Having a friendly bicker/banter at the lunch room table. When a bullet leaves the barrel gravity immediately begins its affect. We all know that. So trajectory is arced upward even on the flattest shooting cartridges.

But... this old feller is telling me that like a pitcher throwing a baseball with spin, (a floater?) (I know NOTHING about baseball) that some bullets with high rotation spin, the bullet will dip down and then lift for a slight sine wave affect on the bullet trajectory. I said NO WAY!

So what do the truth be?

BS "ballistics."

I've also heard barber-shop and bar-stool ("BS") "ballisticans" aver that a bullet takes an upward hop the instant it exits the muzzle of a dead-level barrel. This notion is as nonsensical as the trajectory that a stuttering jailor in my mother's home town used to claim for his "b-b-b-big p-p-pistol" to awe his "guests:"

"Sh-sh-shoots a z-z-zig-zag, r-r-ramblin' ball. When you z-z-zig, it z-z-zigs. When you z-z-zag, it z-z-zags. C-c-can't miss!"

Every boy in town wanted to see that thing shoot but never got a demonstration. I'm still disappointed.

<img src="/ubbthreads/images/graemlins/grin.gif" alt="" />

.

from the time it leaves the barrel it only goes down, believe it or not,,,,

High rotational velocity can create an airfoil of sorts. Here's a little science project: take a bic pen, the round one, pull out all the guts and end cap,leaving an empty tube. Place on a hard, smooth surface. Press HARD with the tips of your fingers using both hands and roll it back towards you, squeezing it out. It may take several tries to get an even release. If you do this right the tube will climb, often go into a complete loop-de-loop, among other things. I don't believe you can make a baseball "climb" or "rise". Just because you put wings on something doesn't mean it will fly.

I'll add ... in relation to the bore axis.

Dixie, Are you talking about the bullet eventual drift left due to bullet RPM's at long range?

I have heard this can happen at long range but I've never heard any proof to prove or disprove it.

As I understand, the bullet beings to drop the moment it leaves the muzzle. If it begins to drift left because of bullet RPM's, who knows. I doubt there is a rifle/shooter that could be so consistant as to give us the truth. I think wind, decay of accuracy and shoter error will show up before bullet drift from RPM's.

CM

in re: the bic pen experiment:
i believe it makes a difference if the rotation is parallel or perpindicular to the axis of travel

the only way it can go up is if a wind (turbulence) caused it. and in the real world it would very little unless your shooting with 50 mile a hour winds

I'm going out on a limb here so feel free to saw it off. BUT, it is my understanding that lift can occur on a bullet if there is a cross wind. The bullet is rotating so the relative velocity across the bottom of the bullet will be different than across the top. This is exactly how an airplane wing works. Now if the wind blows from the opposite direction then you will have negative lift resulting in greater bullet drop.

It is my understanding that this "lift" problem is more significant on arrows given their slower velocity and greater surface area.

I don't have any data to support my comment but the basic phyics appear to be sound.

this possible lift would be more than likely happen just when the bullet leaves the barrel, the farther out the bullet gets the more it is dropping (dropping faster) the more wind it would take to lift it.

it would take a strong wind to do all this

This is some of the stupidest [bleep] I've heard in a long time.

When a bullet is spinning, to the right for example, the top of the bullet is rotating to the right, but the bottom of the bullet is rotating to the left. This would produce exactly equal and opposite forces in opposing directions.

This is apples and oranges to the baseball comparison, because the baseball is rotating in the same direction as the flight of the ball.

I think it is hysterical that every time some guy comes on here and wants to get an explaination of some kook theory, it is always his "friends" that say the kook theory is true and he wants some backup to disprove it.

So, what we need is a bullet that tumbles, so we can compare it to baseballs!

Who's on first?

