1000, or 1200 yards that would be good as a starting point?

Thanks,

Buzz

 

[damoncali]

The math is on the complicated side, and depends on the twist rate (and direction) and some hard to get bullet characteristics. A decent swag is that the impact will be maybe 1 MOA down for every 4 right (with a right hand twist), and one up for every 4 left. The tough part, as always, is reading the wind and truly knowing your zero at distance. The best way to figure it is to pay attention - especially when you whiff on the wind - and trust your call. Resist the urge to just erase that shot from your mind and look carefully at where it hit.

I can recall vividly one time when I held and called a perfect X at an f class match with a very accurate rifle. The shot was a slightly high 9 to the left (10 o'clock) because I missed the wind shift. I know I held it centered, and I had shot a 199 on the very last string, so I know it wasn't the gun. It would be really easy to have written that elevation off as me, but it's not, it's the wind. Just imagine that it blows not exactly horizontally but at a slight angle.


Edit: Xcount below points out that 1 to 4 is a bad guess at 1000 yards, and he's right. Sorry for reading your question too fast - 1 to 4 is a better swag at short ranges. A better (rough) answer is that the vertical deflection might be in the neighborhood of 1/2 MOA for a stiff cross wind at any range. Up to you to decide how significant that is.

 

[riffraff]

Thanks, Damon!

 

[Xcount]

The math is on the complicated side, and depends on the twist rate (and direction) and some hard to get bullet characteristics. A decent swag is that the impact will be maybe 1 MOA down for every 4 right (with a right hand twist), and one up for every 4 left. The tough part, as always, is reading the wind and truly knowing your zero at distance. The best way to figure it is to pay attention - especially when you whiff on the wind - and trust your call. Resist the urge to just erase that shot from your mind and look carefully at where it hit.

I can recall vividly one time when I held and called a perfect X at an f class match with a very accurate rifle. The shot was a slightly high 9 to the left (10 o'clock) because I missed the wind shift. I know I held it centered, and I had shot a 199 on the very last string, so I know it wasn't the gun. It would be really easy to have written that elevation off as me, but it's not, it's the wind. Just imagine that it blows not exactly horizontally but at a slight angle

i'm gonna raise the bullshit flag on this because there is just too much b.s. on this website that goes uncalled. i've seen too many national champions and done too much shooting myself in 4-13 minutes of wind at 1k to have someone say there is a significant effect on elevation from crosswind. There might be a slight effect, very slight, even in Litz' book he says it is a non factor. Absolutely not 1 moa per 4 moa of wind, absolute b.s. and you will never be able to prove what you said is true. don't give a swag on something and say "the match is complicated". If there is math involved then you can PROVE IT. A person does not have to be a math genius to hold elevation at 1k, you don't need a calculator on the line either.
Some people are probably confusing the verfied fact that a .22lr bullet has elevation effect from crosswind, guess what the .22lr bullet is not a boattail. The boattail minimizes the effect. It's a non factor at 1k, your shooting ability will have a much greater effect.

I'll put my NRA LR High Master card on the line, what have you got to put up?

 

[damoncali]

Settle down. Pick up a a copy of Bob McCoy's book or Harold Vaughn's. Both go through the math in some detail (especially McCoy's) and provide examples. If that's not enough dig up a copy of "Exterior Ballistics" by McShane, Kelley and Reno, which also delves pretty deeply into it. And if you actually read Bryan Litz's book, you'll see that he provides and example where the vertical deflection is almost exactly 1:4 - for a boat-tailed bullet.

I should have been a little more clear that this is an effect that is less visible at very long ranges because it comes about due to a muzzle disturbance. So in that sense you're right - I had glossed over the request for 1000 yard adjustments when I wrote earlier. My bad. They should be quite a bit smaller at that range, and I edited my older post to make that more clear.

 

[Spartan67]

After reading this thread, I have a question I would like to add. Would this be a concern when I shoot to 300 yards with a rimfire?


On another note..
Damm!! Im still amazed on all the useful knowledge you can learn here from you guys!!

Thanks!!!

 

[seanhagerty]

Riffraff, you asked for it.

exterior ballistics

 

[damoncali]

It is much more of a concern for people trying to shoot small groups at close range (a few hundred yards) than for people who's primary objective is hitting big targets way out. Benchrest shooters care about it a lot. Again, apologies to all for not making that clear - especially riffraff who asked a specific question and got an answer to a slightly different one because I was reading too fast. At range, most people chalk it up to a minor elevation adjustment without giving it much thought, and that's that. But you can see it if you look carefully - at least you can at 600 yards, which is where I shoot mostly.

At the risk of oversimplifying, the things that impact it are the bullet shape and twist. More twist makes it worse. Very generally, long skinny bullets have a tougher time than short stubby ones, all else equal. The only bullets I've ever seen data for were military rounds (Bob McCoy wrote a paper in the 80's where he calculated the sensitivity of several military 5.56mm rounds to aerodynamic jump -it's on the internet somewhere), so I won't make definitive claims about rimfires, which I don't shoot a whole lot.

