Bullet Spin...

[steve1 5]

Just when I think I know a lot about guns, something comes up that I have never heard of.

I was watching a movie on military snipers on the History channel yesterday. I've always had an interest in shooting at longer ranges. One of the many variables that affects bullet flight is it's spin. This can cause the bullet to hit left or right of the target at extreme ranges,(depending on the rifling). This is something new to me. Can someone tell me more about this? I'll bet Lou Diamond or John have heard of this.....

[kallend 1,679]

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Just when I think I know a lot about guns, something comes up that I have never heard of.

I was watching a movie on military snipers on the History channel yesterday. I've always had an interest in shooting at longer ranges. One of the many variables that affects bullet flight is it's spin. This can cause the bullet to hit left or right of the target at extreme ranges,(depending on the rifling). This is something new to me. Can someone tell me more about this? I'll bet Lou Diamond or John have heard of this.....

en.wikipedia.org/wiki/External_ballistics#Gyroscopic_drift_.28Spin_drift.29

...

The only sure way to survive a canopy collision is not to have one.

[mnealtx 0]

Yup, gyroscopic drift can push the bullet left/right. Insufficient or excessive spin can affect stability/accuracy. Interesting info, here.

And ALL of it changes with various bullet weights. A barrel that shoots sub-MOA with a 120 grain bullet may only shoot into 2 MOA with a 150 grain bullet.

Ain't it fun?

Mike
I love you, Shannon and Jim.
POPS 9708 , SCR 14706

[steve1 5]

Phew! There's a lot of variables aren't there.... You have to admire anyone who can make those long shots consistently....There's a lot of thinking, practice, and just plain skill with a precision weapon and match ammo....

[rehmwa 2]

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Phew! There's a lot of variables aren't there.... You have to admire anyone who can make those long shots consistently....There's a lot of thinking, practice, and just plain skill with a precision weapon and match ammo....

you ever watch archery, the best will sort through the arrows and only take the best couple for key shots

bullets should be the same

...
Driving is a one dimensional activity - a monkey can do it - being proud of your driving abilities is like being proud of being able to put on pants

[Ron 7]

Coriolis drift is the one that always amazes me.

"No free man shall ever be debarred the use of arms." -- Thomas Jefferson, Thomas Jefferson Papers, 334

[steve1 5]

So this has me wondering. I imagine the rate of twist (of your barrel) would make a difference. But let's say you have an average rifle barrel with a right hand twist. How far will your bullet hit to the right, at say 600 yards on a calm day. Does anyone have a guesstimate?

I've shot groups at 500 yards with little or no wind. That was with a 270 and 300 win. mag. I've noticed a large increase in group size, but I didn't notice a drift to the left or right. So, I'm thinking this drift may not be too much.

I was also thinking of adding a set of target turrets to one of my Leupold scopes. I wish I had some stadia dots or lines on my crosshairs. They could sure help....

I'm not a big fan of long shots on big game. It's just too easy to wound something. But target practice at extreme ranges, would make closer shots easy.

[DrewEckhardt 0]

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you ever watch archery, the best will sort through the arrows and only take the best couple for key shots

bullets should be the same

Arrows get re-used. Fletchings and shafts both get damaged from other arrows ending up in or nearly the same hole

Bullets do not. Bullets and cartridges are the same within manufacturing tolerances.

You pick cartridges with tight tolerances with bullet/powder combinations that produce the least variation with the gun and range in question.

[Rstanley0312 1]

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Phew! There's a lot of variables aren't there.... You have to admire anyone who can make those long shots consistently....There's a lot of thinking, practice, and just plain skill with a precision weapon and match ammo....

I watched that smae special... those shots 1 mile out and 1.5 miles out.... unreal! The other stuff was crazy too.

Life is all about ass....either you're kicking it, kissing it, working it off, or trying to get a piece of it.
Muff Brother #4382 Dudeist Skydiver #000
www.fundraiseadventure.com

[wolfriverjoe 1,371]

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...Bullets do not. Bullets and cartridges are the same within manufacturing tolerances.

You pick cartridges with tight tolerances with bullet/powder combinations that produce the least variation with the gun and range in question.

That's both true and false.

Commercially produced cartridges have certain tolerances. Bullets weights, powder charges, case capacity all can vary. Those tolerances are not large, but can "stack".