Well, going out on a limb here, but the Army Aerial Gunnery Manual teaches us about something called "The Vertical Plane Gyroscopic Effect." Essentially, firing off axis, in a direction other than that of the helicopter's travel, induces a crosswind. With A right crosswind, gyroscopic precession (force applied to a rapidly spinning object takes place 90 degrees to the force, in the direction of rotation) will cause the bullet to hit high, and a left crosswind would cause it to hit low, assuming the bullet is turning clockwise as viewed from its base. As far as sine wave trajectroy, I don't think so.

John

I don't know.


(Actually "Who's on first." is a statement . ... not a question <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />)

there is lift were the bullet is actually lift above the shooting plane (axis) or what seems like lift, but the bullet isn't actually lifted, but the drop rate is reduced even thou the bullet never actualy goes above the plane

Bosie..my High Power 1000 yrd notes would tend to agree. Elevation differences of 1/2 too 1 min. {6-10 inches} are indicated when a cross wind is coming from 1-3 o`clock compaired to 9-11 o`clock. This changes with wind velocity. I don`t know why it happenes, but it does. Some of the most difficult shooting I`ve done at distance is in light and variable conditions. seeing the marage move from right to left, then left to right. making a windage adjustment here without a corresponding elevation adjustment will move you out of the ten ring. I shoot a 308 with 175 Breger VLD`s BTB.
I should think some of our 1000 yrd benchrest shooters would have some input on this subject too.

Baseballs can and do some things that seem artificial or contrived. Curve balls do actually curve-its not an illusion! The key is the stitching creating a differential in air pressure causing the ball to move in the direction of lower pressure. Even I could through wickedly hooking curves with a wiffle ball <img src="/ubbthreads/images/graemlins/grin.gif" alt="" />

Similarly, golf ball dimples allow drives to go farther than a smooth ball would allow.


--Mike

Even my friends who saw it remember the wicked curve that I put on a half-rotten apple in 1952. For no special reason, I put a hard counter-clockwise spin on it as I pitched it, as hard as I could throw it, at a power pole out by the street. It curved out wide to the left, then came back in to the right, and plastered instant apple sauce smack dead-center on that power pole. (No, I didn't pitch another apple. It pays to know when not to push your luck!)

.

That was great wisdom Dr Howell.

George, he's on third. <img src="/ubbthreads/images/graemlins/tongue.gif" alt="" />

I wondered if a very LOW BC bullet launched from a magnum pistol, would travel in an arc, but on the downhill side of the arc the drag would be great enough to slow the gravitational (constant) pull? Not exactly "lifting" it, but slowing it. Now this is probably some BS conjured up in my simple little mind, but maybe its worth a thought.

As far as switching crosswinds at long range, wouldent the yaw of the bullet have an effect on bullet drift? A bullet that leaves the barrel with a clockwise spin, tends to pull to the right, not noticible at close range, but its worth about one minute of angle at 1000yds

cas, drift is calculated for arty, it's the spin of the round that makes it drift. Drift is a funcrion of range.

Hondo, you are not going out on a limb at all. Understanding that "gyroscopic precession (force applied to a rapidly spinning object takes place 90 degrees to the force and in the direction of rotation ) is the key to understanding long range gyroscopic spin drift. Bullets from a rifle with right handed twist will drift to the right, and bullets fired from a rifle with left handed twist will drift to the left. At 1000 yards gyroscopic spin drift can be as much as 13" in a 30-06. It is counterintuitive for most people to realize that the force applied to a bullet isn't directly in the opposite direction (i.e. 180 deg) to an applied force.
Vertical drift resultant from a crosswind is approximately 1/10th of the gyroscopic side drift. The Research Lab at Aberdeen considers the effects so small the they only list it's effects in firing tables for guns over 8" bore. A stronger crosswind velocity from the forward motion of a helicopter is why Hondo would have seen them in his Helicopter firing tables.
The Physics at first seem counterintuitive but they are established and proven facts. Bullets do drift at long range in the direction of the rifling twist and there is a very small vertical drift in crosswinds. Usually however the total effects are neglible compared with other external factors such as wind drift and bullet drop. And aren't enough to worry about at sane hunting and normal shooting ranges...............DJ

Well said--you saved me alot of typing... <img src="/ubbthreads/images/graemlins/grin.gif" alt="" />

You can't fight Mother Nature (i.e. gravity).

