Transonic Cone Theory of Bullet Motion

[Kmahow2]

I've heard various reports over the years about claims that certain bullet gun combinations are more accurate at longer ranges & that some recover accuracy once they become subsonic. I had not read or seen any theory to support this. But some random musing whilst working up load data in Quickload & having read some of Brian Litz ballistic info on transonic effects, gave me an idea. So I started looking for supporting Cone Theory info & found this, which has some input from Brian Litz, which covers shorter distances;- https://www.researchgate.net/publication/224927152_A_Coning_Theory_of_Bullet_Motions

Transonic flight info;- https://www.accurateshooter.com/ballistics/transonic-effects-on-bullet-stability-bc

My idea is this.
A long (ELD) bullet travels for a distance/time until its velocity enters the transonic speed range (circa 1340-1120fps @ sea level), it continues to lose velocity & ultimately falls below the speed of sound. Now during the transonic phase, the centre of pressure moves back along the bullet, causing it to loose some of its stability, but its still spinning well above the gyroscopic stabilty minimums, thus wants to continue straight if possible. But outside effects are having an impact.

Now I have experienced this effect from a short barrelled 308 pushing 155 Scenars @2800fps, out to 900yds very accurate, at 1000yds shotgun groups. But interestingly, further analysis shows not shotgun (as in random) but rather in a circular dispersion or cone if you like, around the edge of the Black target centre. Obviously the bullet was losing stability, but most people think of this as a 2 dimensional effect (pitch/yaw), which it is, but its happening anywhere around a circle centered on the bullet.

This got me thinking about those reports of bullets getting accurate again past the transonic zone. Bear with me here. So if a bullet is flying along & then starts to destabilise, it does so in a circular motion, it could initially pitch up/down or yaw left/right, but the effect is fairly constant, anywhere in a circle. So if the bullet does NOT fully destabilise & tumble, the gyroscopic effect of its spin will recenter it like in the Cone Theory above & it should start to come back to the center of the circle. Unfortunately I don't have access ranges long enough to test this, nor tools to display the info in a visual format. But imagine Brians epicyclic motion image below on a larger scale as in the circle is perhaps a few feet across. Bullet motion in side on 2D ---------<cone>---- , cone of instability widens, then corrects at subsonic speeds.

This is just a theory for discussion

 

[_Windrider_]

There is an entire thread in this in here. @Jim Boatright is a member here.

 

[357Max]

So if the bullet does NOT fully destabilise & tumble, the gyroscopic effect of its spin will recenter it like in the Cone Theory above & it should start to come back to the center of the circle.

This defies logic. It may re-stabilize, but it has no memory of original point of aim. It will not come back to center. It will continue in stabilized fashion on it's new trajectory.

Some bullet designs do a good job of passing through transonic without altered trajectory. They may get some wobble & then tighten back up gyroscopicly without POI shift. In this case though they are always flying to the center of the circle albeit with slight variation in stability.
If the latter is what your trying to say then I'd agree with that.

I think it has a lot to do with what end of the bullet wobbles when it hits transonic. Think VLD vs. a more blunt nose design.

 

[jasent]

Bullets do not correct corse. They either stay on corse or don’t

Personally I run a faster twist than required, in some instances much faster. This seems to have several benefits. More stable through transition and better trace, more splash, full bc potential. Jmo

If the bullet of choice can’t handle the twist change your bullet. I’ve heard many folks say vld type bullets don’t transition well. I have never seen that with my shooting

 

[Kmahow2]

I'm thinking of a spinning top, they spin until they lose stability, but many times they will start to wobble & the rest point starts to describe a circle, then they half fall, then stand up & stabilise on the original spin point on the second destabilisation they usually fall over. I know it sound weird & counter intuative, but much in nature is so. If i had the range a selection of bullets to test I would. I'm now thinking of lower velocity loads to test the theory within the ranges I can use, so get the round subsonic by 500yds !

 

[Lowlight]

No...

The bullet is either stable or not, within the length of the turbulence that exits the bore, it does not get more stable later, none, no, not happening

You're a part of a long line people who believe this, and it has been proven false many times

 

[_Windrider_]

No...

The bullet is either stable or not, within the length of the turbulence that exits the bore, it does not get more stable later, none, no, not happening

You're a part of a long line people who believe this, and it has been proven false many times

Once the center of pressure moves behind the center of gravity it’s over. Bullet cannot restabilize.

 

[Lowlight]

The phenomenon people experience is personal, it's an internal issue on how we process information through our eyes

First off this almost always gets seen with Magnum calibers, that is their first clue it's them. Magnums cause people to flinch, so think about that flinch for a second.

When people shoot a magnum at 100 yards they fill the scope with a target. It's a wall of paper, so that object is right there. As they move out to distance, the field of view opens up and the sight picture is less in your face.

So what happens is the brain is reacting to what it perceives as being dangerous vs less dangerous. You flinch and shoot like crap at 100 yards, but then shoot better at 300 because the image is softer on the mind.