And for the most part, rifles and shooters aren't good enough to notice the variation (the errors caused by the shooter and the gun outweigh the errors from the ammo).

But a very good shooter, with a very high quality rifle can benefit from reducing those tolerances as much as possible.

Culling bullets (or using very high quality match grade bullets), measuring powder charges individually to within 1/100 of a grain, culling cases to make sure they are as alike as possible (weighing them and prepping them) all will improve accuracy.

This is of course after finding the most accurate load combination for the gun.

There are a couple guys at my local range that are "accuracy snobs". Start with 10 or 15 different load combinations, work down to the best one, and then make that one as accurate as possible.

3 holes touching at 100 yards is what they are going for, and often accomplish.
But it's a lot of work.

"There are NO situations which do not call for a French Maid outfit." Lucky McSwervy

"~ya don't GET old by being weak & stupid!" - Airtwardo

[rehmwa 2]

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You pick cartridges with tight tolerances with bullet/powder combinations that produce the least variation with the gun and range in question.

this is all I meant - hitting the target isn't about individual skill, as it is about eliminating all possible/controllable sources of ammo

scanning your quiver is the same as picking the most repeatable rounds in this case

...
Driving is a one dimensional activity - a monkey can do it - being proud of your driving abilities is like being proud of being able to put on pants

[billvon 2,476]

>hitting the target isn't about individual skill, as it is about eliminating
>all possible/controllable sources of ammo

That may well be true, but it would sure cut down on the number of people who target shoot.

[LouDiamond 1]

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So this has me wondering. I imagine the rate of twist (of your barrel) would make a difference. But let's say you have an average rifle barrel with a right hand twist. How far will your bullet hit to the right, at say 600 yards on a calm day. Does anyone have a guesstimate?

This depends as it will vary from brand X ammo to brand Y ammo as well as amount of grains used in the ammo and bullet weight. Shooters collect a lot of data in their data books in given circumstances to build a base of reference for particular atmospheric conditions. Most of the data cards you will find are for specific ammo because each has it's own peculiarities and performance envelops. For this reason, serious competition shooters will typically hand load their ammo. So to answer your question there is no way to guesstimate given the info you provided. Typically speaking, you should be able to dial your weapon to 600 yards take a shot and have all of your rounds group within the tolerance of the rifle you are using(this is excluding all human error).

"It's just skydiving..additional drama is not required"
Some people dream about flying, I live my dream
SKYMONKEY PUBLISHING

[millertimeunc 0]

Or just get one of these and be done with it.

http://en.wikipedia.org/wiki/CheyTac_Intervention

The best things in life are dangerous.

[Belgian_Draft 0]

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How far will your bullet hit to the right, at say 600 yards on a calm day. Does anyone have a guesstimate?

S.W.A.G.: An inch and a half, give or take 50%. That should be good for most modern centerfire rifles that would be used at that range.

For 99.999% of shooters it is an interesting yet negligible point. Far more important is that little 2 mph variance in the wind across the muzzle. That has a HUGE influence on the shot compared to spin drift.

HAMMER:
Originally employed as a weapon of war, the hammer nowadays is used as a
kind of divining rod to locate the most expensive parts adjacent the
object we are trying to hit.

[winsor 191]

Quote

Just when I think I know a lot about guns, something comes up that I have never heard of.

I was watching a movie on military snipers on the History channel yesterday. I've always had an interest in shooting at longer ranges. One of the many variables that affects bullet flight is it's spin. This can cause the bullet to hit left or right of the target at extreme ranges,(depending on the rifling). This is something new to me. Can someone tell me more about this? I'll bet Lou Diamond or John have heard of this.....

One reason that long range shooting is not linear is that the bullet tends to retain constant orientation during its flight, but incident air does not. The more the bullet drops, the more it goes sideways through the air.

IIRC, a rifle with a right hand twist will pull to the left at long range and a left hand twist will pull to the right.

Think of a football thrown with a decent amount of spin. When it first leaves the player's hand it is pointed in the direction of travel. By the time it reaches the receiver, however, it is dropping enough that it is going in a direction different than the way it is pointed. The spin at that point tends to initiate drift to the right or left, depending on the way it is spinning.

If you doubt the effect of spin on trajectory, watch the path of a ball thrown by a major-league pitcher. Between the mound and the plate, the ball can wind up going in a completely different direction.