Were one to set up a rifle with the bore axis perfectly level, while also holding an identical projectile in one hand at the same height, both bullets would hit the deck at the same instant when fired and dropped simultaneously. The downward vector doesn't care how fast its perpendicular travel is; down is down.

RSY

yep it's going down, it maybe possibe for STRONG up draft to raise it just after leaves the barrel

Having shot sixguns quite a bit at long range, I find that certain bullets fly very well indeed inspite of their low BC. I don't know ballistics all that well and this thread has me lost as it appears that I am not sure what everyone is talking about, but I have seen amazing things from heavy for caliber bullets fired at subsonic muzzle velocities from sixguns at real long range. I've shot some 405gr cast bullets from my Linebaugh 45 Colt starting at just over 1000fps and seen some amazingly flat trajectories to 1000 yards. I beleive these bullets and similar bullets behave themselves better than many rifle bullets when range gets way out there.

I know some sixgun shooters that could shame many rifle shooters once the distance went beyond 300 yards.

CM

Of course you can fight Mother Nature (i.e. gravity), Airplanes fly all the time don't they? She'll win eventually but some things can leave the ground.
It's true that a perfectly horizontal bore shooting a bullet would hit the ground at the same time as one dropped at the same exact instance but only in the absense of other forces.. Airplanes fly because temporarily Lift superseeds the pull of gravity. Forces on a bullet such as crosswind spin drift could actually cause a horizontally fired bullet to very slightly impact later.......DJ

Idle thoughts from idle people are as worthless , as the idle people

If you want a good understanding of drifts get a copy of
"Rifle Accuracy Facts". It has the best explaination of
"Wind Drift" that I have ever read. No it's not the wind blowing on the side of the bullet.
Good luck!

Maybe someone already wrote this, must confess I didn't read every post.

Baseballs curve, move, or float in un-natural ways because of the seams. I haven't checked all my bullets yet, but the Noslers and Hornadys I did look at don't have any seams. I think they build them that way on purpose, to reduce drag I reckon.

My bad ... the error of typing too fast!



Third base! <img src="/ubbthreads/images/graemlins/grin.gif" alt="" />

[The Physics at first seem counterintuitive but they are established and proven facts. Bullets do drift at long range in the direction of the rifling twist and there is a very small vertical drift in crosswinds. Usually however the total effects are neglible compared with other external factors such as wind drift and bullet drop. And aren't enough to worry about at sane hunting and normal shooting ranges...............DJ [/quote]

The long range drift in the direction of the rifling twist was reported by Elmer Keith many, many years ago. Actually, I read it in a book or article by Keith so he probably did not "discover" this. Anyway, this type of info was apparently well known to the old military shooters when Elmer was a member of the National Guard rifle team back in the Twenties (Montana IIRC but could have been Idaho).

Once again going from memory of books read long ago so I may have some minor details wrong, but the gist is that this effect has been well known for quite some time.

Sorry for not being more specific. We're talking about bullets, right?

Bullets are symmetrical, airplanes are not (hence their ability to create lift). Were you to install an upper airfoil the same distance above the centerline of the aircraft, with the same attitude relative to center, as the one below the centerline, the plane would not fly. The upper "mirror" wing would cancel out the lift of the lower wing, thus giving gravity the decisive upper hand.

Apples and oranges. A bullet is not an airfoil.