 

[Xcount]

Settle down. Pick up a a copy of Bob McCoy's book or Harold Vaughn's. Both go through the math in some detail (especially McCoy's) and provide examples. If that's not enough dig up a copy of "Exterior Ballistics" by McShane, Kelley and Reno, which also delves pretty deeply into it. And if you actually read Bryan Litz's book, you'll see that he provides and example where the vertical deflection is almost exactly 1:4 - for a boat-tailed bullet.

I should have been a little more clear that this is an effect that is less visible at very long ranges because it comes about due to a muzzle disturbance. So in that sense you're right - I had glossed over the request for 1000 yard adjustments when I wrote earlier. My bad. They should be quite a bit smaller at that range, and I edited my older post to make that more clear.

Interesting how you tell me to settle down and to dig into books and then say you were not even talking about the right subject. I guess my HM card is safe. Perhaps i'll just continue to shoot with other high masters and not look in ballistic books for excuses for my bad shots. shooting is about making good shots more than any other factor, all your books and apps and ocw's cannot compensate for making bad shots or bad wind calls. The good news is the fix is more shooting (less reading) and I thought that that is what this is all about, shooting, and being a better shooter.

look at the number of posts in the reloading section or equipment section compared to the posts in the advanced marksmanship section, too much emphasis on equipment and loading (magnus effect, spin drift) when the gross errors come from bad shot technique.

what do I know I don't have 800+ posts here at the hide because i'm too busy shooting matches.

 

[KYpatriot]

Buzz,

Can't leave a former eagle driver hanging, so the equation if you want to build the clock is:

Y = (0.01)(SG) - (0.0024)(L) + 0.032

where:
Y is the vertical deflection in MOA of a 1 mph crosswind
SG is the Gyroscopic stability factor
L is the bullet length in calibers.

and...

SG = (30)(m)/ [(t^2)(d^3)(l)(1+l^2)]

where:
m is bullet mass in grains
t is the rifling twist in calibers per turn (i.e. your rifles twist in inches divided by .264 for your 260Rem)
d is the diameter of the bullet
l is the length of the bullet in calibers

A lapua 139 scenar is about 1.364in in length. If your rifles twist is 1:8, then SG on a standard day at sea level is going to be about 1.7 (there are velocity and atmospheric corrections to the above formula, for clarity I'll skip those...)

So given the above assumptions you'd be looking at about .06MOA per 1 mph, or 0.6MOA per 10mph direct cross. I believe in most tactical shooting you will have far more trouble in windy conditions with horizontal dispersion than vertical until you get really good at wind calling, and that if you are seeing significant vertical it will be due to shooter errors or the velocity ES for the load you are shooting rather than the aerodynamic jump you are questioning.

Why do I say that? Lets assume your rifle has an inherent precision of about 0.75inches at 100yards. Since dispersion depends on TOF and is not linear with distance, we note that the TOF for 2820fps and 100 yards is .109s, and at 1000 yards is 1.499s. So the rifles precision at 1000 will not be ten times worse, it will be almost 14 times (1.499/.109 =13.75) worse, an over ten inch group BEST case before we even get started, meaning every variable is perfectly accounted for with zero shooter error. Now start adding in shooter errors in aiming, trigger control, natural point of aim, scope click consistency, velocity variation, windcalling etc etc and the CEP grows quickly. For example, with your round at 1000 yards a 30fps velocity variation from your calculated dope is about .8 or.9MOA, around 30% more than aerodynamic jump and not at all uncommon. Thats just one thing. So in a sense you were correct it is in the noise. However, it is present and like spin drift can be accounted for. Check and see if your ballistic calculator comps for it, I think the common ones do. Just don't be surprised if you don't see the effect on target because it gets baked in with a lot of other ingredients. The best thing to do is get a range book and shoot, record your holds wind calls and results and look for trends.

Go here to buy Bryan Litz's excellent book and see the discussion/math on this and other external ballistics questions: Applied Ballistics For Long Range Shooting 2nd Edition
vr
SLAK


With respect to the pissing match over theory I'll say this: I have found it true that just because you can do something doesn't mean you understand why it works, and conversely that just because you understand it doesn't mean you can do it. It is obvious that theory without the fundamentals of marksmanship is never going to build a marksman. Yet without theory we would never advance the capability of future marksmen with better rifles, bullets, and ballistic calculators. A shooter that understands the math has no right to resent a marksman that is successful despite having no clue why what he has learned to do by experience works, because that marksman put in the disciplined practice time to hone his skill and deserves the success of that work. I also see no reason that the marksman should resent someone wanting to understand the theory that explains the physics of his skill set knowing that there is no shortcut to success without trigger time. Different things motivate different shooters...for one, getting a hit is reward enough, for others they need to know how it works to enjoy the discipline. Some guys want to tear down and rebuild a better clock, others are content to know what time it is. If we didn't have both types we'd still be using sundials.

