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

[secondofangle]

I've heard this over many many years, but it's coming up more frequently in discussions of solid copper and brass projectiles.

Can anybody explain this physically?

The only thing I can think of is that it's leaving the bore travelling in a conical spiral pointed downrange, and as it goes further, it gets closer to the center of the spiral?

Any other thing would seem to me to cause random variability that would not improve as distance increases.....

 

[Sako man]

Google epicyclic swerve.

At some point rotational inertia (gyroscopic) along the long axis of the bullet stabilizes the projectile. As the theory and observation goes some rifles are more accurate at longer ranges so thus groups are tighter at longer distances vs. closer distances based on radial measurements.

 

[BERTMAN77MK2]

I have experienced this with certain rifles before but did not understand why. Thanks Sako man

 

[0311 Hesco]

This is a can of worms. I say this because epicycle swerving happens, but so does the Coriolis effect, as does the Poisson Effect; but you don't dial left or right for that. Epicycle Swerving is argued to be "one of those" effects. Even ballistician Brian Litz agrees it's there, however so minute, the average or above average.....scratch that, nobody accounts for it. The bigger picture here, is the problem incurred by angular error compounding. Not sure if that is a real term, but what I'm going for here is whatever is an issue at 10', it will be 10 times worse at 100. You can argue the whole 'it can be seen on a spinning top' thing, but there are so many outside variables on that, it's really just incorrect. Surely an argument will ensue with things like, 'well you dumb young punk, I've been accounting for epicycle swerving for 30 years and you're wrong'. My reply is this, 'keep on then, and better restock on SpinD as well.'

Someone have a link to a prior thread on this?

 

[Greg Langelius *]

I believe in worrying about the things I can make an improvement on; otherwise, I'd never get any sleep.

So instead, I ask what can be done about it, rather than how this insurmountable whatchamacallit exists and why. If there's no way to 'fix' it anyway, I move on to the things I can actually do something beneficial about. This may not sound important to you now, especially if you are young. But when you get to be an elder fart like me, not wasting one's time on ultimately pointless mental exercises begins to have a more compelling appeal. One may even wish one had adapted to said conclusion far earlier, maybe even...

Shoot the rifle, note its performance characteristics, learn how to make it work to its/your best; and above all, try never to piss into the wind...

It would be easy to accuse me of thinking a lot; but for me, there are still limits on that. Even so, I'm almost certainly thinking too much, but not about this.

Greg

 

[Graham]

There are many, many threads on this same topic right here on Sniper's Hide.

The misunderstanding probably stems from the fact that the longer a bullet is in flight the more rotational twist it needs to rotate smoothly around its rotational center. But that doesn't mean that the same bullet leaves the muzzle in an unstable condition and later becomes stable, which is not the case.

 

[Jaeger308]

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

It can not. There are two types of stability you need to understand gyroscopic and dynamic go do some homework on these, Brian Litz's book Applied ballistics for long range shooting would be a great place to start. Overly simply put, a bullet's stability needs to fight the force applied between its center of gravity (located toward the rear of the bullet) and a calculated point called the center of pressure (located toward the front of the bullet) this CP is where outside forces converge and as force magnitudes and bullet velocity change so does this points location. A bullet is least stable right out of the muzzle as it bleeds velocity it becomes more stable, I think this is where this term "a bullet goes to sleep" comes from. However if a bullet's flight path is effected or changed early in its flight it will stay on that course or direction altering POI's although it will become more stable on its way to the target.

 

[Graham]

A bullet is least stable right out of the muzzle as it bleeds velocity it becomes more stable, I think this is where this term "a bullet goes to sleep" comes from. However if a bullet's flight path is effected or changed early in its flight it will stay on that course or direction altering POI's although it will become more stable on its way to the target.

Again: Either a bullet is stable when it leaves the muzzle, or it isn't.

 

[Jaeger308]

Again: Either a bullet is stable when it leaves the muzzle, or it isn't.

Yes there is a minimum stability a bullet needs in order to have a happy flight, the standard is the Miller stability factor number. A bullet need a minimum Miller number of 1.4-1.6 out of the muzzle. A bullet bleeds velocity a lot faster than RPS of rotation, hence stability or rigidity of axis grows down range. If an under stabilized bullet leaves the muzzle it will not work well, also over stabilized can effect bullet axis trajectory tracking or tracing degrading BC and increase drag down range. This degrading is rather small in the whole picture.