RSY

RSY, No a bullet is not an airfoil and airplanes don't spin at over 100,000 revs per minute either.
The analogy is to show that there are forces that act against the pull of gravity. In airplanes that force is lift, in bullets it is gyroscopic spin drift. The two are completely different forces but both can act in opposite direction of gravitational pull. Gyroscopic spin drift is also a minor enough force that it's rarely noticed...but it is there nonetheless...........DJ

Don't forget the Coriolis acceleration! It matters which direction of twist you have in your rifle and the amount of drift in the northern hemisphere compared to the southern hemisphere. <img src="/ubbthreads/images/graemlins/wink.gif" alt="" />

Sierras older reloading manual had good discussions of exterior ballistics, I presume the current editions do too.

jim

Jim...Keith may have been remembering some of the Springfield 45/70 Trapdoors. The rear sight was made to accomadate this drift at long range, as the sight was made with an automatic drift compensator built in. As you moved the elevation up, the sight moved to the left. Check it out..

so gravity still exscists, but the bullet could over come its froces and be shot around the wrold right back to point it started at. youd have to watch your back on this one. i will not belive that bullet would be in the same place even if wind didnt effect it. in the dead calm that bullets spinning would more than likly make it end up miles from where where it started.

now if there was no gravity that same bullet i belive would come true and would end up right were it started. spinning or not.

but wait we now have the moons gravitational pull to deal with, hmmmmmmmmmm all to confuseing, i have no idea what im talking about, i just shoot.

Evan

I think the answer to all the above is to design a rifle that shoots apples at telephone poles. Then the telephone pole gets rotten from all the apple juice on it, topples and falls on the game, killing it. Either that or you fly an airplane through the chest cavity of a deer.

I have one question -- do you have to put a lead tip on an airplane to get it to expand, or do they make a TSX Cessna? (I guess that is two questions.)

Strange we ever hit what we're shooting at. Last time I hunted out of a helicopter, I wondered why I couldn't hit what I was shooting at. I thought it was the speed I was travelling. ;-)

Harold Vaughn has proof positive that a cross wind does create lift on a bullet, for part of the trajectory. The results of his experiment are on p197 of his book (see attachment link). The image shows both horizontal displacement and vertical displacement from a crosswind. Absent lift, it is very hard to explain his results.

The fundamental rule of physics is that anything that happens must be possible. The data are never wrong. It is up to us to come to terms with the data.

Here is my attempt to reconcile with the data:

A bullet fired horizontally in a cross wind will align its axis so that the axis is parallel with the vector sum of the crosswind and the bullet velocity. The drag vector now points directly out the bottom of the bullet, and is not parallel with the trajectory. It now has a vector component in the direction of the wind. That, not the wind blowing against the side of the bullet, is the main cause of horizontal drift with wind.

Similarly, after the peak of the trajectory, the bullet will nose-down slightly, since this position creates the least drag. Again, the drag vector points directly out the tail of the bullet. Drag now has a huge rearward component, and a slight upward component--lift. But only after the peak of the trajectory.

Harold also "ran the math" to show that, at 200 yards, the lift can upwardly displace a bullet about an inch in a 20 mph wind.

Hear's what I understand about this.
Bullets do drift right or left (depending on weather you're in northern or southern hemisphere) and the spin of the bullet does something to is. (I don't remember what I read very well)

This is so minimal as to not make any diference to us, but to the Navy shooting shells 15 miles it could put the shell off something like 100 yards. We, who rarely shoot beyond 1/2 mile would get near nothing in this kind of drift.

Don't worry about this. The thing is that there are so many other variables that we have to worry about that it makes no difference. We've got tiny gusts of wind, the inaccuracy or the rifle, high and low pressure places between us and the target, and a host of other things that much more difference.

True, but so small it can be disregarded.

Spin drift can amount to as much as a full Minute at 1000yds with a 308 target rifle. Comparatively minor considering wind etc. but there nonetheless and some of the best long range shooters do account for it........DJ

Vaugh in his "Rifle Accuracy Facts" gave the first explaination I ever read of why "Wind Drift" is a function of lost velocity
(delay time if you will), and not time of flight.
As the bullet is pointed into the wind (zero angle of attack) part of the drag is a down wind vector. The drag (B.C.) is defined in terms of velocity loss. That is why bulllets drift down
wind. So much B.S. has been writen on the subject. The next
most screwed up concept is the effects of shooting up hill, or down.

Good Luck!

