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starik
12-27-2007, 12:29 PM
What makes a barrel shoot better in the wind than other barrels?
Is it the twist rate?, The number of grooves?, The length? the chamber? the muzzle?. Can a barrel which shoots great in perfect conditiones shoot bad in windy day? your opinions please.
Guy.

Joe Haller
12-27-2007, 01:35 PM
The variable I think most important is the ability of the bullet to stabilize quickly after it leaves the barrel. The average bullet will scribe a corkscrew path for some distance after it leaves the muzzle. Then if the barrel has the right twist for the weight of the bullet, it will start to spin true and “go to sleep”. The longer the bullet “screws” around, the more the wind will affect it’s path.

Like a child’s top that “hums” when it is stable, the bullet is suppose to go to sleep and hum soon after it leaves the barrel. The sooner the better.

That hummer barrel we all dream of having, will put those little babies to sleep as soon as they leave the barrel.

What makes a barrel hum? My guess is, it’s a combination of things. With the right mix, and the right vibratons, ya got a hummer. They are rare, and if you get one, you are lucky.

Joe Haller :-)

BigMacky
12-27-2007, 03:37 PM
Very Interesting Joe .... have there been any estimates or measurements taken as to how far the average bullet corkscrews before stabilizing (like how mant feet?)

Fred

tim
12-27-2007, 03:57 PM
What makes a barrel shoot better in the wind than other barrels?
Is it the twist rate?, The number of grooves?, The length? the chamber? the muzzle?. Can a barrel which shoots great in perfect conditiones shoot bad in windy day? your opinions please.
Guy.

Lots, and I mean lots of very good barrels are not good wind barrels. Many very good smiths will tell you that #'s of lands, depth, width, taper of bore will all conribute.

Kathy
12-27-2007, 05:23 PM
Friend Starik:

I'm posting on your thread only because I see this is your first post, and, you have asked a very interesting question.

Good luck.

Your friend, Bill Calfee

Dave Shattuck
12-27-2007, 05:59 PM
I agree with Joe 100%, and I know that it may seem like I am drifting away from the topic, but what I am about to say is very pertinent when it comes to all matters concerning precision accuracy. What I will ad is this; if you have a truly great combination of everything else except for one thing, you may never know the true potential of just how good everything else really may be. In other words: if you have the proper barrel length, number of groves, grove depth, rate of spin, bore diameter in relation to lands diameter, chamber cut and everything else is dead on, plus the lot number of your bullets is perfect for your gun, if for some reason some minor little thing is off, like the torque on the action screws is too loose or tight, or the barrel is vibrating at an inconsistant rate while the bullet exits the muzzle, you may never actually realize just how good a combination you really do have.

Oh, you may be able to put together some awesome scores under certain conditions, but everything will soon fall apart under those not-so-certain of conditions.

As Joe said: in the perfect scenario you want your bullet to "go to sleep" just as soon as possible after it leaves the barrel, and if possible, immediately upon its exit from the bore.

There's no sure cure for how much of which or what will be the ultimate answer to achieving your goal of precision accuracy. You will just have to shoot and shoot ...and practice, practice, practice to find out the answers. And when at practice, don't just pull up to the bench and blast away. Analyze everything; how the rest sits on the bench, how the target hangs on its backer, how your windflags are placed to give you the proper readings for the conditions, are you comfortable while sitting at the bench over long periods of time, how smoothly does your gun ride the bags, how much pressure, or lack there of, you are placing the butt pad ....shot after shot. Everything, because nothing is irrelevant when it comes to benchrest shooting! It is only after a perfect balance has been achieved that you will start to reap the rewards of seeing perfection on the target time after time after time.

And yes, this does have something to do with to how well a gun will shoot the wind!

GordonE
12-27-2007, 06:39 PM
Starik
The best wind shooting barrels are the ones that are tuned the best. They will also shoot in the calm. Any rimfire barrel no matter how it shoots in the wind, It will shoot better tuned. The centerfire guys are finding this out also.

Kent Owens
12-27-2007, 07:01 PM
I agree with GordonE, assuming it's a quality barrel on a BR rifle shooting quality ammo, quality scope, great bedding, etc., tune is everything, but sometimes real hard to find.

ThaiBoxer
12-27-2007, 08:33 PM
Now, then. What is "tune"?