A lot of shooting is subconscious, it's the brain doing things we are not controlling. Same thing here it's your sight picture. If you reduce the power on your scope you can see the difference, there are several drills we can do that demonstrates how we process the information.

If you shoot bad groups at 100 and better groups at 300+ it's you, it's not the bullet, it's you. The relationship between your waking and subconscious mind is outta sync

 

[timintx]

The phenomenon people experience is personal, it's an internal issue on how we process information through our eyes

First off this almost always gets seen with Magnum calibers, that is their first clue it's them. Magnums cause people to flinch, so think about that flinch for a second.

When people shoot a magnum at 100 yards they fill the scope with a target. It's a wall of paper, so that object is right there. As they move out to distance, the field of view opens up and the sight picture is less in your face.

So what happens is the brain is reacting to what it perceives as being dangerous vs less dangerous. You flinch and shoot like crap at 100 yards, but then shoot better at 300 because the image is softer on the mind.

A lot of shooting is subconscious, it's the brain doing things we are not controlling. Same thing here it's your sight picture. If you reduce the power on your scope you can see the difference, there are several drills we can do that demonstrates how we process the information.

If you shoot bad groups at 100 and better groups at 300+ it's you, it's not the bullet, it's you. The relationship between your waking and subconscious mind is outta sync

Don't hate me Frank lol but I have visually seen the bullets corkscrewing wildly a few times with fully qualified bullets and ultimately still hits within the group at longer ranges ,one example was at the 1000yd nationals when vapor trails were really showing up in detail , so much so that I could actually see the air spinning from the rifling on the bullet. 8 of the shots had a steady flow or v flowing smooth;y and then I saw 2 corkscrewing wildly out of ten shots . I just knew the 2 would be out of the group . They were not as the guy shot 4.5 Inch 10 shot group. From what I have seen the bullets are flying around the original flight path and comes in to it as the bullet settles down , I know these were still corkscrewing out to 800 yds or so from what I could tell, I have created it with some goofy baffling in my suppressors as well but lost no accuracy down range when it sucked at 100yds[3 inch group averages] . Then immediately go to 1000yds ,hit the clay pigeon dead center into 3 pieces and then with the next three shots hit all 3 pieces , These are not because of bad bullets but more of muzzle blast disturbances. I think this is what I think people are seeing but not knowing for sure without seeing the corkscrewing of Epicyclic swerve. but I can say I have visually seen the effect especially with funky baffling in my suppressors.

Tim in Tx

 

[jasent]

Perception isn’t always correct. Like frank said if you think it’s happening it’s happening. May not be reality but our mind believes it.

They are either stable or not

 

[Lowlight]

Tell Bryan Litz he will pay you to prove it

He posted shoot thru targets this week on Facebook demonstrating groups at 100 and 300

There is an active reward, your swirl buzzword is microscopic you can’t see it

You saw wind …

 

[oneshot.onehit]

Don't hate me Frank lol but I have visually seen the bullets corkscrewing wildly a few times with fully qualified bullets and ultimately still hits within the group at longer ranges ,one example was at the 1000yd nationals when vapor trails were really showing up in detail , so much so that I could actually see the air spinning from the rifling on the bullet. 8 of the shots had a steady flow or v flowing smooth;y and then I saw 2 corkscrewing wildly out of ten shots . I just knew the 2 would be out of the group . They were not as the guy shot 4.5 Inch 10 shot group. From what I have seen the bullets are flying around the original flight path and comes in to it as the bullet settles down , I know these were still corkscrewing out to 800 yds or so from what I could tell, I have created it with some goofy baffling in my suppressors as well but lost no accuracy down range when it sucked at 100yds[3 inch group averages] . Then immediately go to 1000yds ,hit the clay pigeon dead center into 3 pieces and then with the next three shots hit all 3 pieces , These are not because of bad bullets but more of muzzle blast disturbances. I think this is what I think people are seeing but not knowing for sure without seeing the corkscrewing of Epicyclic swerve. but I can say I have visually seen the effect especially with funky baffling in my suppressors.

Tim in Tx

see ya in Kansas soon, should be fun that we are being pushed to 4200 yards.

cheers

 

[Newbie2020]

but I have visually seen the bullets corkscrewing wildly

How did you see bullets corkscrewing wildly? High speed camera? Post the footage and you’ll have believers.

 

[Kmahow2]

I'm not talking about close range shots, only post transonic behavior.

With the right lighting, you can see bullets fly, we think they are fast but compared to light they are pedestrian. I've watch 50cal bullets shot at targets at 1500yds through high power binoculars mounted on a tripod & if the lighting angle is right you can clearly see the bullets fly & sometimes they do corkscrew along. I was shooting 208eldm's at 200yds the other week, with a low morning sun on a windless day. I was trying to determine if they would stabilise at subsonic velocity & check if they stayed that way at the target. I could see them fly at 1050fps in a nice arc to reach the target & the target crew reported all holes were calibre size, round & subsonic. Next test will be transonic perfomance, by loading them to 1500fps & see what happens over distance.