In addition, the farther the bullet travels the more it gets established on a particular drift trajectory - whether it is by virtue of wind or spin. Thus, a correction amounting to 1 MOA at 100 metres may show up as a 3 MOA deflection at 500 metres. Put another way, conditions that cause 1" of drift at 100m could result in 15" of drift at 500m.

In any event, the physics of long-range marksmanship are not quite as simplistic as one might imagine.


BSBD,

Winsor

[JohnRich 4]

The long range shooters I shoot with don't really worry about spin drift. When you first work up an ammo load for a rifle, you zero the sights with that. So the spin drift is built into the zero. All you need to know is that on a no-wind day at 1,000-yards you leave the windage knob on zero, and raise your elevation for the distance. Bang! You're on target.

Change your load, and the zero will change with it. Take notes, and dial it back in the next time you shoot that load.

There are so many other things that are larger factors, that spin drift doesn't really count for much.

A tiny little 5 mph crosswind at 1,000-yards will put about 30" of sideways drift on a .308 bullet. That's the kind of thing I worry about.

I shot my Swiss K31 in a 600-yard match last weekend. Look at the attached image, and see how much my elevation changes for this rifle, simply depending upon which of two types of ammo I use. That will screw me up far more than any spin drift. Three MOA difference at 600 yards - 18 inches!

[AggieDave 6]

Very few people can out shoot their gun.

Well, let me quantify that.

Very few people can out shoot a quality firearm. Most pistol shooters won't out shoot their Glock, for instance.

Trigger control and breathing do more for most people in terms of accuracy, then having the most costly equipment that will shoot sub MOA every time.

As for the OP, that was an outstanding show, huh?

--"When I die, may I be surrounded by scattered chrome and burning gasoline."

[kallend 1,679]

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Coriolis drift is the one that always amazes me.

Yeah, but that's due to the spin of the Earth.

...

The only sure way to survive a canopy collision is not to have one.

[Gene03 0]

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Coriolis drift is the one that always amazes me.

No kidding, what did the Germans have to lead Paris?
20 some miles?

“The only fool bigger than the person who knows it all is the person who argues with him.

Stanislaw Jerzy Lec quotes (Polish writer, poet and satirist 1906-1966)

[rhaig 0]

for sale: used French WWII rifle. Never fired. Dropped once.

--
Rob

[Amazon 7]

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for sale: used French WWII rifle. Never fired. Dropped once.

ALthough that is the usual joke surrounding the Lebel Rifles... MANY of those same rifles had been used by several dead French soldiers from the trenches of WWI. You will find a lot of them with pretty lousy barrels. Do you have any idea how many young men died with those rifles?

[Belgian_Draft 0]

Since Monaco has no standing army, they have an agreement with France for military services. If Monaco is ever attacked, the French will surrender for them.

HAMMER:
Originally employed as a weapon of war, the hammer nowadays is used as a
kind of divining rod to locate the most expensive parts adjacent the
object we are trying to hit.

[Gene03 0]

Quote

Quote

for sale: used French WWII rifle. Never fired. Dropped once.

ALthough that is the usual joke surrounding the Lebel Rifles... MANY of those same rifles had been used by several dead French soldiers from the trenches of WWI. You will find a lot of them with pretty lousy barrels. Do you have any idea how many young men died with those rifles?

Oh crap, here we go with the frog jokes.

I take it that a lot of infantrymen used those rifles successfully after the original owners dropped them?

“The only fool bigger than the person who knows it all is the person who argues with him.

Stanislaw Jerzy Lec quotes (Polish writer, poet and satirist 1906-1966)

[wolfriverjoe 1,371]

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Quote

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for sale: used French WWII rifle. Never fired. Dropped once.

ALthough that is the usual joke surrounding the Lebel Rifles... MANY of those same rifles had been used by several dead French soldiers from the trenches of WWI. You will find a lot of them with pretty lousy barrels. Do you have any idea how many young men died with those rifles?

Oh crap, here we go with the frog jokes.

I take it that a lot of infantrymen used those rifles successfully after the original owners dropped them?

No, the original owners were slaughtered with them in their hands after their commanders sent them on an impossible suicide mission. Somewhere in the neighborhood of 100,000 of them is a few days during one disasterous offensive.

Wiki Clicky

"There are NO situations which do not call for a French Maid outfit." Lucky McSwervy

"~ya don't GET old by being weak & stupid!" - Airtwardo