ThaiBoxer
12-27-2007, 08:34 PM
Beside you shower-singing voice, I mean... ;)

Kent Owens
12-27-2007, 08:40 PM
Ben,
I'm replying to your post because I see it was your 696th post. That was a very interesting question. Thank for asking it. Happy New Year! Good luck to you.

On a serious note, it's like what Joe said, or at least I think so.

"The variable I think most important is the ability of the bullet to stabilize quickly after it leaves the barrel. The average bullet will scribe a corkscrew path for some distance after it leaves the muzzle. Then if the barrel has the right twist for the weight of the bullet, it will start to spin true and “go to sleep”. The longer the bullet “screws” around, the more the wind will affect it’s path.

Like a child’s top that “hums” when it is stable, the bullet is suppose to go to sleep and hum soon after it leaves the barrel. The sooner the better.

That hummer barrel we all dream of having, will put those little babies to sleep as soon as they leave the barrel.

What makes a barrel hum? My guess is, it’s a combination of things. With the right mix, and the right vibratons, ya got a hummer. They are rare, and if you get one, you are lucky."

Joe Haller :-)

Bill Wynne
12-27-2007, 10:01 PM
What makes a barrel shoot better in the wind than other barrels?
Is it the twist rate?, The number of grooves?, The length? the chamber? the muzzle?. Can a barrel which shoots great in perfect conditiones shoot bad in windy day? your opinions please.
Guy.

Starik,

That may be that best question of '07. Joe's answer may be the best that you will get. Ben's question about tune may have been the second best question.

I am going to take a guess at your last question. Yes, a barrel that shoots great in perfect conditions can shoot bad on a windy day. But then, they all shoot better under perfect conditions.

starik
12-28-2007, 12:03 AM
The question is: If there is a better twist rate for a 0.22 or special muzzle form which will let the bullet go to sleep early, or is it only tuning?
I am a prone shooter dealing a lot with windy conditiones in internatinal competitiones, and I can't put a heavy weight at muzzle as a tuner.
Is there any thing I can do exept the heavy tuner?
Guy.

ThaiBoxer
12-28-2007, 12:09 AM
I keep hearing about getting a killer hummer in a barrel for only $300, but all I find is some greasy gunsmith with a piece of steel.

I ask you, "Where is the justice in that?"

Joe Haller
12-28-2007, 12:32 AM
Fred (BigMacky) asked a question about ". . . measurements taken as to how far the average bullet corkscrews before stabilizing (like how many feet?)

Fred: I don’t have that information, but my guess would be that it would be anywhere from a fraction of an inch to “never”.

My first information about the corkscrew bullet came from a smallbore friend in Wheaton Illinois back in 1959. I was a member of the Wheaton Rifle Club at the time. Wheaton is one of the Western Chicago Suburbs. There was a boat load of Master Smallbore Prone and 4 Position Shooters in that club. I learned a lot from them.

One nice summer evening I was practicing with one of these Masters. I watched through my spotting scope as he punched very small 10 shot groups into the X ring of a 100 yard target. When we were through, I noticed he had tossed some 50 yard A-23 targets in the trash. I looked at them, and the 5 shot groups were terrible! They would have measured more than an inch and a half across. I said: “Bob, what gun did you shoot these with". He said: “Same rifle: The bullets are not stabilizing until they get out beyond 50 yards”. He told me the rifle was a Winchester M-52B with a custom barrel put on by Mr. Womak down in Louisiana. I don’t recall his saying what the twist rate was.

The second time I ran across the “cork screw” was in a book. Back in 1981 my dear wife Mavis got me a book for Christmas called, “The Bullets Flight”, by Dr. Franklin Mann. Dr. Mann had done a lot of research on external ballistics in the 1890s and early 1900s. After you read his book you KNOW that Dr. Mann was a genius with a special insight into physics. In 1907 he set up paper screens one foot apart out to 100 yards and plotted the path of the bullets he shot from his machine rest. Seems most of his tests were done with a Pope barreled 32-47 with 187 grain bullets. He was a friend of Harry Pope.

I have read a lot of articles in Precision Shooting since 1956. Don’t recall reading anything about this kind of a test being duplicated. But: When I was shooting High Power Metallic Silhouette back 30 years ago at Camp Grayling, I watched the corkscrewing vapor trails of 168 grain Sierras reaching out to 500 meters.