 

[timintx]

I'm not talking about close range shots, only post transonic behavior.

With the right lighting, you can see bullets fly, we think they are fast but compared to light they are pedestrian. I've watch 50cal bullets shot at targets at 1500yds through high power binoculars mounted on a tripod & if the lighting angle is right you can clearly see the bullets fly & sometimes they do corkscrew along. I was shooting 208eldm's at 200yds the other week, with a low morning sun on a windless day. I was trying to determine if they would stabilise at subsonic velocity & check if they stayed that way at the target. I could see them fly at 1050fps in a nice arc to reach the target & the target crew reported all holes were calibre size, round & subsonic. Next test will be transonic perfomance, by loading them to 1500fps & see what happens over distance.

sorry I misread.

 

[timintx]

How did you see bullets corkscrewing wildly? High speed camera? Post the footage and you’ll have believers.

Mirage and vapor trails at matches , I could see them clearly . anybody that has seen vapor trails long enough eventually you will see it too . I will try to find a video of this corkscrewing and post it , there are white paper reports out on it as well using angled flash hiders. There are quite a few over the years mostly varmint hunters videos.

 

[_Windrider_]

Mirage and vapor trails at matches , I could see them clearly . anybody that has seen vapor trails long enough eventually you will see it too . I will try to find a video of this corkscrewing and post it , there are white paper reports out on it as well using angled flash hiders. There are quite a few over the years mostly varmint hunters videos.

The corkscrew of a vapor trail is the effect of the wind breaking off the surface. Ever seen a vortex of an aircraft wingtip? Same same. It’s not corkscrewing.

 

[timintx]

Tell Bryan Litz he will pay you to prove it

He posted shoot thru targets this week on Facebook demonstrating groups at 100 and 300

There is an active reward, your swirl buzzword is microscopic you can’t see it

You saw wind …

Not wind as I shot a number of tiny groups without the suppressor .Bryan does not want to hear what I have to say , there are different levels of this corkscrewing effect but even if it is microscopic at the time you can still see a vapor trail swirling like a bottle rocket . I dont really care to argue with Brian and to be honest most is proprietary to Sellars Ballistic Technologies. I can create the effect though suppressor baffling but this effect is rare in most cases happens on average 1 out of 50 times with a regular open muzzle . The problem is we could not figure out what specifically caused this especially with a standard regular muzzle and fully qualified bullets ,,so it is hard to reproduce but have seen it , i was shocked that the 10 shot group came back really small just like anybody else but this was back in 2008 or so. since then I have seen the effect countless times and in videos as well. I speculated back then it has to be the muzzle blast disturbance with a combined cross flow component of some kind , years later suppressor baffling created that same effect except really bad and noticeably large at 100 yards . Bryan just has not created the effect so it does not exist, which is totally understandable, but dont discount a effect if he has not seen it or can produce the effect. How about this Frank , I would rather reproduce it for you, , I want you to believe me more than Bryan anyway lol. You are welcome to a demo any time. just say the word.

 

[timintx]

The corkscrew of a vapor trail is the effect of the wind breaking off the surface. Ever seen a vortex of an aircraft wingtip? Same same. It’s not corkscrewing.

Problem with that theory is the other 8 bullets in that group showed smooth laminate flow, no corkscrewing.

 

[Feniks Technologies]

Tag…..

 

[iceng]

This effect ? There is still a centre line the bullet travels on.
If you saw the corkscrew effect, it is an optical illusion.

That or you are playing computer games.

 

[Sandow the Heretic]

Not wind as I shot a number of tiny groups without the suppressor .Bryan does not want to hear what I have to say , there are different levels of this corkscrewing effect but even if it is microscopic at the time you can still see a vapor trail swirling like a bottle rocket . I dont really care to argue with Brian and to be honest most is proprietary to Sellars Ballistic Technologies. I can create the effect though suppressor baffling but this effect is rare in most cases happens on average 1 out of 50 times with a regular open muzzle . The problem is we could not figure out what specifically caused this especially with a standard regular muzzle and fully qualified bullets ,,so it is hard to reproduce but have seen it , i was shocked that the 10 shot group came back really small just like anybody else but this was back in 2008 or so. since then I have seen the effect countless times and in videos as well. I speculated back then it has to be the muzzle blast disturbance with a combined cross flow component of some kind , years later suppressor baffling created that same effect except really bad and noticeably large at 100 yards . Bryan just has not created the effect so it does not exist, which is totally understandable, but dont discount a effect if he has not seen it or can produce the effect. How about this Frank , I would rather reproduce it for you, , I want you to believe me more than Bryan anyway lol. You are welcome to a demo any time. just say the word.

