Please explain how a bullet can "go to sleep" and get more accurate at longer ranges?

[steve123]

@steve123
Simple question

Were the holes perfectly round at 100 / 200 yards or where they out of round ?

Backing up a little here. When I say I didn't shoot it that much I mean I had about 1200 rounds through it over the 3-4 years I owned it. Probably 400-500 were experimenting and load work with 350 SMK's, which the gun absolutely hated and 330 lehighs, which BTW past 1 mile didn't shoot worth a darn but excellent inside of a mile, another mystery.

Near as I could tell the holes were normal. It could be that the wobble, if that is the culprit, is unmeasurably small? Who knows?

And I know what you are getting at but there must be more going on here than bullet stability alone. The way Zenbiker describes the phenomenon is the best I've seen anyone describe it. He the brainy man.

You remember Noel and the other solid bullet makers wresting with twist rates, gain twists, how many calibers in length a bullet was, shape, weight ,etc ,etc to get a solid to work correctly at distance. So apparently at the ragged edge of projectile design there is fine balance of parameters needed for a lengthy solid to work.

With standard bullets I've never noticed any problems at normal distances and out to ELR distances till I've gotten to transition distances. I have seen accuracy go down hill near or at transition to subsonic with some of them. On the other hand at a certain point past subsonic those particular bullets seem to go there way pretty good. The only way I can describe is for a hundred yards or so during the transition it's hard to hit stuff but past that it's easier even though the distance is farther.

I really don't want to argue about the subject because I'm no expert. All I can do is state what my experiences were. Word picture coming...Haha, it's kind of like I saw Bigfoot and tried to describe him but few believe me, maybe only those rare few that have had that particular experience. The description...He was about 9 foot tall, brown and harry, walked on two feet but past that I don't know what I saw, all I know is it wasn't a bear or Bobo walking around in the woods naked, LOL.

There's 5-6 guys here on the Hide that have seen how well that 375CT did at distance. Until the barrel fouled, which was about 30 rounds, it rocked.

The end, or maybe not.

 

[George63]

I will say the same as last time this came up:

If you can convince yourself that this happens, you need to go back to school - your science education is severely lacking

 

[Lowlight]

Having done the stability test, and I have more bullets from Noel on the way, I can tell you from the tests we did the lack of stability was noticeable. We saw it.

The GS Customs were a great example, the tumbled, they fell out of the sky, we could not hit at car with them at 1000 yards. We shot paper at 1500m as well as 500, and 1000. We saw bullets hit sideways. This was dramatic and not subtle. Also the guys at Gunsite with hundreds of thousands of rounds of experience did not subscribe to the sleep theory. Speaks volumes.

the twist rate required by some of these is because of the length and design, as well the driving bands. I have a gain twist in 338NM that is like 13-5.4 twist. It's because they don't want to rip the jackets or bands off more than anything else. So what you think means one thing actually is designed for something else.

Recoil matters, this is always more prevalent with magnums, because of the concussion and what you see as a result. We effect the shot far more than many want to admit. A lot of it is subconscious so you can't control it and it's not your fault, you just have to get used to it.

 

[Greg Langelius *]

I think that LL is right on the money about the human factor. After all, there's probably a good reason why rail guns have any popularity at all with the IBiNSTyF's (itty-bitty-nitpickin'-shooter-type-freakazoids).

I tend to recall hearing many times that parallax mismatch is the leading cause of 'unexplained' dispersion anomalies. I suspect that some of that hearing might have been the occasional echo.

Question: Does bearing length have any bearing (pun not intended...) on twist length, or is the overall bullet length more important? Also, what observed effect(s?) did the gain twist have on overall performance? I.e., does the gain twist alter the drive bands in and of itself? Logic suggests it might. I.e., could slugging the barrel show such alterations?

Question: Do boat tail/rebated bullets exhibit more of whatever it is we're talking about here because the muzzle blow-by has more time/opportunity to effect a tipping action on the projectile during its emergence from the muzzle?

Question: Do gyration (circular) and nutation (curlicues along the circle's path) cause bullet spin to degrade more quickly? IMHO increased yaw implies increased drag. Could this (supposed) increased drag cause the spin rate to degrade far more quickly? While we're thinking about this question, try to imagine a combination of yaw, nutation, and transonic turbulence; and how this could explain transonic departure from the established trajectory. Consider the potential for yaw-induced swerve.

Question: Does yaw accentuate drop/drift by imposing a higher drag load on the projectile?

Question: Regarding recoil, would there be any value to a bipod mount (or a front rest adapter pad) that involves a sliding shaft which slides in parallel to the bore axis? The shaft would be allowed to rotate freely as a consequence of rifling torque. It could be incorporated along with a lower buttstock (or rear bag adapter pad) which also slid and rotated along a line parallel to the bore axis and accommodated rotation due to rifling torque. This should minimize some of the rifle's sensitivity to cheek pressure while emulating some of the better features of a rail gun.

In the external ballistics context; the term "yaw" is also meant to include pitch. IMHO, yaw describes the angular deviation of the bullet's spin axis from the line of flight (trajectory). IMHO, yaw increases drag (often dramatically). IMHO, this means that when yaw occurs, effective BC is compromised.

Greg

 

[steve123]

Something else I forgot to mention is my rifle weighed 34lbs and had a solid 3" wide block of 1" thick steel solidly bolted to the aluminum chassis which was glass bedded to the action. It also had a custom aluminum bag rider fashioned to match the shape of my Edgewood rear bag filled with heavy sand.

I shot it off a Farley front joystick rest, bottomed out all the way down on it's lowest setting and shooting F-class style off the ground. Suffice it to say it was nearly impossible to pull shots with it. Well after thinking about it, no other rifle I've ever shot was as steady.

Being a 6 time AZ state FT air rifle champion as well, when "follow through on the shot" is of utmost importance in the discipline. I think I've learned a thing or two about how to shoot a friggen rifle. Good grief guys, Cmon man give me a break here!

The 350 Jamisons don't have drive bands and the 330 Lehighs are a "hybrid" bore rider, whatever that means. I will not pretend to know or give any kind of explanation regarding the physics involved with - what, where, when or why a bullet does what it does. All I care about is if I can hit stuff with it.

Another thing worth mentioning is how hard it is to spot hits on steel with the solids. Those splats are the size of a nickel. So what ends up happening is we know we've hit the steel but can't tell where on the steel the strikes are, then have to drive down to see where we've hit the steel and drive back to make a correction which is a real PITA. This was the case with the first two pics. On the first steel you can see a few high shots barely on the steel. A correction was made and as you can see the vertical is very tight, maybe 5" at 1450Y. It was windy enough that I had to aim 1 to 2 widths of that steel to even hit it with the 30 cal. With the 375 I was aiming at the edge or half a steels width off. On the middle steel on a different day you can see the same thing, a few high shot's, a correction was made and two 4 shot groups, one is 4" and the around 5.5". Greg, the parallax must of been really off to shoot those two back to back sub half moa groups at 1000Y huh? Just think if I'd dialed that parallax out they'd been 2" groups, LOL.

 

[Lowlight]

It's because they don't want to rip the jackets or bands off more than anything else.