Joe Haller - Mr. Frosty

Patriot
12-28-2007, 12:36 AM
The question is: If there is a better twist rate for a 0.22 or special muzzle form which will let the bullet go to sleep early, or is it only tuning?
I am a prone shooter dealing a lot with windy conditiones in internatinal competitiones, and I can't put a heavy weight at muzzle as a tuner.
Is there any thing I can do exept the heavy tuner?
Guy.

I'm not an expert, but I've read that a barrel with a slight choke at the muzzle will do much better in the wind (and in calm too). It probably makes sense given that if the bullet is not yawing it should generate less induced drag, reducing drift.

Mark

John Kielly
12-28-2007, 02:57 AM
To tell the truth, I'm not even sure that speed of going to sleep isn't just a function of quality precision gunsmithing, particularly chambering tolerances & quality assembly of handloads.

I shoot mainly over 1000 to 1200 yards distance (Brit match rifle) & that's with a setup restricted to a standard .308 Winchester chambering (throat length whatever you like) & a barrel weighing no more than 2.5 kg. That means that the 32" tubes I shoot are Kreiger 1:10 twist light Palma profile running to 32 inches. When I was load testing 210 grain Berger VLDs with my last barrel but one (looking for spreads under 20 fps & SDs under 8), I found that the most promising loads were grouping an even MOA - what I'd been told to expect from the big pills that go to sleep slowly. However, when I dropped on my barrel tuner weighing around 2 ounces & tweaked it, I managed to pull those groups down to something a tad more than ¼ MOA, maybe .3+. That's 10 shot groups.

My gunsmith, John Giles, has reasonable qualifications & I've been loading since the late 60s & occasionally even listen to some young whippersnappers , so I reckon that I do have a good rig & can feed it pretty well. Maybe bullets go to sleep quicker if they start off down the bore square & concentric.

However, the barrel that I most recall as being great at bucking wind was back in the days I shot target rifle with iron sights. I could bench that rifle at 300 yards on the local SSAA range & get 2 inch groups at 300 yards & I was invulnerable with it on the open range, except when it came time to clean it. This factory barrel for an Omark target rifle was built & quality controlled by a pack of gorillas. The reamer had chattered down the bore & described a corkscrew that you could see with the naked eye. As a result, the rifling seemed to be deeper in places than it was in others, all of which made the coppering pattern novel to say the least & protracted use of Sweets a necessity.

Now, we were shooting on 2 MOA + bullseyes, so there wasn't all that much difficulty in holding elevation. ON the other hand, if I was shooting a rifle that for it's own perverse locic shot Aussie military 144 NATO ammunition consistently under 1 MOA when most rifles of the day were holding worse than twice that, of course I was liable to have a bit up my sleeve when the wind blew.

Maybe that's what the close shooters are - just tighter shooting barrels. Would it be all that easy to recognize a real hummer when we see one, when we're shooting such incredible groups with about any gun these days?

GordonE
12-28-2007, 05:20 AM
Tune
Yesterday we shot 4 different 10.5 guns and 3 sporters. It was 32deg. a lite rain. Which meant the wind flags froze and were usless. a slight switchy breeze. We shot several different lots of ammo. The guns that were tuned the best shot the best. The best ammo shot the best in all guns. This showed up the most when the wind speed changed. as the bullets in a couple guns would move twice as far. I still can't believe how well all the guns shot yesterday.

I made screw in weights out of aluminum and steel for a Harrels tuner to be able to add 1oz. at a time up to a pound. It works much better than adding weel weights. With weel weights on one side and you move it it dosen't seem to work with it out of balance. When you get the right amount of weight you have a lot bigger window of movement on the tuner.

Øyvind
12-28-2007, 05:41 AM
I have seen the rifle You are using and I could think of several ways to make room for the tuner on it. That we can discuss in person next month i Finland.

Øyvind :-)

starik
12-28-2007, 07:12 AM
Hi Oyvind,
The problem is only with the weight of the tuner, I know it's no problem to fix it.Too heavy weight will distroy my hold for the long run.
I didn't get any answer to my question yet, regarding twist rate, muzzle form, number of grooves, etc.If a barrel shoots great indoors, it must be perfectly tuned before, so why two barrels which are tuned perfectly will shoot different in the wind?
Guy.

GordonE
12-28-2007, 07:31 AM
Starik
If a barrel maker could figure that out. He would be the only one in business.