 

[Graham]

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

If an under stabilized bullet leaves the muzzle it will not work well, also over stabilized can effect bullet axis trajectory tracking or tracing degrading BC and increase drag down.

Again: Either a bullet is stable when it leaves the muzzle, or it isn't.

Bullets don't have Miller numbers.

 

[secondofangle]

Maybe I should rephrase:

Do you believe that a rifle can shoot say 3 MOA at 100 yards but 0.5 MOA at 1000?

And if the answer is yes, how can that be, and are the arguments above an explanation?

If the answer is yes it can happen, this has implications for load development, right? Because testing at 100 yards may not be representative.

 

[Graham]

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

Maybe I should rephrase:

Do you believe that a rifle can shoot say 3 MOA at 100 yards but 0.5 MOA at 1000?

And if the answer is yes, how can that be, and are the arguments above an explanation?

If the answer is yes it can happen, this has implications for load development, right? Because testing at 100 yards may not be representative.

Loads that perform badly at short range don't magically become tack drivers at distance.

That myth came from the (true) idea that short, flat base bullets are best for short range accuracy while longer higher BC bullets are not as inherently accurate by design.

So Benchrest bullets that shoot well at short range will outperform VLDs for group size at that same distance; but the VLD, although it shoots worse at short range, will outperform the other bullets at long range.

But a 3 MOA load at 100 won't become a .5 MOA load at 1000.

And testing at 100 yards is rarely useful for anything but initial load development for accuracy node and seating depth anyway.

Here's what I do: When my load shoots well at 100, I try it at 300. Not all loads that are good at 100 shoot well at 300. When my load shoots well at 300, I shoot it at 600. Not all loads that shoot well at 300 shoot well at 600. But if the load shoots well at 600 it will probably shoot well at 1000.

"Well" at distance means not only maintaining it's relative accuracy, but low SD numbers and a low vertical spread on the target.

 

[Greg Langelius *]

Coming back to this, I believe Curt/Jaeger is right on the money, and Lowlight's comment simplifies this all most directly.

I would simply add that as velocity drains, and the trajectory really gets curved downward; the static (gyroscopic) stability force is still hard at work, while the dynamic(aerodynamic/weathervaning) force is at it weakest. Effectively, this means that the bullet does not 'nose down' to realign its rotational axis with the line of trajectory anywhere near as effectively as when it had most of its muzzle velocity. Seen from the target end, the bullet's impact hole appears somewhat like a keyhole, but the nose end of the impression still points up, while the additional drag from the pitch relative to the trajectory increases overall drag and increases drop, often dramatically. I have tested this at 1000yd, and the effects I observed support the theoretical part of my comment. This is a good reason why the best twist rate at longer distance is usually the least twist that will still stabilize the bullet at the shorter distance.

Remember, gyroscopic forces only drop a little over the trajectory, but aerodynamic forces can only begin to work once the bullet leaves the muzzle, may take a few instants to have any real effect, and then diminish toward the point of irrelevance as the distances become extreme. At any rate, few times of flight exceed three or so seconds, so a lot has to happen very quickly for any effect to dominate very greatly.

Greg

 

[jolofree]

Again: Either a bullet is stable when it leaves the muzzle, or it isn't.

Bullets don't have Miller numbers.

Please explain what you mean by this. Do you mean that a specific bullet doesn't have a Miller stability rating factor associated with it, or assigned to it like a BC, until it's actually shot out of a specific twist rate rifled barrel, and then it 'gets' a stability probility factor based on rate of twist, along with other factors, to predict to some extent if it'll 'shoot' or not?

 

[Graham]

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

I mean that the Miller twist calculation is a mathematical formula, and that bullets are not assigned 'miller numbers' like they are assigned ballistic coefficients.

 

[Lowlight]

For every bullet that people claim shoots poorly at close distance, there is a guy hammering that same bullet into a single hole. It's a myth....

The shooter effects more than any epicycle swerve bullshit. That movement is microscopic and is not effecting groups. It's the mental aspect of being able to see your group vs not being able to see it which removes the shooter from the equation.