Said, both... because it happens to both.

Again, if the holes were round... well, why bother repeating.

How does a dumb bullet that starts out "wide" at 100 yards, close up ? Who is driving it ?

Instead of explaining how awesome you know you shoot, explain to everyone how the accuracy / angular cone closes as all shooting is angular, so by your thinking the cone starts tiny at the muzzle opens up at 100 - 200 yards, then closes back down at 1000+ that is essentially what you are saying. Picture the cone, then picture the cone getting smaller at distance instead of following the angular trajectory. Pretty sure that defies logic in a lot of ways.

So it drives out of the muzzle, opens up at 100-200 then from that point either ceases to open any more, barely at all, it just goes perfect straight from then on, loses it's angular growth and just stays in line.

Now, if Jamison installed a little guy with a steering wheel, then it would make perfect sense.

 

[CoryT]

The problem is that everyone who ever describes this phenomenon is using separate groups of shots, and therefore two completely different sets of data, then trying to combine them into a single event.

Tell you what, try setting up a piece of Saran wrap at 100, right at the correct elevation to catch the trajectory of your 1000 yard shots. Now shoot your 1000 yard sub MOA group and report back with the group size on the Saran wrap. When you get a group that is larger in angular measure than the downrange group, let me know. I'm not going to live long enough for that to happen, but I'll try to give you 20-30 more years to get there.

 

[Niles Coyote]

let sleeping bullets lie...

 

[Gunfighter14e2]

The problem is that everyone who ever describes this phenomenon is using separate groups of shots, and therefore two completely different sets of data, then trying to combine them into a single event.

Tell you what, try setting up a piece of Saran wrap at 100, right at the correct elevation to catch the trajectory of your 1000 yard shots. Now shoot your 1000 yard sub MOA group and report back with the group size on the Saran wrap. When you get a group that is larger in angular measure than the downrange group, let me know. I'm not going to live long enough for that to happen, but I'll try to give you 20-30 more years to get there.

Can an has been done with lasers an video camera at trigger break, no cigar. Not a loose nut behind the bolt issue, most of the time.

 

[Lowlight]

[MENTION=15834]steve123[/MENTION]

I got Davide on here to email some groups at 100m with his 375CT

5 Shot group with this rifle... @ 100 meters

So, this must be the "exception" to the rule.

When the same load and rifle was put in the hands of a different shooter it did this:

Here is a close up of the Holes in the Paper

It's every bit as convincing against the "going to sleep" argument as anyone who say, "But Russ saw the same thing" ... well there are those who don't.

When everything else is stripped away, the Shooter Appears to be the deciding factor. Instead of understanding this, people want to view it as an "Attack" on their manhood and blame everything else.

 

[zenbiker]

"stable is stable....otherwise the bulletholes would be oblong at 100 yards (paraphrased)."

I have no intention of starting a flamefest, especially with a guy who has more experience than I'll ever have. Consider this a quest for information, and the fact that this is the internet, where intent of words are often lost due to lack of non-verbal cues.

We know that bullets, especially the long ones we love so much in ELR, have a very complex motion; they spin in excess of 30,000 rpm while yawing around their center of mass. This yawing motion literally points the bullet in a new direction of flight, but the immense gyroscope moment on the bullet forces it back toward the original line of flight. This is referred to as precession and is a well recognized factor of exterior ballistics, and why a 'good' load forms a circular/cloverleaf pattern on paper, Again, many years and many dollars have taught me that the best shaped, i.e. "roundest" group, is often the best load, not necessarily the smallest group/load at shorter distances. Did you ever wonder why bullets often 'cloverleaf'? Simple...they are very close to the distance of maximum stability and minimal precessive movment that makes the ever-sought-after "bug hole". The reason we don't see "bug holes" at LR-ELR is that other atmospheric and human factors come into play to make a "bug hole" at 600 yards a fluke of luck.

Precession is a factor of "stable" flight, but "stable flight" of a projectile lacking aerodynamic guide surfaces, i.e. wings and/or tail fins (missiles) is a very complex thing. What we percieve to the naked eye on a poor record surface (paper) as a round hole may actually oblong, but to such a minute degree that the system we use to evluate it (the human eye and possibly a slide mic) can't detect it. The truth s that it does not matter as in this 'stable' flight it is so small as to be insignificant because the precession that produces it it a stable system so the projetile is almost traveling perfectly straight downrange until transonic transition when the gyroscopic stability may be slowing enough to no longer keep the bullet on a "straight" fight path and the bullet beins to tumble, and groups open up.

This shit makes my head hurt, but it's a fact of our vocation/profession. Now that we know about it. we can return to actually pulling the trigger with a better understanding of what we see on paper.

"When everything else is stripped away, the shooter seems to be the deciding factor..."
Hallelujah and Amen, Frank, but these groups do not display the degree of difference that precession can account for at different ranges, only excellent shooting with a top-flight HIGH RECOIL ballistic system at a given range. A fool could argue that the holes in the CLOVERLEAF shaped group next to the calipers aren't perfectly round, but my momma didn't raise no fools ; )


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[one shot ST]

I've use this load only for 2 distances, 100 meters to check muzzle velocity and group, 960 m/s SD less then 1 m/s, the following step was to 1450 meters, was dead on with FFS prediction..

starting from right to left, 3 shots group, 2 shots groups and 1 shot....375 CT rock solid, the single shot target is 15 cm x 20 cm

 

[Lowlight]

The point was, Steve123 posted that the ELR Bullets, especially in his experience don't "group" well at 100 yards because of the sleep / stability factor. That both He & Russ from DTA could not get the 375 to demonstrate positive (read: small) 100 yard groups but they shot Sub MOA at distance, which in their mind demonstrated the theory that inside 200 yards the bigger 375CT was still unstable but once it got "rolling" beyond 200 yards it would group sub MOA.

Here I am presenting that a shooter can shoot Sub MOA groups at 100m with a 375CT, This load works at both 100m & 1450m. So if the bullets are unstable who did he manage sub MOA 100m groups. I Believe Steve said his best group at 100 yards was 2.5" yet it shot Sub MOA at distance. (the question would also be, did every single round fired at steel hit ? ) Did he truly group at 1000+ yards or just manage to put rounds "in a group" on steel.

The yaw, roll, spin, (which all bullets spin fast) is microscopic and cannot be seen. however if they not working at 100 they will not work at 1000. There is nothing to straighten them out like that, especially that far.

This argument has been used for all bullets, not just ELR Bullets. As I noted much earlier, find a guy who says, "X Bullet at 100 yards doesn't work" I will show you a guy hammering them into one hole. By this thinking, we could not put these same bullets into a single hole at 25 or 50 yards, which the last time I shot at 25 yards for score, I put 10 round (off a bipod) into one single hole... literally 1 single hole. These were boat tails which according to Sleep Theorist don't work at close range.

Read what CoryT wrote... The challenge is open to anyone...