 

[sinister]

Topic has been written about before, especially by .22 rimfire benchrest shooters.

Aerodynamic Jump Caused by the Wind

A cross wind will cause the bullet to yaw to the side as soon as it leaves the muzzle - creating aerodynamic jump. However, unlike the jump caused by bullet imbalance, this yaw is predictable since its source is the direction of the wind. Oddly, what happens is that the wind-based aerodynamic jump causes a vertical deflection of the bullet's point of impact. The stronger the wind, the more the vertical deflection will be.

Note that the magnitude of this effect is not small. A .308 168 grain Sierra MatchKing at 2,600 fps will experience a vertical deflection of approximately 3/8" at 100 yards in a 10 mph cross wind. Compare that to the almost 1" of horizontal wind deflection that you might be more familiar with.

Imagine shooting in very gusty winds with a very accurate rifle. You might wind up with a target that looks something like this:

A left to right wind causes bullets to hit low. A right to left wind causes bullets to hit high. (Note that this would be reversed for a rifle with a left hand twist.) So rather than wind causing a pure horizontal dispersion as you might picture, it actually causes a a dispersion at an angle. The faster your rifle's twist, the greater that angle will be.

Now I don't know about you, but it's hard enough for me to keep track of the horizontal impact of the wind without having to worry about a vertical component. The angles of the lines on the figure are drawn to scale for a Sierra 168 grain Match King with a right hand twist at 2,600 fps.

 

[damoncali]

Interesting how you tell me to settle down and to dig into books and then say you were not even talking about the right subject. I guess my HM card is safe. Perhaps i'll just continue to shoot with other high masters and not look in ballistic books for excuses for my bad shots. shooting is about making good shots more than any other factor, all your books and apps and ocw's cannot compensate for making bad shots or bad wind calls. The good news is the fix is more shooting (less reading) and I thought that that is what this is all about, shooting, and being a better shooter.

look at the number of posts in the reloading section or equipment section compared to the posts in the advanced marksmanship section, too much emphasis on equipment and loading (magnus effect, spin drift) when the gross errors come from bad shot technique.

what do I know I don't have 800+ posts here at the hide because i'm too busy shooting matches.

Nobody is arguing with you. I was unclear and you were correct to point that out.

 

[Xcount]

KYPatriot,
I replied to a guy that was blaming high 9 on a crosswind, that's b.s. He had a high 9 because that is where he pointed the rifle. Good on him for realizing he was talking about something else and that crosswind effect is not the big factor he was thinking it was. It's not a pissing contest when someone that knows what he is talking about is trying to teach someone, and that someone acknowledges his mistake.

I find it interesting how many of you guys here love to quote from Litz' book after he specifically states marksmanship is the biggest factor in your rounds hitting where you want them to. Brian is a National Champion at long range because of his shooting abilities, not because he is an engineer. It's not about formula's if you can't point the rifle properly and break the trigger without disturbing the rifle. It's a shame people here don't see the value in plain and simple marksmanship fundamentals, I guess since you can't throw money at that problem and fix it people don't want to participate. This is the deal, I see lots of tactical shooters that are one time NRA prone shooters. one time is all they can stomach since holes in the target don't lie.

I know i'm rambling and you could care less, maybe someone else will see the value in concentrating on reducing the biggest errors first and ingraining that into subconscious action and letting the minutiae fall into place.

 

[damoncali]

Xcount, I hear you - and I always try to put out good info. In this case I fell a little short and gave short range info to a long range question. I feel bad about that because someone might have gone out and wasted a round or two based on that info and come away more confused, which is the opposite of what I want. However, I don't feel bad about talking about small, real effects. Spin drift, coriolis, vertical wind deflection. They're real and if you understand them, you can know to discount them or not. Judging by the number of posts where people are wondering why their zeros move around at different ranges and under different conditions, people lack this knowledge. Of course, if you're blaming spin drift for two minutes, you don't quite get it. The solution to that is not "don't worry about spin drift" it's "understand spin drift". Which brings me to the shot I described in an above post.

I take issue with your characterization of my 600 yard shot. What I said was that it was a "slightly high nine", and what I mean by that is a few inches high - not up in the corner of the nine ring on a 45 degree angle. Do I know 100% that it wasn't me? No - you never do, but it was a damn good hold (that's the only reason I remember this particular shot so well), and it was F class, where holding isn't typically the challenge. But that result is exactly what you would expect to see from vertical wind deflection, so I'm pretty confident that the hold that I had was good. (Perhaps too good, since I missed such a big wind shift right in my face). Why that's important is that I can stop worrying about how I screwed up the hold or how my elevation might be off a click or two. I screwed up the wind. Simple.

It goes without saying that fundamentals, wind reading, etc, are what matter the most. But we all practice those things. They're not complicated even if they are difficult. There aren't a bunch of posts about them because there isn't much to write, and writing is a poor medium for that stuff anyhow. Video, or better yet, in person training is far better. For ballistics and equipment discussions, this format is great. And why not maximize everything to get the very best scores you can? I can only shoot so much. I can read all day long.