List me your sleeping bullet and I will put a box of factory ammo with it in 1 hole inside 100 yards. Cause what you are saying is, it shoots better at 300 than it does at 100 because it has to sleep... Great, I'm gonna hammer 10 inside 1 hole at 25 yards cause if it's not sleeping at 100 it's certainly wide awake at 25.

Its always people looking for a scientific excuse on why they don't shoot as good as they hoped. The scientific principle seen when these bullets don't do what the shooter hopes is called, Lackapractice.

 

[Toast]

I can't wait for turkey sandwiches tomorrow!! MMMMMMMm mmmmmmmm goooooood.

 

[0311 Hesco]

for ye who say the bullet will go to sleep and shoot better at distance. Do a thorough evaluation of the size of target you are shooting at. Like LL said its mental. There is a lot of truth to "aim small, miss small" I have found that shooting larger (read: bigger in the sight or scope) targets, my margin of error is greater. Try putting a 5, 3, 1, and .5 MOA target at 100 or any distance really, and see what the "bullet" does.

 

[Graham]

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

There is a lot of truth to "aim small, miss small" I have found that shooting larger (read: bigger in the sight or scope) targets, my margin of error is greater.

So, what you are saying is: Aim small, miss big, because the smaller the target the bigger the miss.?

 

[Lowlight]

Gee Bob, I thought you were a better shot than that... well Billy Joe, you see I am using 175s and not 168s so they don't go to Sleep until farther downrange. So you see, it's not my fault. Because of _______ (insert political excuse here) the gun shop didn't have any good bullets so I had to use these, hence the poor 100 yard group. If I was shooting at 800 yards this group would be much better, unfortunately our range only goes to 200 yards.

 

[MikeEzell]

Drag makes the bullet point into the wind most at peak drag...which is where is has the most velocity. Therefore, it is most affected near the muzzle.

 

[Strykervet]

I think this may be the first I've ever heard of a bullet "going to sleep". I've seen shooters go to sleep before.

I'm sorry, I have to agree with Graham here, I can't visualize a bullet that starts out with a wide MOA and then tightens up downrange. I can see how it can stabilize farther downrange however, but it should still have the same or similar MOA regardless.

One instance, a round can stabilize downrange is if the rifling twist and velocity and/or bullet size are out of proportion. In extreme cases, it can present itself a keyholes up close, but fine downrange as the bullet slows and stabilizes once the velocity and spin are in proportion. There's probably other instances too, but I can't envision any of them causing a better group farther downrange. If it starts out at 3MOA at 100, how's it gonna be 1MOA at 1000? I've never experienced it. I may shoot certain distances and positions better than others, but that's me, not the gear.

And who really cares anyway, I mean, like Lowlight said, there's much more important things to consider. And as long as you optimize the load to the weapon, it's really a non-sequitur.

 

[Graham]

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

Drag makes the bullet point into the wind most at peak drag...which is where is has the most velocity. Therefore, it is most affected near the muzzle.

You might want to re-think your basis for that conclusion: You need more information and you are missing at least one definition of drag.

 

[0311 Hesco]

[MENTION=7]Lowlight[/MENTION],
I think it's time for new product from the makers of SpinD: Red Bullet! it wakes your bullet up. It gives your bullet wiings!

 

[TOP PREDATOR]

don't take the term waking up as "a bullet gets better downrange", as described in the previous posts, just misused as describing a particular bullet's ability to outperform another bullet further out or at a faster / slower speed.

"waking up" is relatively saying that one bullet stays stabilized better than another bullet down range. it may actually suck throughout it's whole flight, but doesn't suck as much as the other bullet when further out due to a host of reasons. so though it seemed bullet A stunk at 200y vs. bullet B, bullet B may just not be as good performance wise as bullet A further out, giving the impression that bullet A somehow gets miraculously more accurate - all the while staying the same all along - just more consistent or "awake".

but a 4" group at 400 isn't going to shrink to 3" at 500. think of a quarterback throwing a wobbly bomb pass, it suddenly doesn't turn to a perfect spiral and remains a brick.

 

[Sako man]

Google epicyclic swerve.