Put Rice Paper in the path of the bullet at 100 yards, and aim in on your steel at 1000 yards and if the group at 100 is bigger, you busted the idea on how angles work. (Now the only way this really works, is, if you are adjusting for windage on each round, and the wind is assisting you on steel. If you read the wind for SHOT 1, and hold that, then read the wind for SHOT 2 and hold that, you would have a different look at 100 yards, because the shots are different. (which he also noted that people analyze two different sittings as the same thing)

If you want to take individual posts out of context, you are more than welcome to do so, but you loose comprehension of the overall debate.

 

[zenbiker]

Frank. you're the man, but I don't see where I have misinterpreted any posts, respectfully. To be blunt, I have seen rifles of less precision shoot groups of 2=3 MOA at 100 meters, only to print sub MOA groups at 400 yards or beyond. The excellent groups you bring to the table neither prove nor disprove the precession theory; in fact the shape of the triangular groups only seem to reinforce the theory.

I'm curious as to how you know that precession is 'too small to see'; to me,the biggest problem in proving or disproving prescession is the shooter himself Only very experienced shooters who put rounds downrange daily are familiar enough with their systems to know if during the last shot fired was different from the previous shot in terms of whether or not they drove the rifle the EXACT same way or not. In fact, the rice paper test is flawed from the start unless the human component is removed from it and a form of precision return-to-battry rail gun is used, but even then, as I stated before, so many things happen between the time of flight between 100 and 1000 yards in terms of atmospheric variables that unless atmospheric conditions are within the accuracy potetial of the weapon and load used, little can be concluded other than groups at 1000 yards are different than groups at 100 yards. Thermoclines bounce bullets off layers of air at different temperatures; generally a 1mph full value wind is worth 4 to10 inches at 1000 yards; spin drift, Coriolis, jacket uniformity, lead core physical state, and a myriad of other things will affect each successive shot. The 1000 yard IBS 5 shot group is around 1.5"; wouldn't you like to know the group thos five shots formed at successive distances on the way to a group many shooters struggle to achieve at 100 yards. Or, as Pennsylvania gunsmith Bruce Baer opined, "the wind can blow a bullet out of a group or it can blow it into a group." I agree with your statement that for every (bad) shooter blaming prescession for large 100 yare groups, there are those who are shooting good 100 yard groups, because whethe they realize it or not, those excellent shooters are engaging in practices to have a bullet in a stable flight pattern right from the muzzle.

Don't just take my word for it. Do a Bing Search using the term "precession of a projectle", take a cold six pack, and start slogging through the results. Precession does exist; it can be subtle or it can be jaw dropping in it's magnitude. BUT: in the end, you and I do agree on this: The shooter is the final determinant in group size, affecting the final outcome by choice of projectile, charge of powder, quality of brass and projectile and their uniformity round to round, neck tension, whether the loaded rounds are surgically clean of lube or not, type of rest used, degree of grip on the gun quality of the optic employed, and dozens of other factors that we as shooters strieve to eliminate or make uniform from shot to shot. Driving the rifle is only one varable in ELR accuracy.

I will be the first to admit that i can misinterpret a post, but the fact of the matter is bullets go through varying stages of gyroscopic stability during flight, and this varying stability can affect the bulle flight path. I do agree with Bill Shehane, who holds that 'if a bullet don't shoot well at 100 yards, It prbably ain't gonna shoot well at 1000"; the trick, however, is recognizing what a good group at 100 yards looks like for an ELR load. F class shooters are known to have pet loads for each firing line - I wonder why? We agree on much more than we disagree on, including that any shooter using precession to bemoan 'large' groups and prove 'this gun don't shoot' need to go back to the books and realize that precision shooting is much much more than just stuffing a round of ammunition in a rifle, be it an $1000 rig or a $10,000 rig and pulling the trigger. As further example, I pulled this quote from another thread on this forum:

Very true that everyone has a different method for load development. A local BR Shooter who recently posted a 400-17X at 300 yards uses the following method.

If he's getting "Vertical" he merely increases the powder charge. Keeps increasing until the vertical turns to a "triangle" (he uses 3-shot groups for workup) and then reduces the increments of added powder. For .308 he increases charges by .4-.5 gr at first and then goes down to .2gr increases until he gets "Single hole". When the next .2 gr increase goes back to the "triangle" he backs down to the middle of he best loads. Last adjustment is OAL for the fine tune.

The rest is all consistency in the shooter's actions.

All the best,

Wes





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[Lowlight]

I have already stated over and over to the point I am bored with it, go back and read.

a SHOOTER can make the group bigger or smaller. a SHOOTER because they can't see the group can shoot better at distance, that does not mean the bullet is doing it. Nor does it mean a group that is sub MOA at 1000 yards started off bigger at 100 yards. I don't care how you spin it, you can't shoot a sub MOA 1000 yard group that started out as bigger than 1 MOA at the same time. Can you shoot poorly at 100 and shoot better at 500, sure, but there is an external factor that is not because the bullet is unstable at the shorter range.

Confusing bad results at short distance and good results at long is not the same thing. Shooting a small group with help from the wind is not the same thing as saying the bullet is inherently flawed in its flight path then it corrects itself.

I shoot weekly, CoryT daily, so please, try googling angles and then come back and explain how in the same shot, the same ballet closes the angle on its own.

the bullet is either stable just past the muzzle or it's not, it will not stabilize itself past 100 yards if it's unstable to begin with. There is no pilot to correct the flight.

Give me the load, tell me the one you think it is and I promise, I bet, I put them in 1 hole at 50 yards. Show me the load you are describing and I will shoot it on camera. What is the bench rest / F Class load ? Tell us all the bullet. Please.

 

[Lowlight]

We are not talking about load development.

We are talking about that is unstable at 100 yards that closes the group on its own.

If you have a gun that shoots 3 MOA @ 100 yards and sub MOA at 400 yards I want to see it. Give me the specs. If it's there tell me I will fly out to witness it. But tell me the load you think is unstable at 100 yards that then rights itself at 400 yards and beyond. I will replicate it as I want to see it for myself.
this is not about someone's pet load, it's about an unstable bullet at 100 yards that not only stabilizes itself after, but then closes the angle to reduce the group. I want the specs...

This is not about some guys idea that his winning 300 yard group is "X" and his winning 600 yard group is "Y" it's about one shot that starts big and ends small because it spinning itself into a smaller angle than it started with. That one bullet that doesn't work at close range but works great at 1000 yards.

Can a person load poorly or see something in development, maybe. But I am not talking about load development I am talking about the bullet design that doesn't stabilize at 100 yards but works at 1000. We aren't talking about fine tuning an already good load into a better load for a specific distance. Read your own quote he removes the vertical and fine tunes it. Not the same.

I want the bullet that "sleeps" after 100 yards. Give me the 3MOA load at 100 that hits sub MOA at 400?

 

[George63]

I say have a rule that anyone who believes this shit is banished to Arfcom - there they will find plenty of dingbats to buy into voodoo physics

and this will not have to be hashed out 3 times a year

 

[steve123]

All,

For clarification here is what I wrote in my original post....

"""Years ago, when I first got my Lawton 375CT, I tried doing load work at 100Y and 200Y with the best being 2.5" five shot groups at 200Y. I was totally frustrated to the point of sending the rifle back. Here I had fired hundreds of rounds already doing the load work and not even tried the rifle past 200Y because I thought I wasn't done yet. I mean why bother trying right?- Well I had 10 rounds left and gave 400Y a try and got two back to back 2.5" groups and freaked out a little, LOL, wondering how on earth that happened."""