 

[Lowlight]

There is a reason these math formulas and scientific theories don't work for everyone equally across the board.

The Human Elements trumps all of it... what they model in a vacuum and by using a barrel in a fixture is not the same once you add the shooter to the equation as it changes the model in a gross and unpredictable way.

if we were shooting heavy bench rest rifle we could probably spend more time discussing this type of math and science, but since we are driving the rifle, our influence outweighs a whole lot of this stuff. That includes SD, CE, Cross Wind... If it was so predictable and necessary, every gun in the US would be barreled with a left hand twist and not a right. Especially rifles that were set up for ELR use.

Once "you" the shooter have honed your skilled down to being a consistent, a guaranteed 1/4 MOA shooter, and by that I mean at all distances you engage, the odds you being able to utilize these effects are really, really small. Noise is a great term to use.

As noted, too many quote these factors as if they are seeing it on a daily basis. Meanwhile they can't clean a 2 MOA field course, let alone dope the wind to 1 MPH out to 1000 yards. They shoot a 4 MOA+ target at 600 yards and miss 25% of the shots then turn around and quote you verses from Bryan Litz as if. If you can't drop down and on command hit with every shot on an 18X30 IPSC target @ 800 yards, you might want to get out and shoot more. Adding .2 mils of SD is not gonna help you, neither is worrying about dissimilar wind drift.

We took a class of 10 shooters, zeroed a rifle in a lead sled at 100 yards and then let every student fire a group at a 1" dot. The variation between shooters, from left to right on just the horizontal plane was 4 MOA. This is why quoting this stuff is meaningless. With a class of 20 shooters all with Mk11 MOD0 and M118LR at 1000 yards, shooting at the same time under the same conditions we saw 2.5 Mils of variation in the wind holds used. The sole left hand shooter used 1.5 Mils to hit the target, the rest varied to as much as 3.5 Mils on the same. Telling...

The Human Factor ... so get out and shoot, and worry about the minutiae later.

I have all that crap turned off each and every time i use my ballistic computer. At distances beyond 1500m, I use 1/2 of what the computer says, but only if the wind is below 5MPH, if it's above I don't use it at all.

 

[damoncali]

Maybe human nature being what it is, some people are held back by this sort of theory. I find it liberating in that it frees me to focus rather than worry or wonder. I can certainly acknowledge that I may be the weird one, though.

 

[KYpatriot]

KYPatriot,
I replied to a guy that was blaming high 9 on a crosswind, that's b.s. He had a high 9 because that is where he pointed the rifle. Good on him for realizing he was talking about something else and that crosswind effect is not the big factor he was thinking it was. It's not a pissing contest when someone that knows what he is talking about is trying to teach someone, and that someone acknowledges his mistake.

I find it interesting how many of you guys here love to quote from Litz' book after he specifically states marksmanship is the biggest factor in your rounds hitting where you want them to. Brian is a National Champion at long range because of his shooting abilities, not because he is an engineer. It's not about formula's if you can't point the rifle properly and break the trigger without disturbing the rifle. It's a shame people here don't see the value in plain and simple marksmanship fundamentals, I guess since you can't throw money at that problem and fix it people don't want to participate. This is the deal, I see lots of tactical shooters that are one time NRA prone shooters. one time is all they can stomach since holes in the target don't lie.

I know i'm rambling and you could care less, maybe someone else will see the value in concentrating on reducing the biggest errors first and ingraining that into subconscious action and letting the minutiae fall into place.

You don't need to explain yourself to me, I agree with what you are saying. There are no shortcuts; you only learn to shoot by correct, disciplined practice regardless of the physics. All I was pointing out was that it is ok for a new shooter to motivate himself with whatever it is about shooting that interests him. You keep implying that just because I enjoy the physics that i dont have the proper priorities on what makes a shot. Why do you think I could "care less" or that it would take someone else to the see the value of what you are saying? I think it you read my post without being defensive you will find nothing you disagree with.

Why do I even care to reply? Because it is important to me that people in this country continue to shoot and pass on the accumulated knowledge and discipline of the gun. It has value to people and our country in many ways. As a Highmaster you clearly have learned some important lessons and the discipline to employ them...why not use the same discipline to encourage a new shooter and redirect their priorities without ostracizing them or hostility at their particular angle of interest? For all I know maybe Bryan IS a national champion because his interest in aerodynamics and ballistics lead him to take up a sport expressing that interest...then somebody like you came come along and carried him to the next level teaching him how to DO what he has read and studied.

This isn't directed at you personally necessarily, its just an annoying trend I have seen where good experienced shooters have no patience whatsoever in their manner with new shooters and turn people from the discipline. I know it is annoying how everyone wants to think they are missing because of spin drift and there is green zombie ammo everywhere and $6000 weapons that cant hold a 2 MOA group at 200 yards because the shooter doesn't know where to begin. But I know this...if we can't control ourselves we are going to end up with a country where we have a few badass old men that can shoot and millions of soft men in the prime of life that have never pulled a trigger except on an xbox. Not where we want to go. I have several in my circle that are now getting to be decent long range shooters who were previously Fudds. I am as proud of that as any shot I've made, and since I don't do this for a living it is likely to help the country more than any shot I will ever make as well.