So as spotters there are things we see that are odd. Sometimes they are explainable and sometimes they are not. My home range has four very different wind conditions between the firing point and 2100 yards. Mild wind shielded by the mountain, strong wind from a valley, mild wind from the next mountain then moderate wind from the open plain. The result is that bullets regularly have a corkscrew appearance in flight. That is a macro effect that in this case is explainable by relatively simple topology. When it comes down to corkscrewing at the micro level which is the case in this thread, the physics cannot be perfectly modeled or observed but there are aspects that can be. As the tech has gotten better, the truth is that most of them are now observable between doplar and high speed video. The radar studies (and not just AB) show that bullets with marginal stability will undergo a certain amount of oscillation and that the air does damp that (within limits) due to drag effects. As has been pointed out though, once that oscillation has been damped, the direction is not going to realign with the bore. The bullet will stabilize along a random direction within a cone of accuracy based upon how extreme the oscillation was to begin with.

In ELR, this can happen twice. After leaving the bore and after the destabilizing transition back to subsonic. In both cases you can have a bullet that is stabilized in flight but no longer going quite the right direction.

Bullets that are unstable from go, suck. Bullets that can't transition to subsonic and retain the same direction are good up to a point and then suck. Bullets that behave predictably all the way are what win competitions in this game.

However you want to call the "bullets goes to sleep" theory, it is a horse that has been beaten for so long passed dead that we are just wailing away on vulture crap at this point. The basic physics and the observed data says this theory is simply untrue.

-Alex

 

[Feniks Technologies]

Pretty easy to test bullets corkscrewing “wildly”.

Shotmarkers or plastic/paper shoot through targets along the trajectory.

All are relatively cheap and you can make the entire internet eat crow with your results…..

 

[acudaowner]

super sonic cone

 

[timintx]

This effect ? There is still a centre line the bullet travels on.
If you saw the corkscrew effect, it is an optical illusion.

That or you are playing computer games.

View attachment 7869835

It very well may be an illusion as to diameter of the cone ,but when I am comparing the corkscrewing to laminate flow side by side and they still hit close you have to wander why , then years later while experimenting with suppressor baffle design can not shoot better than 3 inches at 100 and tack drives at 1000 10 minutes later , then go back to 100 and 3 inch groups.

 

[iceng]

Years ago i got some old polystyrene fruit boxes, set them 1 meter apart, and placed them at multiple ranges up to 700ish meters. Only doing 100m and the end distance... Bullet drop and all.

I got a paint pen and coloured one side of a loaded bullet. Shot it and made note. This did 2 things. Measured group sizes, and measured spin decay.

The 2 boxes at 700m i could see the paint marks, and because they were 1m apart, and knew velocity, i could measure the spin decay for a set distance.

Also, group sizes at 100m and 700m were identical.

Rude experiment but helped me learn about twist rates.

 

[timintx]

Pretty easy to test bullets corkscrewing “wildly”.

Shotmarkers or plastic/paper shoot through targets along the trajectory.

All are relatively cheap and you can make the entire internet eat crow with your results…..

just telling my experiences , you can take it or leave it , I am not selling anything . just trying to help .

 

[Ledzep]

The only things I've ever seen corkscrew are tracers (shifting CoM) and bullets with really bad eccentricities on aero surfaces (ogive or boat tail).

 

[Feniks Technologies]

just telling my experiences , you can take it or leave it , I am not selling anything . just trying to help .

You’re the one telling everyone you have a company with proprietary things, patents on contraptions that “turn” off compensation, have seen things that a rocket scientist with doppler who the Chief Ballistician for Berger bullets can’t duplicate or figure out.

But when it’s time to put the proof on the table, you’re just “trying to help.”

 

[_Windrider_]

It very well may be an illusion as to diameter of the cone ,but when I am comparing the corkscrewing to laminate flow side by side and they still hit close you have to wander why , then years later while experimenting with suppressor baffle design can not shoot better than 3 inches at 100 and tack drives at 1000 10 minutes later , then go back to 100 and 3 inch groups.

The term is laminar not laminate. And eventually it becomes a turbulent zone and that’s what creates the twist

 

[timintx]

Years ago i got some old polystyrene fruit boxes, set them 1 meter apart, and placed them at multiple ranges up to 700ish meters. Only doing 100m and the end distance... Bullet drop and all.

I got a paint pen and coloured one side of a loaded bullet. Shot it and made note. This did 2 things. Measured group sizes, and measured spin decay.

The 2 boxes at 700m i could see the paint marks, and because they were 1m apart, and knew velocity, i could measure the spin decay for a set distance.

Also, group sizes at 100m and 700m were identical.

Rude experiment but helped me learn about twist rates.

Is it possible when you tested the corkscrewing may not have been present when you tested? I have shot through yaw cards within 50 yards , much easier to align and had the same exact results as well many times at the time there was no suspected problems or issues, just curious if they corresponded and they did ,but when there is a problem the same target test may not show the same result . I have not done a multi paper test with this suppressor in particular because of time constraints so the next quickest thing was to shoot 100 yds averaging 3 inch groups, now if it were just dispersion it should be horrible spreading out at 1000 . if it is coning it should settle down by 1000 yards ,but it is literally tack driving at 1000, then reconfirm at 100 yds ,still 3 inch groups. By all indications the baffling is causing this effect and it absolutely shoots well under 3 MOA at 1000 yards.