I stated that my rifle shot 2.5" at 200Y and then 2.5" at 400Y. This was with the same load and on the same morning. """"""NOT 2.5" AT 100Y""""" The rifle averaged 1.25" at 100Y so some groups were smaller and some bigger. I shot a few small groups with the rifle at 100Y, which was a glitter of false hope for me at the time, but only because I had shot so many groups during load development there were bound to be some smaller ones.

My 375CT had the original "11.5 twist lost river bore" in it. Perhaps this has something to do with the oddity???

Here on the Hide I've seen posted some very good groups shot at 100Y/M with different 375CT's with different twist barrels and using other brands of Solid projectiles. I am not saying every different type of solid projectile shot from various rifles/barrel configurations exhibit this phenomenon.

To all again, I apologize if I came off in a haughty manner concerning my few accomplishments as a rifleman. The crux of my motive was trying to establish some credibility in the context of skill set level.

 

[Greg Langelius *]

IMHO, when performance/MOA at different distances varies in a contra-intuitive manner, I really do believe we are dealing with an operator-induce anomaly. I include parallax compensation error as an operator-induced anomaly.

IMHO, groups that can be counted on the fingers of a single (or even both) hand(s) do not constitute a sampling of sufficient magnitude to be indicative of very much, and certainly not one of absolute performance. I would not be wanting to accept and mass produce a developed load based on one or just a few 5rd groups.

Where dispersion is concerned, it could theoretically be considered as a cone of divergence, but my experience suggests it takes the shape of a flaring trumpet, increasing rather than decreasing as distances get incremented. Single instances to the contrary would be statistical anomalies, IMHO.

Finally, no human performs in a perfectly consistent manner. If I could, I'd be a champion, and that is most definitely not the case in my regard. If I could and was a champion, I'd still be relatively certain I always left something on the table, no matter how well I performed.

IMHO, there is always some small bit of operator error in all groups.

Greg

 

[zenbiker]

Look, guys, this is not worth getting jacked at each other over. There are three kinds of people; those who believe unquestioningly, those who reject unquestioningly, and those who consider in fact, that there might be something out there new to learn. Frank, with respect, the quote from the shooter outlining his method of developing loads proves the point of STABLE precessive flight; the larger round groups are those where the STABLE precession is larger than in the small groups. As I said, many factors affect bullet flight is affected by many factors...like powder load. This shooter proves my original STATEMENT about the Theory of Precession and Nutation. But believe me, it is NOT my theory. Just ask any ballistician in the Army, Navy, Marines, or any other professional who sends 2000 lb projectiles over the horizon to hit a target area the size of a tennis court.

Like I said, do an internet search, and this time use the search term "magnitude of precession and nutation of a rifle bullet". Here's and example of the thousands of hits you'll get:

http://www.nennstiel-ruprecht.de/bullfly/index.htm#Figures

We've all made our points and had our say; personally, I'm gonna let it drop. This is still the best shooting website on the net.

Wes

PS: If anyone doesn''t know the story of the Zen Master and the empty cup, PM me.


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[Lowlight]

@zenbiker

Your "magnitude of precession and nutation of a rifle bullet" is an incorrect understanding of the theory. You need to go back and read it.

There is nothing in their theory that says the bullet corrects itself, except in the cases were patents are trying to add fins and air brakes to the bullet. Look at physics, they talk about a bike wheel spinning on a string. They clearly state that if you have an unstable wheel spinning you cannot correct the spin or better, the wheel does not correct itself as it slows down. This does not happen.

You are misunderstanding what you are linking. Here is a shortcut for everyone:

On a physics Forum this was asked, and here is one of the answers:

Also, I still don't understand the precession of a projectile, as in my post in the mechanical/aerospace forum that nobody seems to know the answer to.

Read more: Physics Help and Math Help - Physics Forums

You're link also says nothing about correcting stability, it just that the spin controls the yaw (paraphrase) so please stop repeating the words because you misunderstand the meaning. It also says, in "absence of spin" you have more yaw, at which point it tumbles, we don't have any absence of spin, at all.
It's a theory, and not a very good one.

 

[Lowlight]

Here in the same link...

It can be shown by a mathematical treatment that this condition is fulfilled, if the gyroscopic stability factor s[SUB]g[/SUB] exceeds unity. This demand is called the gyroscopic stability condition. A bullet can be made gyroscopically stable by sufficiently spinning it (by increasing w!).As the spin rate w decreases more slowly than the velocity v[SUB]w[/SUB], the gyroscopic stability factor s[SUB]g[/SUB], at least close to the muzzle, continuously increases. An practical example is shown in a figure .

Thus, if a bullet is gyroscopically stable at the muzzle, it will be gyroscopically stable for the rest of its flight.

You have increase the number, not decrease it to fix an unstable bullet... so how does a slowing bullet correct stability when clearly he is saying you must increase the spin.

However, the gyroscopic stability condition only is a necessary condition to guarantee a stable flight, but is by no means sufficient. Two other conditions - the conditions of dynamic stability and the tractability condition must be fulfilled.

And read his caveat...

as the bullet in the drawing is assumed to be dynamically stable

 

[Lowlight]

Bingo !

in the fine print from the page

If, on the contrary, a bullet is dynamically unstable, the angle of yaw increases.
The occurrence of an initial yaw close to the muzzle is by no means an indicator of bullet instability. In some recent publications, the statements "bullet is unstable" and "bullet shows a (big) yaw angle" are used synonymously which is incorrect. On the contrary, an initial yaw angle at the muzzle is inevitable and results from various perturbations.

 

[zenbiker]

OK, Frank, I concede this discussion - but not my personal beliefs or shooting practices- based on it. Just as long as those beliefs and the practice they have led me to gets my bullets to go where I want them to go. FWIW, I wouldn't shoot a load that didn't shoot 'well' at 100 yards, counting on it to go to sleep downrange to hit a target. I have witnessed the phenomenon we have been discussing and learned to us it as a sign in load development - chiefly, that I'm on the right track, and a tweak of seating depth or bullet pull is usually all that's necessary to pull it all together. I remember that distinctly some 15 or so years ago when I started trying 240SMKs in a standard SAAMI spec 300 WinMag Match chamber (see Precision Shooting magazine, article "The 30 WinMag-An Old Dog Still Hunts" written by yours truly)- something that highly experienced experts denounced, decried, and dissuaded me from doing...."You need a long throat"....You'll blow the bolt back in your face"...and other perjoratives of fervor equal to the denial that gyroscopic precession and nutation are 'myths' in this discussion. Ironically, this quest was where I found that uniform group shape usually was superior to smaller, irregular groups, and finally found two loads that shot 1/2 inch at 100 yards and depending on my ability to handle the conditions, sub-moa 5 round groups at 1000 yards and proof that the 240SMK is a viable, safe, and accurate projectile in the 300 WINMAG where "conventional wisdom" held that a 30/375 derivative was or a special long throated chamber was the only safe cartridge that could shoot the 20 safely. Ironicallly it was during that endeavor that I had MY realization of gyroscopic stabilization, and it has served me well since. While I acknowledge Precision Shooting is not nearly the bible to the long range shooter that Long Range is, but it still had a lot of good information if you knew where to look for it. Looking forward, BTW, to the next issue and the new sighting system that almost guarantees a hit out to 1200 yards if you have $30K to drop on it.