At some point rotational inertia (gyroscopic) along the long axis of the bullet stabilizes the projectile. As the theory and observation goes some rifles are more accurate at longer ranges so thus groups are tighter at longer distances vs. closer distances based on radial measurements.

I will state again.

To clarify in looking at my first quote, it's a theory and an observation. That said I agree with anyone who says it's possibly/probably the shooter. Epicyclic swerve is a real occurrence but may or may not contribute to inverse radial measurements.

 

[gunrunner]

I had a Rock River Arms 24" barreled AR15 varmint rifle with a 1/8 twist. With 69 grain Sierra match bullets, it shot much smaller groups past 300 yards than it did inside of 300 yards.

 

[0311 Hesco]

I had a Rock River Arms 24" barreled AR15 varmint rifle with a 1/8 twist. With 69 grain Sierra match bullets, it shot much smaller groups past 300 yards than it did inside of 300 yards.

No it didn't. It was the shooter, not the gun. I will bet a paycheck that if you remove shooter error from behind the gun, it will not "shoot smaller groups past 300 than inside 300"

 

[Pinecone]

First, what measure of the group being smaller at a longer range?

If absolute group size (inches) I can't see that happening. As someone else said, a 4" group at 400 yards is not going to become a 3" group at 500 yards.

But if you are talking MOA size of the groups, I can see that happening. The assumption is that the bullets path is either a cone shaped spiral or that it leaves and flies such that for each increase in distance the angular distance off center stays the same, ie, 1 MOA at 100 yards is 1 MOA at 500 yards.

But looking at the football analogy, a not perfectly thrown pass may be traveling in a more of a cylindrical spiral, with some divergence due to distance, but not a fully linear divergence. So that at 100 yards you have a 1 MOA (1.047") group, but at 500 yards you have a .75 MOA (3.9") group. Absolute group size is larger, but angular size is smaller.

 

[Greg Langelius *]

I think we're attributing less credit to random chance than it may deserve. A single group of 3, 5, or more shots is just that, a single sample. Accuracy is about consistency, and I think it takes a fair number of such samples before any realistic inferences may be made regarding a load's effective accuracy. I doubt I could reliably determine a competition load from a single group.

The COF in our semi-monthly club matches provides four scoring targets of ten shots apiece, and that's my load development test. It presents more than just a cherry picked sample of two from which to make any determination. It subjects the development load to nothing less than/different from the intended application; with the same stresses, restrictions, concentration, and random adversity all the subsequent examples of the application the load must face.

It's a very slow process, with testing possible only twice monthly. But it's also as stringent and reliable a test as I can devise. The score tells the story, and there are four scores to average out.

There are too many uncontrollable variables at work to make very 'good' dispersions representative of any aspect of accuracy. The target we use requires a 1 MOA dispersion to clean the target, and ties are settled with the half-MOA V-Ring.

Once a trend is established on the first target, the chips really go down.

Some may look at a 'bad' first target, and just go through the motions for the other three. Or; others will buckle down and eke out the very best score that's still possible. Such conditions reinforce determination and character, as well as just accuracy.

This is where the ability to stage a comeback, and the ability to persevere even when perfection has been shot dead in its face finds their origins.

It is at times like these that the human factor in all shooting situations becomes most obvious.

We may concern ourselves with matters like epicyclical wobble and its like; but in the big picture, it's far too late to worry about such individual factors once the chips are down. You get what you brought can deliver, and the only real remaining variable is the shooter.

You do the best you can with what you have, however the chips get distributed. If the shooter can do this, their performance is assured from the moment they step onto the range, regardless of how that first flier takes the wind out of the sails. If not, then random chance becomes the determinant.

If things like epicyclical wobble take center stage, it's mainly going to be because random chance put all those other small 'noise' issues to sleep, not the bullet. Every shot is prevailing in the face of whichever factor(s) random chance has lent its whim. All groups will exhibit dispersion, this is why, and its also why no specific group size is truly representative of absolute performance.

It is also why a consistent score on our club's match target is my goal, and not some individual five round group. I hope for a 1 MOA average, and know that no matter what, there will pretty much always be the random leaker(s). It's random chance that has the final say.