Beau
12-28-2007, 07:37 AM
Given two barrels that are in the same exact tune, which is unlikely, but one shoots better in the wind, it's probably velocity, which may be a function of barrel length. But there goes the "same exact tune" theory, because they were not tuned the same to begin with.

The thing I'm not understanding here is the "corkscrew" theory. If I read one post correctly, bullets may "corkscrew" and produce crappy groups out to 50 yards but, within the same flight, get on path and produce great groups out to 100 yards. It would be like a drunk driver telling a cop "I can't walk ten feet straight, but after that, I'll be right on path." Of course, he has to find the path first and the drunk has a brain, maybe not much of one, but still. I'd like to hear how that "corkscrew" works.

brad541thb
12-28-2007, 08:01 AM
If a gun shoots single hole groups at 25yds, it ought to do the same or be capable of the same at 50yds. I believe what Mr. Haller said and he is on the right path to what he is saying. I believe that a pefectly cut barrel which we all strive to get that seems to be a hummer of a barrel will stabilize a perfectly concentric bullet before the bullet leaves the barrel. Some barrels just seem to shoot more ammo better than other barrels. Why that is I believe is in the precision of just how close to perfect it was cut and lapped. Like Joe said, a hummer of a barrel is extremely hard to find. I can tell you that Joe Besche's Douglas barrel was probably the most hummerest :D barrel I have actually ever witnessed to shoot day in and day out. That barrel was what I call a true barn burner. They don't get much better than that.


Brad

Joe Friedrich
12-28-2007, 12:21 PM
How many of us folks really know our rifles, given that the barrel we are using is consistent or uniform from one end to the other ( steel, straightness, chamber, lands, grooves, twist, etc.), then there's tuner weight and setting, and selection of ammo.

Then there are those that know the art of lapping a barrel.

Joe

Fred K
12-28-2007, 12:25 PM
Have to agree with Beau.

If it don't shoot good groups at 50 yds it will not shoot good groups at 100 yds.
Groups get larger as a fuction of distance.
Fred K

Fred J
12-28-2007, 01:39 PM
I had a 30" Douglas, that would shoot 3/4 groups at 50 yrds, but at 100, I could cover 10 with a dime off the bench. Sure wish I still had it.

pacecil
12-28-2007, 02:50 PM
The idea a gun will shoot smaller groups at 100 yards than it will at 50 yards is simply wrong unless you are measuring the groups in minutes of angle instead of inches. Shooters (Fred J) rarely if ever are shooting through two targets, one at 50 and one at 100 yards, to confirm what they "imagine" occurs.

Bullets leaving the barrel always have some yaw in their flight. In a 22 rimfire the degree of yaw can be reduced at a point about 10 yards up to 60 yards from the muzzle (as Beau pointed out). When this angle of yaw has dropped to only a fraction of a degree the bullet has stabilized or gone to "sleep". Whether the yaw has dropped early in the flight or later has some slight effect on the wind effect on the bullet. Properties of the barrel and the effect of the barrel on the bullet will influence the amount of yaw imparted to the bullet as it leaves the muzzle and thus some barrels may show more "wind effect" than others. Considering the tuners effect is mostly in the vertical it also has practically no effect on the flight of a bullet to resist the wind force. The total "reduced wind effect" is very small in a high quality bench rest barrel, and would take many many groups in constant conditions to confirm - it is thus also "imagined" in most cases.

Then there is that question: "Can a barrel that shoots great in calm conditions, shoot bad on a windy day?.....Duh!

GordonE
12-28-2007, 03:28 PM
Pacecil
I am confused. (Which is normal) You say that a tuner will influence vertical but won't have much influence on the flight of the bullet. Then why can you tune a barrel to a to a lot less vertical when you have a change in wind velocity.

pacecil
12-28-2007, 04:03 PM
To Gordon E,
I'm not sure what you are asking. Are you saying you can make a tuner adjustment while the wind is changing and reduce the vertical group size compared to what it would have been before the wind change?

Fred K
12-28-2007, 04:05 PM
I have found you can tune for the best vertical or horizontal POI. In all my test I find the two don't occur at the same tuner setting. Tested on more than one rifle, barrel and tuner. Anyone else noted this ?
Fred K

GordonE
12-28-2007, 04:14 PM
Pacecil
No what i am saying is if the barrel is tuned. A change in wind velocity won't move the bullet as far as a as if it isn't tuned.
Fred
I worry a lot more about vertical than Horizontal. Never had much luck with 2 tuner settings.