I don't have your experience Frank - to busy at another vocation. I also acknowledge and respect your depth of experience and learn something from it almost every day. But I know what see with my own two eyes. I'll stand up and take a beating for it because in the end, you don't have any more evidence against gyroscopic or precessive stabilization that I have for it. Let's lock this thing up and get on to other topics, like the application of 3D CAD/CAM to bullet design - design in the morning and shoot it in the afternoon. That's something I think you can get behind.

Wes





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[Gunfighter14e2]

Ever seen trace wobble close in?

 

[hlee]

OK, rank, I concede this discussion - but not my personal beliefs or shooting practices- based on it.


Wes

Beliefs retained in direct contradiction to empirical evidence. Why religion will triumph over reason.

One point I need some clarification on. Gyroscopic stability is affected by the rate of rotation and the velocity of the bullet. Higher velocities require faster spin rates (all else being equal) to be "stable." If the bullet velocity slows faster than the rate of rotation (this is generally assumed, does anyone have evidence) then a bullet will gain gyroscopic stability as it travels down range, correct? Of course, this would not correct course deviations that have already occurred, but could help to minimize further decay. For example, Greg L envisions a "flaring trumpet bell" as the bullet deviation from poa. Could some bullets exhibit less flaring than others?

 

[Greg Langelius *]

Re; the flared bell; I'm talking about dispersion, not stability. The increased dispersion is, IMHO, due to the compounding of environmental condition variances over the entire string of fire. Baseline dispersion should follow the course of a straight sided cone. It's when we add the environmental variances between shots that the bell flares. I will concede that the odds allow for the flare to be negative (narrows), but that has not been happening with any consistency in my own personal experience.

Gyroscopic stability is affected only by that drag component which resists rotation; it always slows at a predictable rate. The emphasis between gyroscopic (aka static) stability and aerodynamic (aka dynamic) stability always transitions away from dynamic and toward static stability, since MV degrades at a far quicker rate than RPM. This is not a good thing, because just when the trajectory curve becomes more pronounced, the dynamic stability is at its least, making it less effective at realigning the bullet's long axis with the (curved) line of flight.

The net effect is an effective upward pitch (which is included in the term 'yaw'), increasing drag dramatically, and that increased drag accentuates the effect of whatever gyroscopic instabilities are present. Drag and aerodynamic deflection (and/or lift) are but different manifestations of the same force. There is no drag without deflection (even if it is directly along the line of flight), and there is no lift without drag.

Can some bullets shoot a smaller flare? I think so. A higher BC and velocity can combine to reduce time of flight, which should therefore reduce the magnitude of the flare, as well as drop and drift..

Is this an effective, efficient approach? I don't think so, because any gains will be achieved at the cost of deceased bore life.

The best barrel is the one that shoots to its native degree of accuracy the longest. I am not out to excel, I am out to achieve my own limited goals, and bore life probably assumes a higher priority for me than for some others.

As long as performance is consistent, drop and drift are (or should be) known values. Better to know your rifle and its performance over a wide range of conditions than to firewall the throttle and count on luck to get one through the windy sections (aka point, pull, and pray...) Even if it works, you're burning barrels at an unnecessary rate.

Greg

 

[Fred_C_Dobbs]

secondofangle, the shooting community doesn't do itself any favors by habitually failing to distinguish "accuracy" from "precision." Then we wonder why we can't make sense of issues like this. Group size is a measure of precision, not accuracy. If group size increase slows at greater ranges, then statistically, precision is increasing. But accuracy isn't. If dispersion increases by 1" before the bullets go to sleep, that's 1" of accuracy that ain't never coming back.

I have never witnessed this first-hand but logic dictates this only should happen when shooters are pushing the limits of stability with their bullet/twist combination. Which is why the DoD standard is a stability number (Sg) of 1.5-2.0, while civilian sources suggest a minimum Sg of 1.4. By definition, a bullet/twist combination with an Sg of 1.0 should be "stable," but undoubtedly would take longer to go to sleep, and would have no margin for error.

Bob McCoy, a highly-regarded ballistician, wrote in his 1999 book, "Modern Exterior Ballistics" that epicyclic swerve was the cause of the phenomenon. The late Gale McMillan (founder of McMillan Rifles) echoed that sentiment, further explaining that minor variations in muzzle velocity caused the bullets to strike the target at different points around what he termed "the spiral" before they go to sleep.

I've seen the term "helical" used in relation to the epicyclic path, but McMillan is the only one I've come across who called it "spiral," but I suspect he was toning down on the 50¢ words in deference to his audience.

However, Bryan Litz considers this exact point (even referencing McCoy's book) in an article on epicyclic swerve on his Applied Ballistics web site:

The theory goes:

“The bullet leaves the barrel with some degree of pitching and yawing motion. At short ranges, before the pitching and yawing damp out (i.e., before the bullet ‘goes to sleep’) epicyclic swerve is responsible for larger groups because the bullet is flying on a ‘corkscrew’ trajectory. After the bullet ‘goes to sleep’, the bullet flies straighter, allowing smaller groups at longer range”.

His simulation (using a custom 6DoF simulation software) indicated that dispersion owing to epicyclic swerving should be on the order of hundredths of an inch. Video of the simulation is on that same web page, definitely worth a minute and a half of your life to help you get your mind around the concept.

Litz concludes,

The phenomenon of smaller angular groups at longer ranges was not disproven. The only thing I've shown is that if the phenomenon actually happens, epicyclic swerve is not the cause of it.

Note his word choice: "smaller angular groups at longer ranges". Not smaller groups, smaller angular groups. He effectively is dismissing the matter of smaller groups out of hand, but is unconvinced on the subject of smaller angular groups.

Judging from his conclusions, Litz has never witnessed this phenomenon either (or at least hadn't at the time of this writing). But Gale McMillan did. He once wrote,

We shot 18000 rounds of 50 cal ammo during a contract. The guns were sighted in and function tested at 100 yards and averaged 1.5 moa groups. When these same guns were tested at 600 yards you would expect the groups to run 1.5 moa or 9 inches. The 600 yard targets ran as small as 3 inches and never any larger than 6 inches as an average. Any that shot larger than 9 inches were inspected and retested.

So McMillan seemed pretty convinced this "smaller angular groups" phenomenon does in fact occur (as are more than a few other shooters). If this had happened to Litz, I'd bet he'd devise a way to get to the bottom of the topic.


As an aside, while I was researching this topic, I came across a report from the Army Research Laboratory indicating that the penetrator (the 'dart') from a fin stabilized "sabot" round also experiences yaw and pitch excursions immediately after exiting the muzzle, and for the exact same reasons spin-stabilized bullets do. At that moment, I had an epiphany.