For those who fire but a single shot, any failure to see the projected impact as anything smaller than a circle of probability is really wishful thinking. The best any computation of individual factors can provide is that compounded/collective circle of probability. One may believe they can call the shot to within fractions of MOA, but the rifle and nature know better.

In all of this, epicyclical wobble is just another singer in the chorus, and the shooter is the featured performer.

I know that my criteria and technique may appear to be undemanding and overly simplistic, but in the end, both my expectations and outcomes will usually fall within my definition of decently reliable performance. One MOA at 100yd and two MOA at 1000yd means an acceptable hit probability circle to me.

Once I got my 1000yd F Open game together, "9"s were my definition of leakers, and "8"s my definition of flyers.

"7"s and lower were awcraps. When things got that bad, I knew the primary malfunctions were taking place within my brain housing group. These were things I was missing, and not the rifle.

Could a rifle shoot one particular MOA value of dispersion at a given range, and another, smaller one further out? Sure, but my guess would be that the farther, smaller one was another product of random chance. Each shot encounters randomly different combinations of influences, so they might randomly produce a smaller dispersion.

If it occurred on a regular basis, I'd be checking scope parallax. For example, fixed parallax scopes are usually optimized for parallax at 200yd for riflescopes, and 50yd for pistol scopes. So a set of rifle groups of 1MOA at 100yd, and 1/2MOA at 200yd could easily be the product of parallax. For a variable parallax scope, the distance of the smaller group could occur wherever the effective parallax is set.

Greg

 

[0311 Hesco]

y'all are putting too much into this. if it were a spin stabilized ROCKET, sure well talk about this Epicyclic crap. This is a projectile that has no other propulsion after it leaves the barrel. the bullet is dumb and will go which ever way it was pointed in. It's the nut behind the bolt that makes the shot size differ 99.999999999999999999% of the time. period.

"But looking at the football analogy, a not perfectly thrown pass may be traveling in a more of a cylindrical spiral, with some divergence due to distance, but not a fully linear divergence. So that at 100 yards you have a 1 MOA (1.047") group, but at 500 yards you have a .75 MOA (3.9") group. Absolute group size is larger, but angular size is smaller."

NO. That is still ALL shooter. Put a piece of paper at 100 and then at 500 and shoot thru both of them. 1MOA is 1MOA at 100 AND 500. If you are shooting smaller groups at farther distance, THE SHOOTER IS THE AFFECTOR.

 

[Diablo]

The first time I heard the myth about the bullet "going to sleep" and performing better at longer distance was back in the 90's when I called Sierra with a concern about why a particular lot of .338 MKs was not shooting well.

That was also the last time I called Sierra about anything.

 

[40xs]

Any of you guys ever play with a toy gyroscope as a kid. You wrap a string around the shaft and then pull it off fast and set the gyro on the floor and watch it do all sorts of weird stuff as it gradually slows down. Sometime it stablizes early, sometimes it stabilizes later.

 

[Gunfighter14e2]

Can anybody explain this physically?

Unless you have a parallax issue it is most always seen, with boat-tail bullets. Ask yourself why does this not happen with flat base projectiles?
A weapon that will do this (save a scope issue) seems to only do this until it is crowned correctly. Remember at bullet body exit the tail is still in the bore, hence should there be any very minor crown issue, this is where it will show up first. All this is based on a quality projo, seconds or culls that seem to make there way into retail do not count. Should you question this, scratch ever so gently the transition from base to body. Witness the mark on the brass, install in battery starting at 1200 hrs then shoot a full clock by the hr and watch what happens. US Army has been down this road many times, starting in 40's.

 

[Graham]

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

Unless you have a parallax issue it is most always seen, with boat-tail bullets. Ask yourself why does this not happen with flat base projectiles?

Ummmm:

One can see bullets go to sleep, if they are boat tail bullets, provided you don't have a parallax issue?!!

Or do you mean you can see boat tail bullets group better at distance?!

Or do you mean something else?

And flat based bullets don't have an epicyclic swerve unless the rifle is crowned incorrectly?!!

Hmmmmm..... Just when I thought this Thread was done.