Bill Wynne
12-28-2007, 04:15 PM
What makes a (one) barrel shoot better in the wind than other barrels?

This was the hardest of your questions and the most interesting. I feel that we are getting away from it.

The way I see it is that no one knows. Gunsmithing is a craft not a science. True, there are some elements of physics that play a very large part and these should be understood but, by and large, it is a craft to be learned.

DonMatzeder
12-28-2007, 04:16 PM
Tuner changes seem to change POI for me. Also, smallest group setting in a tunnel is not the best setting for shooting in the wind. I'm not a theorist, just a shooter. I don't know why.

vicvanb
12-28-2007, 05:06 PM
What makes a barrel shoot better in the wind than other barrels?
Is it the twist rate?, The number of grooves?, The length? the chamber? the muzzle?. Can a barrel which shoots great in perfect conditiones shoot bad in windy day? your opinions please.
Guy.

Are we certain that one barrel DOES shoot better in the wind than other barrels?

I know the legend of the "hummer" barrel is widely accepted but has it ever been proven?

pacecil
12-28-2007, 05:14 PM
Okay, it's time to bring up something none of you want to hear!

There was an article in Precision Shooting about 15 years ago where an "expert", a scientist, an engineer, a benchrest shooter - he was all these - used some math and a computer to determine what information you could get out of groups. Basically he determined that you have about a 50% probability, or a 50/50 chance, of being right when you shoot a group and decide if some change you've made has caused the group to be larger or smaller. In other words when you think a barrel shoots better in the wind than another one and you shoot a group to decide this you only have about a 50/50 chance of being right. If you shoot a group in the wind with a tuned barrel you have a 50/50 chance the group will be smaller than it would have been with an untuned barrel.(You also have a 50/50 chance it will be LARGER!) He applied groups of 3 to 20 shots and up to 25 groups (easy to do in a computer) and probabilities change somewhat but in the group sizes and number of groups most of us use the bottom line is we only have about a 50/50 chance that what we read from the group dimension will be right!

Bill Myers
12-28-2007, 05:49 PM
Starik,Sometime in mid February,you will answer your own Question. BILL

Tom C.
12-28-2007, 06:34 PM
does anyone have a spare wind tunnel
i need one for testing. wonder how much this
is going to cost me?

DonMatzeder
12-28-2007, 07:17 PM
You can shoot for free in mine but the ammo is on you.

Tom C.
12-28-2007, 07:36 PM
argh, another expense does it ever end?

Joe Haller
12-28-2007, 10:25 PM
I suspect that the shooters who come close to proving the Hummer Legion, are the ones who buy 6 or a dozen barrels each year, test them all, and then win matches with the one that is, or comes close to being a Hummer.

Joe Haller

starik
12-29-2007, 12:52 AM
I understand that nobody realy knows the answer to the question.
I still think that twist rate must be a factor in the sensibility of a bullet to the wind. Any one ever tried it? What about number of grooves? do you think it can make the difference? If I have 2 lots which shoots good from my barrel, I will shoot the slower one on a windy day.
Guy.

Beau
12-29-2007, 01:18 AM
I think the answer to your original question is "all of the above". I also think twist rate could be a factor. There are several who have tried a 17 twist as compared to the traditional 16 twist, and I'm sure there are those who still use them. I had a shorter barreled 17 twist that shot super in the calm but was nuts in the wind. I need to clarify that the barrel was probably consistent even in the wind, it was just that I could not control it in a windy condition. I have heard others say the same, but also have to point out that some of the great shooting Suhls were/are 18 and even 19 twist. For the most part, barrel length simply affects velocity and little else. I like a longer barrel for that reason, it produces slower velocities and I can control that better in the wind.

Can a barrel that shoots great in calm shoot crappy in the wind? Probably the real answer is no, it will still be consistent. However, many factors including ammo velocities etc. can cause differences. On top of that most of us subscribe to the thinking that "it can't be me, so it must be the barrel (ammo, action, tuner, phase of the moon, whatever).