I was trained in tank gunnery back when the main guns still were rifled. When we were briefed on the construction of the (APFSDS) sabot rounds then in use, the instructor made note of the fact that the driving bands on the sabot doubled as a bearing. The driving bands were what engaged the rifling, so they couldn't help but spin, but they were designed to pass as little as possible of the spinning along to the sabot.

At the time, I puzzled over why you would even want to isolate the sabot from the spin of the rifling. When I read the ARL report, it hit me. Pitching and yawing is just pitching and yawing, until you add rotation. Rotation brings with it gyroscopic precession, which couples with yawing and pitching to produce epicyclic swerving. Which adds another (unnecessary) variable to the sabot round's external ballistics, so they use slippery driving bands to prevent it.


The white ring girdling the sabot is the 'slippery' driving band.

Inquiring minds want to know (even if it takes 100 years to figure it out).

 

[Aeon1]

Another excellent reference to read on this subject is Harold Vaughn's book Rifle Accuracy Facts. I understand it is out of print and used copies are priced fairly high but it has some great info on this very subject. Vaughn did a lot of actual scientific testing on his own after retiring from the Sandia Nationa Labs, Aeroballistics Division.

 

[Lowlight]

The only problem with the epicycle swerve or the helical swerve is the center of the bullet remains fixed as noted here:

Imagine that the CG of the bullet is fixed at the centre of a co-ordinate system and that the bullet approaches an observer´s eye. Then its tip moves on a helical path (as indicated by the curved line) into the direction of the arrows. At muzzle exit (t=0) the yaw angle can be small, but increases to a maximum of approximately 1°, then decreases again to almost zero.

So you have the middle secure in it's path and the tip moving, that still puts the mass in the center. Which is why it is not noted.

McMillans observations do not take into account the "Human Factor" he does not mention that the recoil on a .50 as viewed through a scope is big. We are effected by recoil and how our brain perceives this as we have built in defensive mechanisms to protect us. (READ: FLINCH) When we move out from 100 yards, we open up the FOV, the distance, etc, and the body is now more comfortable with the idea of a controlled explosive in front of our face. So we tend to settle in and relax. This is why some people tend to shoot better at distance when they can't see the actual group, but instead focus on the reticle.

The best example of our mind acting subconsciously is what Jacob @ RO called the Refrigerator Hypothesis

Consider your average shooter and his best 100 yard group attempt. He puts it in his mind he gonna shoot a 5 shot group so perfect that when he is done, he will cut it out and put it on the Refrigerator for all to see. He begins by shooting a perfect 3 shot group, and see this one hole masterpiece, he now proceeds to Shot #4 and blows the group opening it up. Deflated he fires Shot #5 and it goes right back into the middle of original 3 Shot group, making a perfect 4 shot group of .25" with that one flier out 1/2" away. Neither the gun or the bullet suddenly decided to fuck the shooter out of his perfect 5 shot group, it was his own mind. We have seen this over and over... we allow our mind to control the situation. Now understanding this control the subconscious has on us, image that in a defensive position. If you notice all most all of these "going to sleep" stories involve Magnum or larger guns, very rarely do you hear about it with small bullets except from new shooters. That is clue.

The tip of the bullet maybe moving, but it moves in the wind too. The core of the bullet follows a direct path. As noted above, and referenced from the link, yaw exiting the muzzle is not bad, it just is... these movements are on the microscopic level. The designers of the bullets are not pushing out marginally stable products, they know it is stable from the moment it leaves the muzzle otherwise they would go back to the design lab and fix it.

 

[Greg Langelius *]

To my mind, each shot is an independent match, unrelated to any other match. A bad shot doesn't affect any other shot. If I miss, I move on to the next match, which is logically unencumbered by anything previous.

What's past is past, unalterable. What's future is fantasy, yet to find fruition. The only shot I can have any influence on is the present one; any thoughts to the contrary are invalid. Only I can make myself fail, and I don't do that until I quit. So I don't quit.

Groups can be interesting, but what I do is to defeat targets. That which defeats more of the available targets is preferable.

Greg

 

[zenbiker]

[MENTION=15834]steve123[/MENTION]

I got Davide on here to email some groups at 100m with his 375CT

5 Shot group with this rifle... @ 100 meters

So, this must be the "exception" to the rule.

When the same load and rifle was put in the hands of a different shooter it did this:

Here is a close up of the Holes in the Paper

It's every bit as convincing against the "going to sleep" argument as anyone who say, "But Russ saw the same thing" ... well there are those who don't.

When everything else is stripped away, the Shooter Appears to be the deciding factor. Instead of understanding this, people want to view it as an "Attack" on their manhood and blame everything else.

Frank, explain something to me. There are three groups here; are they all at the same distance?

I notice something here that bothers me in the first two groups, and that is vertical stringing. . Worse in the second group than the first, possibly due to barrel fouling or different shooting technique. The third group is a triangle/round shape, but the bulletholes are arguably not round. Was this third group the same load as the first two, and fired at the same distance? Why was it so different in shape than the first two?


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[zenbiker]

I have already stated over and over to the point I am bored with it, go back and read.

Bored with it? Or no more able to prove your point of view so you refuse to consider it any longer? You know what you know, is other words, so there can be no more.

a SHOOTER can make the group bigger or smaller. a SHOOTER because they can't see the group can shoot better at distance, that does not mean the bullet is doing it. Nor does it mean a group that is sub MOA at 1000 yards started off bigger at 100 yards. I don't care how you spin it, you can't shoot a sub MOA 1000 yard group that started out as bigger than 1 MOA at the same time. Can you shoot poorly at 100 and shoot better at 500, sure, but there is an external factor that is not because the bullet is unstable at the shorter range.

Are you saying that because the SHOOTER (your caps, not mine) can't see a group at 1000 yards, they shoot better than they do at 100 yards where they can see the group forming? That it's not possible that the complex interplay of internal and external ballistics could not be responsible for the very phenomenon we are discussing? C'mon, that's as much as stretch as anything else brought forward in this discussion, which is I believe showing results as to what is really going on. By the way, I do agree with your statement that movements such as precession and nutation are possibly too small to be seen; however, there is no doubt that they do exist, and if they do, they will have and effect on bullet flight. I'll even go so far as to say that considering the angular forces they generate on a bullet, its a good thing they are so minuscule, otherwise our bullets would never hit anything. What we see in our groups is not the magnitude of precession and nutation, but rather the magnitude of their effects on a projectile in flight.

Confusing bad results at short distance and good results at long is not the same thing. Shooting a small group with help from the wind is not the same thing as saying the bullet is inherently flawed in its flight path then it corrects itself.

I agree; but I don't see where this statement proves or disproves anything. To me, these are apples and oranges. In fact, I mentioned Bruce Baer's words essentially to the same effect. However, I will go out on a limb and say that a stable bullet is marginally less susceptible to wind effects than an unstable bullet, and further play out enough rope to hang myself by saying that an bullet in unstable flight will not yield the ballistic coefficient that equations would otherwise call for.

I shoot weekly, CoryT daily, so please, try googling angles and then come back and explain how in the same shot, the same ballet closes the angle on its own.

I believe that is what this discussion has been about...

the bullet is either stable just past the muzzle or it's not, it will not stabilize itself past 100 yards if it's unstable to begin with. There is no pilot to correct the flight.