 

[timintx]

You’re the one telling everyone you have a company with proprietary things, patents on contraptions that “turn” off compensation, have seen things that a rocket scientist with doppler who the Chief Ballistician for Berger bullets can’t duplicate or figure out.

But when it’s time to put the proof on the table, you’re just “trying to help.”

Never said that about Brian. He is probably the one person who could , and yes trying to help.

 

[iceng]

I placed foam targets at 700ish meters (was like 715, was a few years ago). I aligned my dope to hit the target. I placed a paper target at 100m in my sight path and shot a group.

The group size at 100m and 700m were identical. As a bonus, i had colours which i could use to calculate how mcuh the bullet rotated from one box to the next.

My theory is corkscrew does not exist, which it was not present. My theory is "corkscrew" is an optical illusion, thus can not be readily measured.

Its mirage. The target doesnt "wobble" side to side, the target is stationary. Our perception of it is wobble.
Corkscrew is is this. Optical illusion. Unless someone with a physics degree and high level ballistics education can explain it otherwise, i cant prove anything further because i dont know what to test or look for.

 

[timintx]

So as spotters there are things we see that are odd. Sometimes they are explainable and sometimes they are not. My home range has four very different wind conditions between the firing point and 2100 yards. Mild wind shielded by the mountain, strong wind from a valley, mild wind from the next mountain then moderate wind from the open plain. The result is that bullets regularly have a corkscrew appearance in flight. That is a macro effect that in this case is explainable by relatively simple topology. When it comes down to corkscrewing at the micro level which is the case in this thread, the physics cannot be perfectly modeled or observed but there are aspects that can be. As the tech has gotten better, the truth is that most of them are now observable between doplar and high speed video. The radar studies (and not just AB) show that bullets with marginal stability will undergo a certain amount of oscillation and that the air does damp that (within limits) due to drag effects. As has been pointed out though, once that oscillation has been damped, the direction is not going to realign with the bore. The bullet will stabilize along a random direction within a cone of accuracy based upon how extreme the oscillation was to begin with.

In ELR, this can happen twice. After leaving the bore and after the destabilizing transition back to subsonic. In both cases you can have a bullet that is stabilized in flight but no longer going quite the right direction.

Bullets that are unstable from go, suck. Bullets that can't transition to subsonic and retain the same direction are good up to a point and then suck. Bullets that behave predictably all the way are what win competitions in this game.

However you want to call the "bullets goes to sleep" theory, it is a horse that has been beaten for so long passed dead that we are just wailing away on vulture crap at this point. The basic physics and the observed data says this theory is simply untrue.

-Alex

Alex , is there a way to calculate the diameter of the specific cone diameter at a given distance throughout the trajectory?

 

[Sandow the Heretic]

Alex , is there a way to calculate the diameter of the specific cone diameter at a given distance throughout the trajectory?

Cone as in the supersonic wake? Sorta but It is also going to change based upon conditions and not just velocity. Plus it is going to move around on the bullet as you see here and there are multiple simultaneous shock waves. You would have to pick a semi-arbitrary point to call the end of the wake but you could simply shoot a velocity series in front of a shadowgraph set up. So calculate? probably not worth the CFD time but determine? Sure. Why though?

-Alex

 

[timintx]

Cone as in the supersonic wake? Sorta but It is also going to change based upon conditions and not just velocity. Plus it is going to move around on the bullet as you see here and there are multiple simultaneous shock waves. You would have to pick a semi-arbitrary point to call the end of the wake but you could simply shoot a velocity series in front of a shadowgraph set up. So calculate? probably not worth the CFD time but determine? Sure. Why though?

Cone as in the supersonic wake? Sorta but It is also going to change based upon conditions and not just velocity. Plus it is going to move around on the bullet as you see here and there are multiple simultaneous shock waves. You would have to pick a semi-arbitrary point to call the end of the wake but you could simply shoot a velocity series in front of a shadowgraph set up. So calculate? probably not worth the CFD time but determine? Sure. Why though?

-Alex

-Alex

Sorry Alex what I meant was the diameter of the coning motions or the circular error as it would be on a target.

 

[Sandow the Heretic]

Sure. Put the gun in a vise, shoot a statistically significant number of rounds at a paper target and measure the distance from each shot to the center of the group (not necessarily the point of aim). That will give you the cone of accuracy for that load in that gun under those conditions. Do that at a few ranges and you can then report out accuracy as a box and whisker plot. Normal prediction would be that the box would increase in MOA as distance increases and at the subsonic transition probably by quite a lot.

If you want the circular error for an individual bullet then you can measure it with radar but every real bullet will have differences based upon the lateral offset of the CG relative to the centerline of the bullet. No bullet is perfect though some are certainly worse on average than others. You can then add on piles of different effects from the atmosphere and barrel/muzzle interaction. I'm not sure what you get out of that that is of practical use. The average and sd of that error is useful though.