 

[KYpatriot]

There is a reason these math formulas and scientific theories don't work for everyone equally across the board.

The Human Elements trumps all of it... what they model in a vacuum and by using a barrel in a fixture is not the same once you add the shooter to the equation as it changes the model in a gross and unpredictable way.

if we were shooting heavy bench rest rifle we could probably spend more time discussing this type of math and science, but since we are driving the rifle, our influence outweighs a whole lot of this stuff. That includes SD, CE, Cross Wind... If it was so predictable and necessary, every gun in the US would be barreled with a left hand twist and not a right. Especially rifles that were set up for ELR use.

Once "you" the shooter have honed your skilled down to being a consistent, a guaranteed 1/4 MOA shooter, and by that I mean at all distances you engage, the odds you being able to utilize these effects are really, really small. Noise is a great term to use.

As noted, too many quote these factors as if they are seeing it on a daily basis. Meanwhile they can't clean a 2 MOA field course, let alone dope the wind to 1 MPH out to 1000 yards. They shoot a 4 MOA+ target at 600 yards and miss 25% of the shots then turn around and quote you verses from Bryan Litz as if. If you can't drop down and on command hit with every shot on an 18X30 IPSC target @ 800 yards, you might want to get out and shoot more. Adding .2 mils of SD is not gonna help you, neither is worrying about dissimilar wind drift.

We took a class of 10 shooters, zeroed a rifle in a lead sled at 100 yards and then let every student fire a group at a 1" dot. The variation between shooters, from left to right on just the horizontal plane was 4 MOA. This is why quoting this stuff is meaningless. With a class of 20 shooters all with Mk11 MOD0 and M118LR at 1000 yards, shooting at the same time under the same conditions we saw 2.5 Mils of variation in the wind holds used. The sole left hand shooter used 1.5 Mils to hit the target, the rest varied to as much as 3.5 Mils on the same. Telling...

The Human Factor ... so get out and shoot, and worry about the minutiae later.

I have all that crap turned off each and every time i use my ballistic computer. At distances beyond 1500m, I use 1/2 of what the computer says, but only if the wind is below 5MPH, if it's above I don't use it at all.

There you go Buzz, while this thread has gone beyond your original question, you have seen the math on why its in the noise, and several more accomplished shooters than I have shown from experience why it should not be of much concern to you.

 

[Lowlight]

Look at it this way...

There would be no need for a Tracking Point Rifle with a computer released trigger system if this was simply as quoting McCoy or Litz.

If the ballistics / science were perfect for every shooter & rifle system, meaning, if what the theories suggest actually worked as cut as dry as following the formula suggests, we would not have to true software and every ballistic computer would give the shooter a first shot hit no matter what.

I heard it at SHOT from someone who was a AIMEE Ballistic Computer fan, where they said, you only ever use "true data" meaning what the chronograph says, what the BC is listed as, and it works. I asked them how the computer knew the correct MV before the shot was taken ? To include the ES / SD of the load (you do insert that info after all) and how they knew what the exact twist of every barrel was, not that you had a 1-12 but whether it was really a 1-12 or maybe a 1-12.2, or 1-11.9 as accordingly all that should matter too. variation in steel, tool sharpness, etc

All this assumes a vacuum no external factors until you put in those external factors, and then, if you add in wind, it assumes the wind is constant from muzzle to target.

99% of what we use is an average based on a tiny percentage of sample data. Some of it, was written more years ago than most of us were born. They just continue to repeat and regurgitate the same thing over and over again. It's the exact same justification why someone will say G7 is better than G1, yet everything they use around the G7 is the same old information. We can clearly demonstrate that both are capable of getting the job done, so how can the science of the justification hold true if they are both doing the exact same thing ? Well because it's an average and they are hoping the majority will fall within the error factor.

Shoot more, worry less... you can every bit as successful with nothing more than practice and a piece of paper & pencil. Write it down, when you see it again, repeat.

D O P E

Data On Previous Engagement

 

[Xcount]

.....

I take issue with your characterization of my 600 yard shot. What I said was that it was a "slightly high nine", and what I mean by that is a few inches high - not up in the corner of the nine ring on a 45 degree angle. Do I know 100% that it wasn't me? No - you never do, but it was a damn good hold (that's the only reason I remember this particular shot so well), and it was F class, where holding isn't typically the challenge. But that result is exactly what you would expect to see from vertical wind deflection, so I'm pretty confident that the hold that I had was good. (Perhaps too good, since I missed such a big wind shift right in my face). Why that's important is that I can stop worrying about how I screwed up the hold or how my elevation might be off a click or two. I screwed up the wind. Simple.
....