...and not to be Clintonesque, but this question hinges on what your definition of "stable flight" is. Physics is the 'pilot' that governs the flight of the bullet; again, back to the oft- used child's top analogy, show me the pilot that makes the wobbling top begin to spin smoothly for a period before it's rotation begins to deteriorate into a 'death wobble'; your hands do not touch it, yet it happens nonetheless. Where is that pilot? Could the pilot that can stabilize a top also have the potential to stabilize a bullet? Why do we have different twist rate barrels; one not just have one twist? If we add or subtract powder from a load, what changes besides muzzle velocity? Among other things, could it be rotational velocity?

Give me the load, tell me the one you think it is and I promise, I bet, I put them in 1 hole at 50 yards. Show me the load you are describing and I will shoot it on camera. What is the bench rest / F Class load ? Tell us all the bullet. Please.

Sorry, I don't understand this question or what it has to do with the original poster's question. There several loads for given cartridges that tend to shoot better than others; plus many shooters have a load that works for them in their rifle but nobody else's. I've wasted a lot of powder on other people's load's until I learned what to look for and adjust them to shoot well in a particular rifle.I'd ask you to tell me for what reasons. I have two rifles chambered for 300 Win, but one will not shoot the loads that I have always used in my other 300WMs. Why? Don't bother answering, because again, the question on the table is "What is the meaning of a bullet 'going' to sleep'?"
My answer is the progressive stabilization in flight of a load meets certain internal and external ballistic criteria as that bullet becomes rotationally/gyroscopically more stable in flight. This stabilization does not apply to all loads and all bullets in flight; some loads so violate the rules required for an accurate load that the stabilization hypothesized here does not occur. Best answer I can give based on my experience.


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[0311 Hesco]

Straight off of the Applied Ballistic Site:
" I learned a lot about epicyclic swerve from this project. The bottom line is that epicyclic swerve cannot cause smaller angular groups at longer ranges. The reason is because it’s so small. The main reason it’s small is because the bullet is precessing (coneing) too fast for the nose to steer the bullet very far off course. The nose of the bullet will usually trace out a complete circle in less than 10 yards for a dynamically stable bullet (one that will settle to zero coning motion after a disturbance, or ‘go to sleep’). Even dynamically unstable bullets like the Sierra 30 cal 168 gr MK complete cycles in less than 50 yards."

That being said, I believe LL is correct saying it's the SHOOTER, not the gun/bullet/voodoo/phenomenon that you all are thinking. Just like I put waaaay earlier, and many others, it's the nut behind the bolt, the evidence from a kids top is a stupid argument here, and there is no pilot in the bullet, are all sound points. May we drop this now? This is getting worn out.

LL, get the Red Bullet out, time to WAKE THESE BULLETS UP!

 

[Lowlight]

The answer to all that devil advocate playing bullshit is really, really, simple.

Have you ever seen a top spin straighter the slower it spins or does it wobble more the slower it goes. There is the real answer.

As far as the shooter crap, I already answered that with an example of group shooting.

and Zenbiker, you own link disputes your understanding, go back and read ALL of it not just parts.

 

[Lowlight]

And ps, this discussion is absolutely, positively, NOT about a pet load, it is about a bullet type, or style that doesn't stabilize until beyond a 100 yards.

It it is not about load development, it is not about what you use at 300 yard vs 600. It's about a person saying the bullet is not stabilized beyond 100 which points to designs and not a shooter' crappy load.
Personal loads are not the question.

Its about a person blaming the bullet at close distance for a poor performance.

the boredom comes from constantly having to repeat myself over, over,

 

[Lowlight]

I know how to settle this for now.. very simple,

Bryan Litz writes this and I have never once suggested anything close to it:

" I learned a lot about epicyclic swerve from this project. The bottom line is that epicyclic swerve cannot cause smaller angular groups at longer ranges. The reason is because it’s so small.

The complete quote from Bryan Litz of Applied Ballistics is:

" I learned a lot about epicyclic swerve from this project. The bottom line is that epicyclic swerve cannot cause smaller angular groups at longer ranges. The reason is because it’s so small. The main reason it’s small is because the bullet is precessing (coneing) too fast for the nose to steer the bullet very far off course. The nose of the bullet will usually trace out a complete circle in less than 10 yards for a dynamically stable bullet (one that will settle to zero coning motion after a disturbance, or ‘go to sleep’). Even dynamically unstable bullets like the Sierra 30 cal 168 gr MK complete cycles in less than 50 yards."

Me on the other hand have not thought of saying anything close, so if you disagree contact the Team @ Applied Ballistic the rest of us will wait to hear what they have to say.

 

[Greg Langelius *]

Yaw (for whatever the reason) increases TOF, and subsequently, drop and drift. Logically, the better the conformance of the rotational axis and the trajectory curve; the higher and tighter the impacts should be. The worse, the more the projectile 'falls out' of the predictable impact zone.

If you ever end up scratching your head why impacts occur lower and looser than what the calc decrees, here's your answer. My solution would be less twist, or (maybe '/and' as well) a longer bullet.

Somewhere back in the dim history of this site, there was a posting of a high speed cinematography sequence demonstrating the extreme cyclic wobble of an artillery round just out of the muzzle.

The projectile's behavior clearly demonstrated the projectile's nose gyration about the line of flight, with the Center of Mass remaining true to the trajectory, demonstrating no visible swerve, pretty much confirming LL's and Bryan's comments posted/quoted here.

Greg

 

[CoryT]

, the question on the table is "What is the meaning of a bullet 'going' to sleep'?"
My answer is the progressive stabilization in flight of a load meets certain internal and external ballistic criteria as that bullet becomes rotationally/gyroscopically more stable in flight. This stabilization does not apply to all loads and all bullets in flight; some loads so violate the rules required for an accurate load that the stabilization hypothesized here does not occur. Best answer I can give based on my experience.

That sir, is rubbish. While the coning motions dampen out as the bullet moves downrange, that is NOT the same thing as becoming more stable. If the bullet leaves the barrel and it's not stable, it WILL tumble and you'll get keyholes or oblong holes, it WILL NOT get better, and in fact at some range you will simply have no idea where a particular shot will actually land. If the bullet exit is gyroscopically stable, the typical coning motion is about .003 to .006 inches at 200 yards, which is simply immeasurable in group size. From exit, the bullet ONLY becomes less GS, because it is losing both velocity and rotational speed. As the bullet loses velocity, it may reach a point where the rotational speed is no longer enough to maintain gyroscopic stability. The 168gr MK for example, from a 1 in 12 twist becomes only marginally stable at ranges of 800 to 1000 yards, and it's this transonic instability that leads to poor results at these ranges.

Absent happenstance, where wind drift corrects an aiming error and puts a bad shot INTO a group rather than out, you are simply never getting a smaller angular group at a longer range than the same shots plotted at a closer range. Lock the gun in a rest, measure vertical dispersion only, which then mostly eliminates that issue. There is simply no physics which describes a decrease in angular grouping, excepting wind drift. Without wind drift "correcting" the flight path, a 1 MOA group at a given range can ONLY get larger as the range increases, as the bullet stability decreases and any errors in the bullet construction and initial launch angle increase it's dispersion from centerline.