 

[Gunfighter14e2]

Graham

The sleep issue is always with boat-tails or step downs. Many shooters don't understand many scopes, have 0.1 - 1moa+ of parallax even when the ret and target are crystal clear to them. Hence the need to do the head-bob drill behind the glass for every range when shooting groups for score. Many scopes will have the target just off the perfect to your eye setting, when all of the plx is gone. Many wonder why some days they shoot better groups than others, same ammo, gun & range. Tolerance stacking then add a lighting change and it's a real group/s chase with new shooters.

If you have the ability to re-crown or are re-barreling, change the crown ever so slightly and shoot a B/T & F/B group at 100 then 300 or better.

 

[gstaylorg]

Parallax is by far the most likely cause of people shooting smaller (angular) groups at longer range than at short range. Parallax error potentially has a much larger effect at close range than at long range; however, it has nothing to do with flat-based vs boattail bullets. A shooter having parallax issues could produce smaller groups at longer distance than at shorter distance regardless of the type of bullet used.

 

[psinclair]

Parallax is by far the most likely cause of people shooting smaller (angular) groups at longer range than at short range. Parallax error potentially has a much larger effect at close range than at long range; however, it has nothing to do with flat-based vs boattail bullets. A shooter having parallax issues could produce smaller groups at longer distance than at shorter distance regardless of the type of bullet used.

Winner!^^^^^^

Bullets shooting better at distance than up close would be the same as saying Nolan Ryan would have more strikeouts if he pitched from second base than the pitcher's mound......

 

[WRM]

We had a passionate discussion on this subject many years ago on the Accurate Reloading Forums - when I read that Chapter in Brian's book I got the impression that he was aware of that discussion, and agree with his conclusions. I'm surprised that no one has posted a link to "How Bullets Fly" site ( How do bullets fly? ).

To me, this appears to be an example of convergence - "going to sleep"? http://www.nennstiel-ruprecht.de/bullfly/fig18.htm

However, that is "yaw", not bullet path/trajectory....

I think of group size as a cone, or more likely, a divergent cone - a trumpet bell being an exagerated example. Once a projectile strays from "nominal" trajectory, there is no inherent force that brings it back. It would take an external input/force to bring it back, and it's just not there....

As mentioned above, would have to shoot two targets at varying distances simultaneously, have less angular divergence at longer distance, and I have $100 that says no one can "Sho-Me" that....

Cheers,

Bill

 

[hlee]

Winner!^^^^^^

Bullets shooting better at distance than up close would be the same as saying Nolan Ryan would have more strikeouts if he pitched from second base than the pitcher's mound......

Maybe not with a standard fast ball, but with a Gyroball - Wikipedia, the free encyclopedia, who knows...

Technically, the quoted analogy would more aptly equate to putting more balls in the strike zone- which does not necessarily equate to getting more strikeouts...

 

[40xs]

Same hand and same arm throwing the ball,,,but no consideration to the ball, itself? (just as important )!!

 

[Sterling Shooter]

This "sleeping" concept can be put aside, without any consequence to the aspiring marksman. While a marginal understanding of external ballistics may be useful for a shooter to recognize the need to adjust sights for a given distance, or to realize that at some point the bullet will begin to fly erratically and eventually tumble end over end, the only thing from all of this discussion which I believe to be meaningful is don't shoot more bullet than needed to reach the target nose-on. I could shoot VLD's at SR and get a fabulous result but recoil is greater with these bullets and thus the need to perfect my position from shot to shot becomes more important. Since I can get the same result at short range shooting a flat base bullet that weighs a lot less and can be fired in a loading producing less recoil, I see that less can indeed be more. Of course, if LR performance is the end game then you shoot what bullet is needed to get there, for example, a 175 rather than a 168 in a .308. At any rate, spending time on this topic is not going to lead to any discovery other than to know to abandon the advice of anyone who promotes the "going to sleep" notion as a reason for any result.

 

[E. Bryant]

...the only thing from all of this discussion which I believe to be meaningful is don't shoot more bullet than needed to reach the target nose-on.

That's fine for punching holes in paper, but what if we actually expect the bullet to do something useful once it reaches the target?

 

[Sterling Shooter]

Then you might want to explore terminal ballistics

 

[0311 Hesco]

This topic is detracted. For all intents and purposes, the bullet DOES NOT "go to sleep". Work on the fundamentals and ensure your rifle is set up correctly. Oh yea, and get off the internet and GO SHOOT. perfect practice makes perfect.