Now there seems to be a shift in the conversation. The OP talked about crosswind causing elevation errors, not talking about vertical wind. Two completely different subjects, one is significant the other, what I believe he was talking about, is insignificant in the grand scheme of shooting 1moa/2moa targets out to 1k. IF you're now talking about vertical wind then that is not what I was calling b.s. on.

As far as your one shot is concerned if you think it was a vertical wind issue then so be it, it does happen even on flat ranges. Spin drift and coreollis effect and that stuff don't make 9's on 2 moa targets, is all I was harping about.

Sorry to say that there are people that are 100% on their calls, meaning even if they blinked when the shot broke they know it and can say "I missed the call" and they will base their next shot with that in mind. That is where were all need to get to, lofty goal but it is achievable. Some of the guys I shoot with have no surprises, they know every time where the rifle was pointed when the shot broke, sometimes they don't like it but they are not surprised. me? not so much.

 

[KYpatriot]

LOL back when we were rolling in dropping "dumb" bombs using manual or even computed deliveries, which is very similar to the track point technology, there was a post mission logbook to fill out to help "true" the system because of the same error and tolerance stacking we are up against in long range shooting. I would get frustrated because some guys would add some unneeded correction to the book to ease their ego about that bomb the range officer called "unbelievable at 12". This would cause mx to add an error to the system, so the next guy that actually drove the jet right would miss. All that is gone now with the drive by shooting they call JDAM...thread creep but its interesting to me how may things from that world directly apply to the art of shooting a rifle. Namely, the first step to being a good fighter pilot or good shooter is being brutally honest with yourself.

 

[Xcount]

Look at it this way...

There would be no need for a Tracking Point Rifle with a computer released trigger system if this was simply as quoting McCoy or Litz.

If the ballistics / science were perfect for every shooter & rifle system, meaning, if what the theories suggest actually worked as cut as dry as following the formula suggests, we would not have to true software and every ballistic computer would give the shooter a first shot hit no matter what.

I heard it at SHOT from someone who was a AIMEE Ballistic Computer fan, where they said, you only ever use "true data" meaning what the chronograph says, what the BC is listed as, and it works. I asked them how the computer knew the correct MV before the shot was taken ? To include the ES / SD of the load (you do insert that info after all) and how they knew what the exact twist of every barrel was, not that you had a 1-12 but whether it was really a 1-12 or maybe a 1-12.2, or 1-11.9 as accordingly all that should matter too. variation in steel, tool sharpness, etc

All this assumes a vacuum no external factors until you put in those external factors, and then, if you add in wind, it assumes the wind is constant from muzzle to target.

99% of what we use is an average based on a tiny percentage of sample data. Some of it, was written more years ago than most of us were born. They just continue to repeat and regurgitate the same thing over and over again. It's the exact same justification why someone will say G7 is better than G1, yet everything they use around the G7 is the same old information. We can clearly demonstrate that both are capable of getting the job done, so how can the science of the justification hold true if they are both doing the exact same thing ? Well because it's an average and they are hoping the majority will fall within the error factor.

Shoot more, worry less... you can every bit as successful with nothing more than practice and a piece of paper & pencil. Write it down, when you see it again, repeat.

D O P E

Data On Previous Engagement

Lowlight,
i've often wanted to ask your thoughts about all the technology coming out and about all the guys constantly doing OCW testing and being convinced that a load .012 off the lands shoots significantly better than a load .015 off. I mean the Marine Corps uses mass produced factory ammo to send guys in harms way with, do they lot match ammo to rifles? I bought a rifle from a 2112 and he tested it at Quantico using factory ammo, it shot under .75moa and he said it met USMC standards and I have no doubt it would do the job. so what is your thought on all the testing and buying gadgets instead of shooting?

thanks.

 

[seanhagerty]

KY patriot, do not call him an eagle driver. He flies a bus for a company that tends to not hit the right runway.

Lets see if I understand what I have distilled here:

• Shoot your rifle a lot.

• Pay attention to where you hit and where you miss.

• Use experience from both these items to get better.

I think I got this. Thanks Guys.

Sean

 

[damoncali]

I don't get the either/or. Why must someone read *or* shoot? Why must someone simply rely on empirical results *or* try to understand why the bullet does what it does? I shoot as much as my schedule and budget permit and try to make as many matches as I can. It's no where near as much as I'd like, but I'm a civilian with some fairly run of the mill obligations. I don't claim to be a super distinguished grand high master. But I do know what I'm doing.

Why do we believe that McCoy et al. are more or less correct and these small effects are real, but the second someone says they observe it at the range the reaction is "BS - you just missed."? I don't have safes full of rifles, but each one I do have has a zero that moves to the side as I go down range, whether I change position or not. Just a little bit, but they do it. That, people seem to accept. But if you call it spin drift, you're all of a sudden blaming your gear for your misses, spending too much money on gadgets, reading too much, and basically being un-American.