Øyvind
12-29-2007, 04:33 AM
You have just given an answer about the velocity, Guy :-) Different barrels produce different velocities and different yaws due to the fact of the interior of each barrel.Some think regular twist is the answer yet others think gain twist is the thing. Anschütz produce barrels with a slight gain, and have tried most different twists I think.These days I believe they use 450mm breech to about 430/420mm muzzle twist.They claim their barrels are uniform inside to within 1000's of a mm. I have seen "bore" transcripts of some produced earlier years and the ones they are producing today.It is impressive.But, why do they all shoot different? They also shoot different in the two ranges they have at the factory. One "cold" and one warm temperature wise.This means of course that the "fingerprint" of the barrels change due to temperature impact plus also the flight of the bullet to the target. Does this also have an impact on the yaw? I think so. Good barrels shoot better than bad barrels and beyond that I think it is of little use to us. My Lilja, Border and Anschütz barrels are all shooting fine, but with different ammo and in different temperatures. Try shooting in the wind with a Noptel opto electronic device a check your ammo.

1813benny
12-29-2007, 09:53 AM
Throwing something else into the mix....

Is it the "rifle" (as a system) what is shooting better in the wind, or is it just the shooter, via an external influence (i.e. wind) just working harder on reading conditions & shot execution?

Wilbur
12-29-2007, 01:21 PM
...theory............... I'd like to hear how that "corkscrew" works.

Not sure if it's a theory or what but certainly sure I don't understand it . I have, however, observed behaviour that supports the concept.

Leaving out the physics, the bullet exits the barrel in a corkscrew path that "screws" about and converges to a "line". Once converged, the bullet remains on the line for the remainder of flight. The characteristic is larger to smaller groups as the distance increases.

Joe Haller
12-29-2007, 01:58 PM
One of my thoughts has been: Deep hole drilling can only produce a perfect hole, on center from end to end, in a small percentage of barrels.

From that, I "think" maybe those are the barrels that, if chambered right, with the tight end up front, and bedded right and tuned right, and permitted to recoil the same from shot to shot: Will Hummmmm when you feed them ammo they like.

Joe Haller (Mr. Frosty)

ThaiBoxer
12-29-2007, 03:24 PM
I would WAG that the centripedal forces that make for gyroscopic effect might explain the corkscrew. As for the perfectly centered gundrilled holes, I thought the smiths centered the blanks on each end, and turned down the OD based on the bore.

Shots in the dark,

Ben

gordon gauge
12-29-2007, 03:31 PM
Seems like a bullet that is corkscrewing or yawing would poke a bigger hole than one that has gone to sleep. If you are wondering where in the bullets trajectory it is going to sleep, perhaps you could place something, something better than paper which tends to tear, at increasing distances and measure the holes until they get smaller.......

Hey Kent, that was funny! Havent blown coffee out my nose in quite a while. http://emoticons4u.com/happy/1002.gif

Wilbur
12-29-2007, 04:53 PM
Corkscrew and yaw ain't the same. Yaw is wobblin' and corkscrew is....corkscrewin'.

I can say that cause y'all can't see 'em either. Far as I know it's the truth.

Bill Wynne
12-29-2007, 05:36 PM
I believe in the term corkscrewin'. Kinda like squirrelin'. I believe that it is an effect not unlike a curve in baseball caused by the spinning of the bullet through the air. The bullet appears to go up and to the right and then down inscribing a 1/2 circle arch as it approaches the target. Under the right conditions it can be seen with the eye through a scope. The up and down are surely the trajectory but the right direction movement must be the curve ball effect.

Well, maybe my barrel just "squirrels" off to the right.:)

I just wish I had a hummer barrel on my rifle. I don't care what the bore is like, bent or squirrely or whatever.

B. Harvey
12-29-2007, 07:45 PM
With my current barrel, a 3 groove 18 twist Benchmark, I have seen the corkscrewing on alot of occasions, even at the Barn.

I shot another rifle at the Barn on the same day that was a 16 twist and the bullets appeared to go up and then down into the bull. No noticeable corkscrewing with this rifle.

My scores were ALOT higher with the 16 twist and accuracy was of course, much better.

You would think that the slower twist would develop less of a corkscrew path, but there seems to be more to it. Maybe what we are seeing is actually bullet instability.