 

[zenbiker]

"Going to sleep" = stabilizing gyroscopically in flight.

The fight path of a bullet is not a 'straight line'. It actually follows a movement know as 'precession' where the bullet actually spirals around the intended flight path.

Due to number of variable which include but are in no way limited to barrel twist, muzzle velocity, type of rifling, construction of the bullet. powder burn rate, neck tension and other factors ad nauseum, the radius of this precession, i.e, the deviation from actual line of flight, and therefore intended point of impact, varies during bullet flight. it is very common for certain bullets, especially high aspect ratio bullets ( bullets that are longer by several multiples of their diameter, generally regarded as high ballistic coefficient, low drag, long range projectiles) to precess, or 'wobble' more when leaving the muzzle, leaving befuddled shooters with seemingly large groups at 100 yards, but as the gyroscopic forces on the bullet stabilize, the precession radius becomes smaller, and consequently groups at longer ranges may not only be smaller in terms of MOA or MILs, but actually in size as well compared to 100 yard groups. Berger VLDs, among other excellent low B.C. projectiles, are known to exhibit ths seemingly contradictory flight characteristic.

A very good comparison that has been used to explain this is a simple child's toy top. When first set to spinning by whatever mechanism, the top tends to wobble at first, then settles into a smooth, almost noiseless rotation stabilized by its gyroscopic nature. Then, as the top rpm drops, it begins to wander again, becoming very wobbly indeed until it falls over. This is not completely unlike what happens to a bullet as it passes through the transonic transition to subsonic flight, albeit the latter is exceedingly more complex.

In short, referring to a bullet "going to sleep" refers to the bullet attaining desirable gyroscopic stability in flight after leaving the rifle's barrel. This can occur in as little as 20 yards to as much as 200 yards or more, and makes the shape of a group, not its actual size, the primary indicator of a particular load's accuracy. A load that forms up a predictable round group at 100 yards is generally more desirable than a group that is smaller in size but irregular in shape (note, this is my experience only and will likely generate a great deal of discussion regarding my mother's choice of footwear, the likelihood that I was in fact dropped on my head during birth, and the effect of flourescent lighting in my developmental years). I hope this removes someof the murk surrounding this topic, and best of luck to you.

Wes



Sent from my iPad using Tapatalk HD

 

[steve123]

"Going to sleep" = stabilizing gyroscopically in flight.

The fight path of a bullet is not a 'straight line'. It actually follows a movement know as 'precession' where the bullet actually spirals around the intended flight path.

Due to number of variable which include but are in no way limited to barrel twist, muzzle velocity, type of rifling, construction of the bullet. powder burn rate, neck tension and other factors ad nauseum, the radius of this precession, i.e, the deviation from actual line of flight, and therefore intended point of impact, varies during bullet flight. it is very common for certain bullets, especially high aspect ratio bullets ( bullets that are longer by several multiples of their diameter, generally regarded as high ballistic coefficient, low drag, long range projectiles) to precess, or 'wobble' more when leaving the muzzle, leaving befuddled shooters with seemingly large groups at 100 yards, but as the gyroscopic forces on the bullet stabilize, the precession radius becomes smaller, and consequently groups at longer ranges may not only be smaller in terms of MOA or MILs, but actually in size as well compared to 100 yard groups. Berger VLDs, among other excellent low B.C. projectiles, are known to exhibit ths seemingly contradictory flight characteristic.

A very good comparison that has been used to explain this is a simple child's toy top. When first set to spinning by whatever mechanism, the top tends to wobble at first, then settles into a smooth, almost noiseless rotation stabilized by its gyroscopic nature. Then, as the top rpm drops, it begins to wander again, becoming very wobbly indeed until it falls over. This is not completely unlike what happens to a bullet as it passes through the transonic transition to subsonic flight, albeit the latter is exceedingly more complex.

In short, referring to a bullet "going to sleep" refers to the bullet attaining desirable gyroscopic stability in flight after leaving the rifle's barrel. This can occur in as little as 20 yards to as much as 200 yards or more, and makes the shape of a group, not its actual size, the primary indicator of a particular load's accuracy. A load that forms up a predictable round group at 100 yards is generally more desirable than a group that is smaller in size but irregular in shape (note, this is my experience only and will likely generate a great deal of discussion regarding my mother's choice of footwear, the likelihood that I was in fact dropped on my head during birth, and the effect of flourescent lighting in my developmental years). I hope this removes someof the murk surrounding this topic, and best of luck to you.