It's true, the bigger your target and the farther away it is, the less all this stuff matters. I wouldn't know that unless I knew about it in the first place, though. And I didn't have to shoot thousands of rounds to learn. The rounds I am able to fire count more when I'm not screwing around trying to figure out if my zero moved because of my position, a bad sight picture, or if it might move again for some other unknown reason. I know why it moved - spin drift - and I can verify it pretty easily because of all those books that everyone is so intent on dismissing.

Are gadgets worth it? Depends. Are you trying to hit an IPSC target? .75 MOA plenty good. Are you trying to compete in F open? That 3/4 minute rifle will put you at a disadvantage. I know this for two reasons - one: I've shot F class before at a high enough level with a half minute rifle and I know intuitively (that is, from experience) how much a 1/4 minute means in terms of x counts and even 10's. two: I read about it in Bryan Litz's book, which builds on McCoy's book, Which builds on McShane, Kelley, and Reno's book, which builds on Isaac Newton. There is no either/or here.

Granted, this is my personality. I did the same thing with scuba diving when I did it professionally years ago. I learned everything I could about diving physiology. Did it make me a better diver? No, not really, but it did make me a tad safer, and gave me enough knowledge to know that doing it long-term would not be a positive thing for my health. Not everyone is like that. Some people may just get overwhelmed by all the info or prefer to keep it simple. To each his own, I suppose.

 

[Lowlight]

@Xcount

I suppose it depends, I don't reload myself and shoot factory or semi custom ammo only. In a 308, other than cost saving I see very little need to reload. (that changes if you want to shoot something like the 185 Juggernaut) But for a 175gr load, I shoot factory.

I use what pretty much everyone else does when it comes to other loads as well, like my 6mm Creedmoor load, it's George's load.

The consistency can certainly help, it won't hurt, anytime you can get single digit SDs. But the endless load development people do, I don't believe in. I think it is an excuse to not shoot in public or competitively.

Even ELR wise, I use what is off the shelf, and with factory Hornady 285s, when measuring managed to hold 6" of vertical at 1500m on paper. My groups were every bit the same as the guys there who rolled there own.

But again, if you have a solid, consistent load, that's definitely is better than not. I honestly never had a factory 308 load that wasn't under 1/2 MOA with my rifles, all of them, and have a few that with factory ASYM ammo have been below 3/8s of an inch.

@damoncali

it's very easy to separate the guys who are regurgitating information and quoting stuff as fact vs guys who have shot this stuff and know the difference. If I am talking to David Tubb and he is telling me about it, I believe he is seeing true effects, verses the guy with the stock 5R claiming to need 1/2 MOA of SD at 600 yards. It's really quite simple, and why you see push back.

And because of what I said above, about the Human Factor, I find it odd that people who have so much trouble with their IPhone app getting it to match their system, then want to turn everything on and needs the SD values being presented as fact. The SD used in these ballistics Apps are a basic flat rate number with no real calculation or necessary information. It's the guy who has CE turned on but no Latitude information or compass bearing to target in the computer... you just know. What they are seeing is not "it" In this case Gerald Perry had it right in ExBal, he called it Shooter Drift and required you actually shot and measured the deviation. I personally don' t buy any of the SD stuff, as I have yet to see it as true information. (the USMC ignores it, always has, not in a single manual) If it was so cut and dry we would be missing our target by NOT using it, we do not. In my opinion, it's a sub sonic effective and not nearly as much at super sonic speeds as being reported. When people quote off iron sights from the 1900s, the bullets were going sub sonic most of the way. Huge arc.

Same with CE, i believe everyone is wrong, because nobody takes into consideration the Earth drags it atmosphere with it, so the speed of the earth spinning is not the same because at the surface the air boundary layer travels with us. So if you figure the speed of the Earth's rotation, it won't work. Show me the offset by this boundary layer moving ? The last time I read the news, the guys floating above Earth in balloon enhanced lawn chairs are going with the wind, and not winding up in the Pacific Ocean. Same thing with the little kids launching GoPros on weather balloons and retrieving them, if the number were as big as we try to say, all those would be in the Pacific Ocean. If you feel a 2 second TOF is moving the target away from you, how come every chimney in the world does not leave a streak of smoke 10ft above the ground.

It's buzz words, like when you meet a guy and he goes on about Humidity, or he is Black Ops guy, same thing. They go on and on about humidity and how they account for it, then repeat it backwards. They believe because we feel heavier the bullet is being negatively effected by high humidity. So they say, high humidity increases drag. At that point you roll your eyes and walk away.

Pretty simple to separate the shooter from the reader. Mention, SD, CE, Humidity... and I am off to hit on your wife. I would rather the conversation turn to her nails or shoes.

 

[damoncali]

Fair enough. I believe in spin drift and believe I have observed it. Not enough to cause a miss on anything but a tiny target, but enough to see. When I see something, I wonder where it comes from and try to correct it if necessary. Knowing (or at least thinking I know!) that what I am seeing is drift keeps me from digging in the wrong stuff. It helps me grow. Like I said, if I see my zero move in a way that is consistent with properly calculated drift (not made up numbers), then I can reasonably assume that my position is consistent. That's useful knowledge to me, even if I could just write it down and be done with it. It builds confidence in my techniques.