As far as the coning theory in general, I think there are limitations that are mostly glossed over. The shape of the bullet will determine how it is effected by drag and thus how forces push it into alignment in flight. Not every bullet shape or weight distribution will necessarily be pushed into nose leading procession. It also kinda doesn't matter for the most part. If a bullet oscillates in a nose out procession (and my guess is that short nosed bullets are likely to do this), as long as it does that every time it will fly predictably.

-Alex

 

[timintx]

Sure. Put the gun in a vise, shoot a statistically significant number of rounds at a paper target and measure the distance from each shot to the center of the group (not necessarily the point of aim). That will give you the cone of accuracy for that load in that gun under those conditions. Do that at a few ranges and you can then report out accuracy as a box and whisker plot. Normal prediction would be that the box would increase in MOA as distance increases and at the subsonic transition probably by quite a lot.

If you want the circular error for an individual bullet then you can measure it with radar but every real bullet will have differences based upon the lateral offset of the CG relative to the centerline of the bullet. No bullet is perfect though some are certainly worse on average than others. You can then add on piles of different effects from the atmosphere and barrel/muzzle interaction. I'm not sure what you get out of that that is of practical use. The average and sd of that error is useful though.

As far as the coning theory in general, I think there are limitations that are mostly glossed over. The shape of the bullet will determine how it is effected by drag and thus how forces push it into alignment in flight. Not every bullet shape or weight distribution will necessarily be pushed into nose leading procession. It also kinda doesn't matter for the most part. If a bullet oscillates in a nose out procession (and my guess is that short nosed bullets are likely to do this), as long as it does that every time it will fly predictably.

-Alex

Thank you for that info , as others have suggested it could be an illusion as to intensity , and I have no doubt the science says it is very small but my research within suppressor baffle design has led me to the question and that is why I asked.

 

[brianf]

been reading some of the posts a few times, and i think im following..

@timintx .. few questions in you have a min

you suggest the bullet is corkscrewing out of your proprietary suppressor baffle design because of 3 moa at 100 and matching groups size of top tier suppressors (TBAC etc) at 1000.

consistent moa or less, is what i consider tack driving at 1000 all things considered

do you believe the radius of the corkscrew is decaying at a linear rate, or is there a particular range/RPM that the reduction in radius/group size occurs?

is the corkscrew a constant variable.. every round shot
low at 50
left at 75
high at 100
200, 300, 400, 500
etc

or do you believe it is random once it leaves the nuzzle yet always stays within the 3 MOA circle

was the 3 MOA group centered around the POA or was it "off to one side" of POA, as there is wobble "on the corkscrew" track

if what you think and have seen though the glass is actually happening, we should be able to take the same rifle/ load and shoot at several distances with a predetermined location /group size off the point of aim...

or am i missing it

thanks

edit.. added a few words for clarity

 

[timintx]

been reading some of the posts a few times, and i think im following..

@timintx .. few questions in you have a min

you suggest the bullet is corkscrewing out of your proprietary suppressor baffle design because of 3 moa at 100 and matching groups size of top tier suppressors (TBAC etc) at 1000.

consistent moa or less, is what i consider tack driving at 1000 all things considered

do you believe the radius of the corkscrew is decaying at a linear rate, or is there a particular range/RPM that the reduction in radius/group size occurs?

is the corkscrew a constant variable.. every round shot
low at 50
left at 75
high at 100
200, 300, 400, 500
etc

or do you believe it is random once it leaves the nuzzle yet always stays within the 3 MOA circle

was the 3 MOA group centered around the POA or was it "off to one side" of POA, as there is wobble "on the corkscrew" track

if what you think and have seen though the glass is actually happening, we should be able to take the same rifle/ load and shoot at several distances with a predetermined location /group size off the point of aim...