ThaiBoxer
12-29-2007, 09:13 PM
Corkscrewing related to this?

http://upload.wikimedia.org/wikipedia/commons/thumb/8/82/Gyroscope_precession.gif/180px-Gyroscope_precession.gif

Fred K
12-29-2007, 10:08 PM
Bulletts never go up after leaving the crown. Put another way they don't go above the bore sight line. They start dropping right away.
Fred K

_Shorty
12-30-2007, 01:18 AM
They begin accelerating towards the ground right away, but that's not the same thing as dropping. They only start dropping right away if the boreline is parallel to the ground. They rise for a certain amount of time before they begin dropping. You would have to be shooting at a very short distance in order to have your bullets start dropping immediately. The majority of targets and distances we'll be shooting at require us to aim the bore upwards so that the bullet will hit where we want it to, otherwise it would hit well below where we'd like. That, and the sightline is higher than the boreline, so the boreline needs to be angled upwards to meet the sightline, too. Gravity's acceleration begins immediately, yes, but we are still giving it some amount of speed in the upward direction, so they're not dropping right away.

Beau
12-30-2007, 01:36 AM
In regard to the ballistic trajectory the bullet may go up relative to the ground, but as Fred says, they do not go above the bore sight line. This may be generally speaking and assuming a vacuum as there could be some force of air that actually would move it above the bore sight line, but you are correct in that it begins accelerating towards the ground immediately. So it may move up but at the same time begins to drop. Drop is just a matter of semantics. I understand what Fred is saying and I agree with him for what it's worth.

_Shorty
12-30-2007, 01:42 AM
Dropping is moving towards the ground.

Accelerating downwards is not the same as dropping. If you throw a rock as hard as you can straight up, it is accelerating downwards the instant it leaves your hand. But it is not *dropping* until after it stops moving upwards at its peak height during its trip. Right after it reaches that peak it will begin moving downward, and that is when it is dropping.

I don't understand why you say it will never be above the sightline, because it most certainly can. All depends on the distance you're shooting.

Wilbur
12-30-2007, 02:14 AM
The bore sight line - not the line of sight.

_Shorty
12-30-2007, 02:20 AM
Gotcha.

Bill Wynne
12-30-2007, 08:08 AM
The bore sight line - not the line of sight.

That's what I meant.

Fred K
12-30-2007, 09:22 AM
On Acceleration
There is very little bulllet acceleration toward the ground from a perfectly level bore.

Example; Level Bore.
Let say you dropped a bullet at the muzzle of a level bore. The acceleration to the ground would be the same as the bullet fired from the level bore. If you could drop and fire the bullet from the crown at the same time they would both hit the ground at the same time. This of course would have to be over level ground.
Fred K

gordon gauge
12-30-2007, 02:39 PM
The bullet begins dropping and deaccelerating the instant that it clears the bore of the barrel. The reason it appears to rise is because you are pointing the barrel up. It would need some other means of propulsion in order to rise. Has somebody taken too many nips at the Eggnog.......http://emoticons4u.com/crazy/1139.gif ...just kiddin'.


p.s. Fred, what you said sounds correct except that there is no acceleration

Fred K
12-30-2007, 03:12 PM
GG, falling bodies accelerate until they are stabilize by air resistance.
Was it Newton that prove this, not sure, think it was him.

Fred K

Beau
12-30-2007, 03:13 PM
Acceleration towards the ground is 9.32 meters per second square assuming no resistance.

MikeSmith
12-30-2007, 03:13 PM
Corkscrewing related to this?

http://upload.wikimedia.org/wikipedia/commons/thumb/8/82/Gyroscope_precession.gif/180px-Gyroscope_precession.gif

Ben,

I think that is precession. My Milankovitch Cyclicity is a little rusty. I think what they mean by corkscewing would be moving around an axis as opposed to a tilted axis of movement. Clear as mud, right?

Fred K
12-30-2007, 03:25 PM
Beau, Think that is true in a vacuum. In air the shape is the restrictor.
At my age I'm forgetting many things.
Fred K

ThaiBoxer
12-30-2007, 03:31 PM
Mike, yes it is precession. I don't have the training to understand it. Whether the described "bullet corkscrewing" is actually corkscrewing or not, I have no idea. If I posit that precession is what occurs, I would expect observers to describe it as corkscrewing, since the rotation must be pretty slight.

Another shot in the dark,

Ben

Joe Haller
12-30-2007, 05:23 PM
The math involved in Torque-free and Torque-induced gyroscopic precssion makes my head spin.

This corkscrew is easier for me to understand. I have one like it in a kitchen drawer. I was told it is a "French" corkscrew.

Joe :-)

http://img.photobucket.com/albums/v186/Joe_Haller/Instructions/FrenchCorkscrew.jpg

_Shorty
12-31-2007, 01:50 AM
Gravity's acceleration is 9.81m/s/s (http://en.wikipedia.org/wiki/Gravity), and yes, air resistance plays a factor. But this remains the same regardless of angle of fire. I wouldn't call it a small amount, not sure why you consider it to be.