I also believe in CE, although I won't claim to have witnessed it. My range only goes one way, and it doesn't go far enough. Frankly, that one seems pretty academic to me. And I'm pretty convinced engineers are to blame for the humidity thing. The natural thing to do when calculating air density is to factor in humidity. It's just what you do, because why wouldn't you? It's the correct way to do it. Because they sort of instinctively include it, you need to input it. Because there's an input, they say, "What the hell, let the user input it", assuming the user knows what the hell he is doing. Now, one thing I've learned working in the software business is that the user almost universally does not know what the hell he is doing. So blame my people (the engineers) for that one.

And I'm starting to get that there are some topics that just cause red flags to go off so violently that I really ought to be careful about when I try to bring them up legitimately (and not fuck up the details as I did way above in this thread). Sometimes I feel like I'm doing more harm than good.

 

[Pinecone]

WRT SD and CE, I would go to talk to and look at the REALLY long range shooters. The shooters that shoot in excess of 10 miles. BIG guns. Like battle ship and rail road guns.

I remember reading about the German WWI rail road gun, that they had to take into account the earth rotating while the round was in flight for a west to east shot.

That does NOT mean it MATTERS for rifle shots, it just validates the occurrence.

IMO, you can arrive at the same place by several methods. One is the math. One is empirical (shoot a lot). And finally you can do both.

But I have mentioned before, the nut behind the trigger, or wheel, or tiller, or bat, or racket makes more of a difference than the other factors.

And real men drops bombs with nothing more than a pipper and SKILL.

Former A-10 driver here.

 

[Lowlight]

Big guns are a false argument, it's going well into the atmosphere, it's miles and not yards, and it's time of flight is longer.

They lob, not shoot right next to the earth. If you said tanks, it would be close to fact. According to a naval gunner, the 16" guns of a battleship has 4ft of SD at 26 miles. Play that number back. We use 1ft at 1000 yards.

A 308 at 1000 yards with a 1.5 second time of flight, it's only 15ft above the ground. Contrast that with the miles or artillery... Not the same,

if it was a concern something to worry about, we'd be using left hand twist barrels.

Not to mention your right handed shooter influences the horizontal much more as I have noted. 1MPH of wind is 10" at 1000, if you can't dope that how can you say what it is.

Not saying it's not there, but certainly not to the degree inside the super sonic range being reported.

i talk to several different ballisticians and it's getting like weather modeling, a 100 different projections.

 

[Jedi]

The sole left hand shooter used 1.5 Mils to hit the target, the rest varied to as much as 3.5 Mils on the same. Telling...

Have always known us lefties need less dope, the wind gods like us more

Shoot more, sweat the BS LESS

 

[Lowlight]

Which is very telling...

It demonstrates beyond any shadow of a doubt the values are being exaggerated by the shooter.

Any time someone claims these effects are necessary to be considered or else... just drag out a left handed shooter and you can show them the exact opposite.

 

[KYpatriot]

Good informative thread.

BTW if for anyone interested in ballistics, you could spend a lifetime studying the IOWA class battleship 16in guns that Frank mentioned. The analog fire control system is, in one word, awesome. The ballistic solution had to consider the relative motion of the ship and target, pitch and roll of the ship, and the usual external ballistic factors discussed here including air density, muzzle velocity, coriolis and spin drift (although this was less of a factor since the RPM of these rounds was only a fraction of our bullets, a twist of 1 in 400 for a 16in shell gave a little over 4000RPM, a 180 berger in a 9 twist at 2900 is about 232,000RPM) Just imagine wind corrections for a relatively low BC projectile at 80sec TOF. The engineering problems they solved to even get close in the days of slide rules are incredible. I attached a picture of their SUV sized iphone ballistic computer, and that doesnt even show a room full of other adjustments:

I think it fair to say we are living in a golden age of long range shooting. We are the beneficiaries of amazingly consistent manufacturing techniques for barrels and actions, the most uniform high BC bullets and consistent powder ever, trajectory calculating tools that can fit in the palm of a hand, the availability of excellent instruction in shooter fundamentals, all at a price enabling almost anyone to participate.

It is a good time to be a shooter, even considering the external pressures on the scene. Lets all enjoy it while we can!!

 

[Lowlight]

Here, I had this saved,

It does have an effect, but...


From Canadian Manual:
B-GL-306-006/FP-001
FIELD ARTILLERY
VOLUME 6
BALLISTICS AND AMMUNITION


“In manual computations, rotational effects are not applied in Canadian gunnery procedures at ranges under 15000 metres, as the additional accuracy achieved does not justify the time expended.”


So, if they don't worry about it with artillery under 15,000 meters (that's 9 1/3 miles folks), I doubt if we need to be concerned with any calibers that we shoot at any range.