CAS I'll admit it's a little highbrow for the everyday shooter but the benchrest shooters have been observing this for years.Considering the fact that a bullet in flight is rotating about 200,000 rpm a crosswind has an effect on the point of impact.Not only are the shooters watching the direction of their wind flags they are watching their speed also and adjust their hold accordinly.The rotating bullet "grabs" the air and will go high or low depending on the crosswind.The wind flags aren't just used to judge windage but elevation as well.A right twist barrel shoots differently than a left twist barrel.We're only talking about thousanths of an inch here but it is true and it's what wins matches. Truly an art form in itself.

As for me. I'm just happy as a clam if I hit the deer <img src="/ubbthreads/images/graemlins/laugh.gif" alt="" />

284LUVR is exactly right. A rh twist barrel shot in a 3:00 wind will hit higher than a LH twist barrel shot in the same wind. Were the wind to switch to 9:00, the results would reverse. Somewhere in my BR files I have a chart that shows how much the effect is, depending on the angle of the wind.

It is important to clarify, though, that this effect does not cause the bullet to hit "high", just "less low". The bullet is still dropping from the muzzle onward--this effect is nowhere near significant enough to alter the fundamental trajectory. But such things matter in the BR game, where a five-shot five group aggregate of .1800" might win a big match, a .2300" might put you middle of the pack and a .3000" would have you shopping for a new barrel or thinking about golf.

I'll admit to not being as knowledgable about ballistics as many of you. After thinkin' about this a bit, I can believe the rifling marks on a bullet can act like the dimples on a golf ball or stitching on a baseball to produce " bullet spin drift" by way of pressure differential.

Now I have a new explanation for my groups! <img src="/ubbthreads/images/graemlins/grin.gif" alt="" />

--Mike

It's more than that at 200 yards. See the attachment to my previous post.... 1" at 200 yards, in a 20 mph crosswind.

You ought to get one effect while the bullet is climbing, and the opposite effect when it is on the other side of the peak. So there ought to be some way to get your bullet to peak in the right place, so that the effects net out to zero.....

I'm fascinated by the things I find in Harold Vaughn's book. I'm just disappointed that he departed the planet before I could get to know him.

It's the same phenomenon that causes "P" factor in single engine prop planes. It has to be compensted for.

Twin engines spin in opposite directions to cancel out the effect.

Of course, were talking on a much smaller scale, and it's not worth mentioning at the couple hundred yards most of us shoot in. If you were shooting for miles - as in heavy artillery - it has to be taken into consideration.

Denton; I had the honor of talking with Vaughn.His book was so exciting to me that I looked up his tel#. He sounded weak
but was very gracious. He was a real man, and will not be replaced soon. His book should be read by anyone that wonders "what is really going on". So many intuitive answers are wrong,and repeated by the "experts".
Good luck!

The doubters amongst us should take heed to what dj said for he is correct on this subject.

As to the original question, the "sine wave" has nothing to do with "spin drift", but it does exist in virtually all bullets because of gyroscopic precession and the deflections associated with it. In truth it is more of helical path, 3 dimensions being involved. Deep subject, I'm not going to write a book on it here.

Crosswinds cause aerodynamic jump(see Vaughn or McCoy), imbalance in the bullet cases ballistic jump(same). Spin Drift should not be confused with Wind Drift as they are distinct as separate issues. Too, they are not "drift" but a deflection.

You may not want to say a bullet is an airfoil but all rotating cylinders generate lift when subject to a wind component transverse to the axis of rotation. A fired bullet and dropped bullet will NOT strike the ground at precisely the same time for a different reason however, that being the fact that the axis of rotation lags slightly behind the bullets path, thus generating a slight positive angle of attack from an aerodynamic standpoint. Google "Tractability" if you're bored, or see this: http://www.nennstiel-ruprecht.de/bullfly/index.htm#Formulas.

You fellas got a thread going here that real rocket scientists spend their lives on, it won't give you the education in a 10 minute read. Either spend some time on the research or believe the earth is really flat, it's up to you.

DDan, Good link. And thanks Dixie, a good discussion like these two is one of the few things that can make me dig up the old engineering physics books. A little mental exercise is a good thing.................DJ