or am i missing it

thanks

edit.. added a few words for clarity

That is hard to say, and is what I am trying to determine. Many years ago at the matches while spotting for shooters I see 2 bullets that corkscrews and the other 8 do not yet they hit tight downrange . In the case of suppressor testing I have I have only the beginning of the trajectory and the end of the trajectory for reference. Here is what led me to believe it was corkscrewing on the suppressor testing . While ladder test graphing the barrel moments at 100 yds for positive compensation which had been working fine for modifying the patterns and seeing the changes with each adjustment towards the last graph upon setting up the final pattern I had the pattern almost perfect. The remaining problem was the poi change when the suppressor was put on , which was 3 inches left when installed. I needed 0 poi change for the contract request which is a tall order in itself. The particular baffling was a offset clipped style baffling and reasonably quiet, When the baffling was modified to correct the poi change essentially blowing the bullet to the right in the can before exit it caused a random large dispersion , could not see the graphs at all due to a huge dispersion, I knew the weight was right for the suppressor weight to it should be tuned at least ,but now it was not shooting well at all really throwing shots out at 100 yds. So with my nominal single powder charge I shot 3, 5 shot groups for an average size of 3 inches . It had just shot 3 tiny 5 shot groups that worked out to 2 holes touching without the suppressor but with it now it was dispersing around the point of aim almost equally in a random pattern 1.5 inches for the aim point. So before I scrapped that design I was curious to see if it was linear downrange suspecting corkscrewing . I was shocked to say the least that it was not linear . I could not believe it so I went back to 100yds and shot another group and it was horrible, right at 3 inches . When I shot at 1000yds I got lucky and hit a clay pigeon dead center , broke it into 3 equal parts then with the next 3 shots broke those 3 parts , every part was hit and shattered to dust. Shortly after the crosswinds picked up bit I decided to put up some paper anyway and shoot 3, 5 shot groups at 1000 ,all shots were waterline level within a half of an inch and 5.1 inches was the widest group. So in conclusion the particular baffling created dispersion close to the gun but should have been linear down range and was not, not even close to linear. Intermediate and internal ballistics are my field of study and am not a external ballistics scholar but there is always more to learn and just trying to learn what I need to complete my studies particularly with muzzle influences on flight in this case . Alex has helped with that in the past as well and am grateful for that . As a result I have a design that is complies with the contract now with minimum poi change with tight groups on both ends trajectories with one powder charge and low ES and SD.

 

[brianf]

That is hard to say, and is what I am trying to determine. Many years ago at the matches while spotting for shooters I see 2 bullets that corkscrews and the other 8 do not yet they hit tight downrange . ...

Ok still tracking …just going to chop it up a few times because there is a mix of testing and theory inside

Also, there will be a bunch of questions that may cross between theory and proprietary info, so answer what you can without “slipping”..dont want to cause trouble if you have other entities involved.

So previously you had seen 2 out of 10 “bullet trace” look different in flight but they were still in a tight group, but you didn’t have a reason/theory yet.


During testing for positive compensation:

From what I had always read positive compensation only really showed up at distance because the trajectory difference of velocity at 100 was almost impossible to separate from possible bullet irregularities and environmentals.

I know short range BR guys dont even weigh powder, they volume dump at the bench because velocity differences don’t really show up.

How did you induce the variables for the 100 yard testing, different charge, seating depths?

Were you able to compensate for those “standards”, and bring the POI inside/tight which is actually “outside” the expected groups from those different loads?

Im thinking if several loads expected POI partially overlap then its luck of the draw/ possible if they converge to the same POI even without compensation?


Modifying patterns..:

What or how much positive compensation had you been seeing at 100, or better yet what velocity differences were you using/ targeting as your variables (I would think the weapon, components, location, POA, etc are the static variables).

The suppressor was the right weight…:

That must be a formula; I have not seen a calculation for a tuner weight which in theory is what the suppressor is acting like…as you suggest it “should be tuned” or im off base?

I would think that calculation includes, barrel material, barrel length, bore size, OD, profile at a minimum.

Is the suppressor a clip on or a screw on?

If the suppressor should be of correct weight, you also must have calculated the exact position of the suppressor when attached as the exact location is part of setting up a tuner.

If the exact attachment point is calculated, was the suppressor able to be “moved” fore and aft for tuning?

I’d think with the tuners on the market that adjust/move a few .001”s when adjusting.. how was that accomplished or the suppressor was designed with best case scenario and load development was “going to bring it home”?


Downrange:

So, after the suppressor killed your dreams at 100 (lol) you shot it farther (1000) and the instead of the groups being 30” / 3MOA they were tac driving..with suppressor on correct?

Did you try the same ammo at 1k without suppressor for a quick base line of what the rifle and load could actually do?

Would be great to know if the load/rifle was capable of “clay bird” at 1k without suppressor, then we would know suppressors effect at 1k, if nothing else.


Final design:

You believe that by redesign you have made a “proper” suppressor which has limited effects on accuracy compared to the original un-suppressed rifle or that’s still on going


Sorry if long winded, trying to make it so I can follow your answers properly and not ask doubles.


Thanks

edit..ill check spelling AGAIN a little later..Iphone

 

[Fig]

Take this sleeping bullet shit over to Accurateshooter where they believe in bullshit gun myths like this. It's been categorically disproven. The busts on Litz's methodology are invalid. His results were conclusive, and no one has a greater body of evidence about transonic/subsonic projectiles at termination.

My 6X47 goes transonic before 1,500 yards, and far from stabilizing the SMK 107s become tumbling musket balls. At 1,400, IMPACT, IMPACT, IMPACT, and at 1,500 miss low, miss right, miss high, miss left. They go from inside a large pizza tin, to wildly all over the place from only a 100 or so FPS difference.

The idea that somehow they would stabilize makes no sense to me, and defies my personal experience. Nowhere in the natural world does such a thing occur...

