Home Forums Hunting & Shooting Hunting Rifles Bullet spin causes float?

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="" />

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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!)

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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