Beau
12-31-2007, 06:42 AM
Hey I got close. Not bad for a guess. Anyway, it's constant, so you couldn't say it's small or large. I think he was indicating that the downward velocity due to gravity would be relatively small, which is generally true. Now, why does it matter?

gordon gauge
12-31-2007, 05:59 PM
....it matters 'cause I won't have anything to do with anything thats French. http://emoticons4u.com/dressed/bek073.gif wee-wee

And I was talking about accelleration towards the target, not the ground, so I see what you mean I think, eh? Thx, GG

stash247
01-05-2008, 06:15 AM
A bullet, out of balance at the nose end, will continue to yaw, further and further from the line of sight, as range increases; one with an inbalance, at the tail, will 'settle down' as range increases, due to the effects of air friction.
But a lousy 'crown', at the muzzle, will do the same thing; ie, shoot worse groups at 50, than 100, or further, if one is reading simply moa; a bad crown 'tips' the bullet, but a good bullet will 'settle down'.
Now, this question was asked, in original form, about rimfire rifles, ammo for which we have little control, except the 'buying decision'.
That said, the bullets are swaged, from lead wire, in precision dies, which should allow for essentially no voids, or incusions, so balance shoud be a constant, for the bullet.
Stuff it into an oversized chamber, or a chamber with a 'generous' throat, and we may well launch it, sorta sidewise, and create the imbalance, by cutting lead, in the bore, and likely,with an 'off center' bullet, range will only make it worse!
I order, inspect, and use only barrels to my dimension; my reamers are ordered to my specs, and anything outside those numbers, is sent back.
Frequently, my rifles show returns on my investment; a rewarding, gratifying, thing, what mkes it all worthwhile!
Today, most of my bigger bore, 'cast bullet' rifles, shoot nothing but bullets dropped from 'nose pour' molds, to insure that if imbalance exists, it will be 'out front', to ensure the best possible acuracy, at all ranges.
A forty caliber Sharps, one that I like a lot, wil seldom shoot less than 1 1/2 inches, at 100, but less, at 200, and by 300,we gotta swear to 1 1/2 inch groups, and predictably constant, when I do my part;a 420 gr bullet, about 1800 fps, that absolutely 'goes to sleep' before 150, and hits like a hammer; it's over an inch and a quarter long!
This is a rifle that does not know wind, only hold, but is barreled in a relatively 'fast' twist, for the caliber.
All leading up to a highly controversial term, and subject.
If for a moment, I assume a bullet to be a symmetric, balanced, monolithic cylinder, how, by rotation, can I 'Overstabilise' it?
With good bullets, this is impossible; only if there exists a bullet, or contrenciity, problem, is 'decreased' accuracy, possible.
My 'wind' barrel carries a Shilen pedigree, and a 14" twist, for a .22 LR, a bit 'fast', by conventional wisdom, yet it shoots as well, in wind, as in still air, given ammo it 'likes', the 16",and 17" barrels, maybe shoot a little tighter, in still air, but "lose it",in the wind, by comparison.
These are as close to 'identical items',in bore, choke taper, and profile, as it gets; all use the same fore end, etc, on a 44 1/2 Stevens Chassis, tuned for accuracy, and for the answer to exactly this question; wht is the optimal rifling twist, for a .22LR, match quality, cartridge?
Yet, to date, I have yet to find a better 'wind' barrel, than the 14" Shilen!
The 17" is awesome, in still conditions, but as the wind rises, it goes all to hell, for accuracy, by my standards, at the least, while the 14 loves windy weather!
A 12" twist .308 seems to support this conclusion, as it seems to shoot as well in wind as , or better than, the normal 14" twist barrels.
hope this helps.

Tom C.
01-05-2008, 06:46 AM
if this keeps up i'm going to have to go back
to college for a physics degree, ah heck i'm
just gonna go have fun and practice.

Patriot
01-05-2008, 09:49 AM
if this keeps up i'm going to have to go back
to college for a physics degree, ah heck i'm
just gonna go have fun and practice.

Yep, most college professors only inhibit true learning. I'm heading to the range for some trigger time too.

Mark

Fred K
01-05-2008, 09:59 AM
stash247
Very interesting post. How about letting us know who you are.
Fred K