This happenstance is of course, why this is so infrequently observed, and not replicated in any real testing, only passed on as 'personal observations', with no actual scientific explanation or repeatable test results.

Seeing the Loch Ness monster and believing it exists does not prove it's there.

 

[Aeon1]

I am not disputing anything in Lowlight's statement above but to add some clarification. Litz states "The nose of the bullet will usually trace out a complete circle in less than 10 yards for a dynamically stable bullet", this is true (as I understand it) but I can see how someone might interpret this to mean the coning motion is finished within one cycle. Most 6DOF data I have seen shows the coning motion is still going on out to 200yds+. How quickly it damps or doesn't damp is up to how stable the bullet was at exit from the muzzle, this stability is usually stated as GS (gyroscopic stability). A high GS and the coning motion damps quicker than a low GS. If the GS is too low (not stabilized) it never damps and can lead to high dispersion (large groups).

 

[Aeon1]

"What is the meaning of a bullet 'going' to sleep'?"
My answer is the progressive stabilization in flight of a load meets certain internal and external ballistic criteria as that bullet becomes rotationally/gyroscopically more stable in flight. This stabilization does not apply to all loads and all bullets in flight; some loads so violate the rules required for an accurate load that the stabilization hypothesized here does not occur. Best answer I can give based on my experience.

Are you saying some loads violate all the work Mann, McCoy, Vaughn and many others have done to show what happens when a bullet is launched from a rifled barrel? I'll bet your loads don't violate the rules you just got more things right with your particular combination that it just seems to defy the norm.

 

[0311 Hesco]

Wow.
This thread has surely shown me at least one thing. The First Church of The Epicycles has some very smart people as they use big words and quote their bible verses, albeit wrong. No matter what you show/tell them, they are going to stick with what they believe regardless of how many people re-explain their own literature. Let them charm their snakes and blame it on something that might happen but can't be measured by the average dummy on the range. Definitely unsubscribing to this, it makes my head hurt.

 

[LastShot300]

In terms of dynamic stabilty (Sg), the analysis is very simple.

A bullet looses stability (Sg) as it flies down range since it's loosing speed (along all angles used in 6DOF analysis) making it impossible to recover it unless an external force acts on it, which is a physics law.

Since other than wind (the only external factor that can apply "force") there is no other option to impart any change, then there is no way in pure ballistics terms, that a bullet can raise a constantly decaying Sg.

Since Sg is always going down, we can depict this as a sequence where the bullet is overstabilized at the muzzle, then fully stable and finally stable. And if we extend the range enough, the final stages will be under stabilized to ending NOT stable at all. This of course assuming we are considering an Sg in the "safe range", usually 2.0 or about.

The point here is we cannot have tight groups from unstable bullets so looking at the Sg alone, can be a good and pretty simple analysis to easily show that the "sleeping theory" is pure non-sense and groups are always larger as range increases and they can never shrink down.

It's also noted that measuring groups in angular units can be highly misleading, despite the culture we are used to, try for linear measurements, results will be normalized and the "sub" qualifier dismissed for good.

 

[one shot ST]

2 more groups with my .375 CT, cutting edge 320 gr H1000 134 and 135 gr, OAL 105 mm, foggy day temperature 7 C, good standard deviation less then 2 m/s, MV AVG 990 m/s




primers shape very good, probably 2 more gr in the next test



4 shots groups, the 3rd shot was on the right, my mistake, but 3 in one hole..

 

[one shot ST]

Frank, explain something to me. There are three groups here; are they all at the same distance?

I notice something here that bothers me in the first two groups, and that is vertical stringing. . Worse in the second group than the first, possibly due to barrel fouling or different shooting technique. The third group is a triangle/round shape, but the bulletholes are arguably not round. Was this third group the same load as the first two, and fired at the same distance? Why was it so different in shape than the first two?


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all the groups was fired at the same distance ( 100 meters ) the first 2 groups from a bench seated position, 2 different load and 2 different shooter, this during barrel brake in, Krieger suggest this procedure, and I did, after every shoot bolt removed, cleaning ecc ecc...... so not the best to check groups.

the third groups was with a different powder, prone position

and I've also did yesterday the last 2 groups ( post above ) prone position with different bullet and powder, in the next few days I'll check this load till 1800/1900 meters...

 

[wadcutter]

I think that people here are not thinking quite outside the box with regard to this question. Don’t be stuck thinking about bullet stability as in this case I think the answer lies with the barrel.

In F-Class and Small Bore shooting this type of phenomenon is quite well known. That is why some shooters use barrel tuners.

The barrel oscillates as the bullet travels down and out the bore. The point at which a bullet exits the bore will effect where it lands on a target. It is quite possible for a slower bullet to exit the bore at a point in the oscillation cycle that results in the slow bullet hitting higher on a close target than a faster bullet.

At longer distance the flight path of these bullets will then cross. And so the group will be tighter at long range than at close range. This is nothing new and is quite well known in precision target shooting.

When you talk group size at distance it pays to think of breaking the groups up into their vertical and horizontal components.
The Horizontal component is a combination of the rifles accuracy dispersion and wind drift variations. The same goes for the vertical component of the group however this part of the mystery is also effected by gravity!

Here is where a barrel tuner comes into play. By changing the position of the tuner it is possible to change the frequency of the barrels oscillation cycle. Then you can tune a load for a particular distance. Another method is to change seating depth.

So if you are having larger groups at shorter range and smaller groups at longer range then thank your lucky stars. Your particular load is in perfect tune for long range.

 

[secondofangle]

I asked this question because I was told it by a DTA person.

I've got 100 or so rounds through mt DTA 375CT now. The DTA 352 CE shoots pretty good like 1 MOA, the CheyTac factory SMK shoots unbelievably well less than 0.5 MOA at 3150 FPS.

BUT YESTERDAY I tried some of the CheyTac factory ammo with THEIR 350 grain copper solid "balanced flight projectile" and it was shooting HORRIBLE like 3-4 MOA at 100 yards.

Coukd be the shooter. But if anybody is near SLC and wants to show me how to shoot these under 1 MOA at any yardage, contact me and we'll make a trip to the range.

This is the point of the OP. MY inclination would be to say screw the copper solids (I wanna hunt at ELR with this gun in addition to shooting steel and paper). Which I'll probably do since I just got 500 SMKs to load. But if I believed the "drowsy bullet fallacy" I might be inclined to screw around with those CT solids some more and see how they do at 1000 yards. But that would be quite expensive a diversion with this cartridge.

 

[CowboyBart]

I didn't read the whole thread. That being said this has happened to me - with one particular rifle. My 264 WM will shoot 1" @ 100y, 1" @ 200y, and 1.4" [MENTION=89035]300[/MENTION]y.
I agree with LowLight that it is MENTAL. When I see 3 or 4 holes close together I always pull the 4th or 5th shot. When I can't see the size of the group it turns out to be a 1/2 MOA group.

 

[Graham]

Please explain how a bullet can "go to sleep" and get more accurate at longer...

I didn't read the last post, but there was this one time....?

 

[George63]

I didn't read the last post, but there was this one time....

was the one time at band camp?