IMO the only valid theory for what happens to transonic bullets is:

 

[_Windrider_]

Take this sleeping bullet shit over to Accurateshooter where they believe in bullshit gun myths like this. It's been categorically disproven. The busts on Litz's methodology are invalid. His results were conclusive, and no one has a greater body of evidence about transonic/subsonic projectiles at termination.

My 6X47 goes transonic before 1,500 yards, and far from stabilizing the SMK 107s become tumbling musket balls. At 1,400, IMPACT, IMPACT, IMPACT, and at 1,500 miss low, miss right, miss high, miss left. They go from inside a large pizza tin, to wildly all over the place from only a 100 or so FPS difference.

The idea that somehow they would stabilize makes no sense to me, and defies my personal experience. Nowhere in the natural world does such a thing occur...

IMO the only valid theory for what happens to transonic bullets is:

One of the primary reasons it’s all bullshit is. Bullets are spin stabilized. Just like velocity, the spin immediately begins to reduce the second it leaves the muzzle. Once the rotation reaches its critical point the bullet is dead. You cannot spin it back up and restabilize it. What you can hope for is that bullet reaches the point as after max ord when it’s already coming down and hope that it stays on a predictable path. If it happens before max ord you’re gonna miss by long ways

 

[Sandow the Heretic]

One of the primary reasons it’s all bullshit is. Bullets are spin stabilized. Just like velocity, the spin immediately begins to reduce the second it leaves the muzzle. Once the rotation reaches its critical point the bullet is dead. You cannot spin it back up and restabilize it. What you can hope for is that bullet reaches the point as after max ord when it’s already coming down and hope that it stays on a predictable path. If it happens before max ord you’re gonna miss by long ways

They certainly don't ever spin faster once they are in flight but the bullet spin rate slows down pretty slowly. It only has to overcome surface drag and whatever rotational inertial is bled off by destabilization events. Even for longer range shots, they impact with the vast majority of the rotational inertial they had at the muzzle.

A good demonstration of this is firing bullets that can make the transition into subsonic and still remain predictable. If you fire the same bullet at just under the speed of sound it will usually just tumble because it is spinning slower than it would having left the muzzle at three times that speed and then flown for a few seconds. Subsonic loading is a PITA lol...

-Alex

 

[_Windrider_]

They certainly don't ever spin faster once they are in flight but the bullet spin rate slows down pretty slowly. It only has to overcome surface drag and whatever rotational inertial is bled off by destabilization events. Even for longer range shots, they impact with the vast majority of the rotational inertial they had at the muzzle.

A good demonstration of this is firing bullets that can make the transition into subsonic and still remain predictable. If you fire the same bullet at just under the speed of sound it will usually just tumble because it is spinning slower than it would having left the muzzle at three times that speed and then flown for a few seconds. Subsonic loading is a PITA lol...

-Alex

If the formula is correct it decays pretty rapidly. A bullet fired at 3000 fps in an 8 twist. Barrel has an rpm of 270000. At subsonic (1200fps). It’s a mere 107000. That’s more than 50% of its spin and more than 50% of velocity. This obviously varies from bullet to bullet but that thing is becoming rapidly unstable, especially if it’s still going up

 

[Sandow the Heretic]

If the formula is correct it decays pretty rapidly. A bullet fired at 3000 fps in an 8 twist. Barrel has an rpm of 270000. At subsonic (1200fps). It’s a mere 107000. That’s more than 50% of its spin and more than 50% of velocity. This obviously varies from bullet to bullet but that thing is becoming rapidly unstable, especially if it’s still going up

Why would you assume that the forward velocity and the rotational speed drop at the same pace? They are tied to each other at the muzzle but not past it.

-Alex

 

[Ledzep]

Yeah once the rifling is no longer present the 1:8" twist guarantee expires.

 

[_Windrider_]

Why would you assume that the forward velocity and the rotational speed drop at the same pace? They are tied to each other at the muzzle but not past it.

-Alex

Do we have technology capable of measuring Down range spin rate or a mathematical formula to calculate it? The assumption is that they are linear because to my knowledge we have no other way to measure it that I know of. Multiple factors depend on its decay like drag parasitic or induced, the size of the meplat perhaps BC etc etc etc. I’m willing to be wrong. The broader point being is that a bullet doesn’t go to sleep and wake up. And doesn’t start stable become unstable then stable again. It only goes from stable to unstable because it’s stability depends on velocity and spin.

 

[Ledzep]

Yes, there are multiple ways to pick up rate of twist down range with doppler, video, etc... In fact to get proper doppler drag data from "down-loaded" ammo to get lower mach regimes, guys will often enough use faster-than-normal twist barrels to simulate the correct rotational speed of a down-range projectile.

As far as bullets being good, going wonky, then getting good again-- off the cuff I'm going to say not likely. Very not likely. I'm more inclined to think that once a bullet goes trans-sonic and gets kicked off on some wayward trajectory, it's going to stay on that trajectory. It's stability may be temporarily compromised by buffeting or uneven shockwave(s) and then eventually come back in to stability, but the trajectory will not "find home" again.

 

[Secant]