Wes



Sent from my iPad using Tapatalk HD

That's a much better way of explaining it than I could have given.

For the nay sayers... Buy yourself a $$$$ 375 Cheytac and shoot some Jamison/Hooker 350 grain solids through it. What you'll find out after about $1000 of expended ammo is that the rifle will shoot like sh!t at 100Y and you'll be able to hit stuff you never thought you'd be able to at ELR distances.

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.

As the years went by, and although I didn't shoot the rifle all that much, I shot some very small groups out to 2500Y on steel and not just a few times either. Some of which were witnessed by friends. The most memorable was a 5" 3 shot group at 2050Y.

Here's some groups. First is at 1450Y with the small splats being the 375CT, big splats are my 30-375 with 240's. BTW the 30-375 is a .3" shooter at 100Y.


This one was at 1000Y/ 2 groups of 4 rounds testing seating depth with 330gr Lehighs which still didn't shoot but 1" at 100Y.
<a href="http://s411.photobucket.com/user/shmonty03/media/DSC00119.jpg.html" target="_blank"><img src="http://i411.photobucket.com/albums/pp195/shmonty03/DSC00119.jpg" border="0" alt=" photo DSC00119.jpg"/></a>

This one at 2500Y, too be honest my friend and I were both shooting each our own 375 rifles. Suffice it to say it was easy to hit this plate for both of us. Oh, this was at the bottom of the plate and the sideways hit was a bounce off the ground.

 

[Lowlight]

Yawn,

This has already been discussed, it's the "HUMAN FACTOR" it happens especially with magnums.

The shooters is effected by the sound and recoil, and mostly the sight picture of the target being at 100 yards. They are blown around and it appears to be erratic. Yet shoot a target farther aways an all those effects seems to disappears and the shooter is much more calm, and relaxed shooting the heavy magnum. Then magically the groups get better.

Our brains are complex, we are the driving force behind good accuracy. If we mess with that in a way our brain doesn't like it causes accuracy issues. Magnums are the biggest offenders with some people. It's simple to test. Blind start a person off at 1000+ yards with a target and note their reaction, then move them to 100 yards and see the difference.

Stable is stable it either works or it doesn't. There is no pilot to steer the bullet back to target. Misunderstanding this does not change it, nor does pointing to something else. If the holes at 100 yards were round it is stable. Otherwise they would have been oblong

 

[steve123]

Yawn,

This has already been discussed, it's the "HUMAN FACTOR" it happens especially with magnums.

The shooters is effected by the sound and recoil, and mostly the sight picture of the target being at 100 yards. They are blown around and it appears to be erratic. Yet shoot a target farther aways an all those effects seems to disappears and the shooter is much more calm, and relaxed shooting the heavy magnum. Then magically the groups get better.

Our brains are complex, we are the driving force behind good accuracy. If we mess with that in a way our brain doesn't like it causes accuracy issues. Magnums are the biggest offenders with some people. It's simple to test. Blind start a person off at 1000+ yards with a target and note their reaction, then move them to 100 yards and see the difference.

Stable is stable it either works or it doesn't. There is no pilot to steer the bullet back to target. Misunderstanding this does not change it, nor does pointing to something else. If the holes at 100 yards were round it is stable. Otherwise they would have been oblong

I see what you are saying but I've got pretty good form. I will say that I have won the only ELR match I've ever shot with my 30-375R shooting against 50's and 338's. I've won few long range championships as well. Do you think I had poor follow through, flinching or bad form when I shot those groups on those plates???

Russ, that developed the loads for the DTI HTI in 375CT has discovered the same phenomenon. Could it be that he can't shoot either???

I fully understand that unless a person has experienced this phenomenon it is hard to believe. If this had only happened a few times then maybe I'd chalk it up to human error but the rifle shot well at distance "and poorly to 200Y". I don't expect the critics to believe me and that fact doesn't bother me in the least.

 

[Lowlight]

@steve123
Simple question

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