So in my persute of a 1000 yd load, I would like to hear from the experts about the signs of bullet instability. My first question is where I can only shoot out to 200 meters at this time, will I see keyholing at this distance ? Does the instability grow more pronounced as the bullet travels greater distances ? I'm not going to be able to test at 600 yds until next spring.
Bullet "instability" question
- Thread starter Road_Clam
- Start date
If you're talking about rotational stability, this will show with inaccuracies at even short distances. To find out if your bullet will "stabilize" in you barrel at your velocity, you can use one of the online calculators. Berger has one on their site. In my limited experience, an unstable bullet will be in inaccurate bullet. Doubt you'll see complete key holing like in the attached pic, but your hole will favor one side.
If you're talking about a bullet staying supersonic at 600 or 1000 yards, you can use a ballistic calculator to give you a good idea. I've attached a pic of a target where a bullet went subsonic. This might be what you're referring to. I doubt you'll see this extreme at short distances.
Hope this helps.
If you're talking about a bullet staying supersonic at 600 or 1000 yards, you can use a ballistic calculator to give you a good idea. I've attached a pic of a target where a bullet went subsonic. This might be what you're referring to. I doubt you'll see this extreme at short distances.
Hope this helps.
Attachments
road-clam are looking for someone to shoot your rifle for you also? I mean come on,This has only been hashed over a million times on this Forum if you want to shoot 1000 yards get a 6mm Dasher or a 300 WSM! Now all you need is a good smith and you are good to go, Really I'm not lying.
Joe Salt
Joe Salt
CatShooter
FTRinPA said:
Being super sonic or subsonic has nothing to do with anything - there are guys shooting at 3,000 yds and doing very well at it.
The "Trans-sonic zone turbulence" is a myth that is easily proved with shadow-graphs. It is impossible for the bullet to pass through any sonic turbulence.
Bullets can hit sideways way above the speed of sound.
50gr 224 bullet, 14" twist, MV = 3,500.
Target is at 100 yards - impact velocity is ~3,200.
CatShooter said:FTRinPA said:
Being super sonic or subsonic has nothing to do with anything - there are guys shooting at 3,000 yds and doing very well at it.
The "Trans-sonic zone turbulence" is a myth that is easily proved with shadow-graphs. It is impossible for the bullet to pass through any sonic turbulence.
Bullets can hit sideways way above the speed of sound.
50gr 224 bullet, 14" twist, MV = 3,500.
Target is at 100 yards - impact velocity is ~3,200.
The "Trans-sonic zone turbulence" is a myth? I guess then I wasted 4 years getting my Aerospace Engineering degree??? There are bullets that handle the transition well, and those that don't. There are other reasons a bullet will keyhole, but the turbulence created when going transonic is a big one.
Ask a Navy pilot if he believes in the "Transonic myth"?
skiutah02
Silver $$ Contributor
Catshooter,
The pic is awesome. I am surprised to see that a projectile can turn sideways in that short a distance without a major problem with a barrel (besides apparently poor rotational stabilization). Not doubting the pic, but surprised.
If only I could get my projectiles to do that with accuracy, I would definitely get more points at 1000.
The pic is awesome. I am surprised to see that a projectile can turn sideways in that short a distance without a major problem with a barrel (besides apparently poor rotational stabilization). Not doubting the pic, but surprised.
If only I could get my projectiles to do that with accuracy, I would definitely get more points at 1000.
CatShooter
FTRinPA said:CatShooter said:FTRinPA said:
Being super sonic or subsonic has nothing to do with anything - there are guys shooting at 3,000 yds and doing very well at it.
The "Trans-sonic zone turbulence" is a myth that is easily proved with shadow-graphs. It is impossible for the bullet to pass through any sonic turbulence.
Bullets can hit sideways way above the speed of sound.
50gr 224 bullet, 14" twist, MV = 3,500.
Target is at 100 yards - impact velocity is ~3,200.
The "Trans-sonic zone turbulence" is a myth? I guess then I wasted 4 years getting my Aerospace Engineering degree??? There are bullets that handle the transition well, and those that don't. There are other reasons a bullet will keyhole, but the turbulence created when going transonic is a big one.
Ask a Navy pilot if he believes in the "Transonic myth"?
Well, actually, I did.
Lieutenant Colonel Mark S. Spencer, was a good friend of mine, and a U-2 pilot, and adviser in the 1991 war for Kuwait.
You can read about him here:
http://www.fas.org/irp/program/collect/u2ds/part07.htm
He said that there is no shaking, vibration or turbulence... just a lessening of ""G" force acceleration (being shoved back in your seat) as you increase above the speed of sound.
If you have ANY knowledge of aerodynamics, you will know that as a bullet slows, the front compression wave gets less and less as the projectile approaches ~1085 fps... but the bullet can not pass through the wave because it is always on the tip... as it continues to go slower, the compression wave just plain disappears at 1085, as the bullet slips below 1085. There is NEVER a time when the bullet passes through any turbulence.
The tail turbulence is ALWAYS behind the bullet and attached to the tail.
Do not forget the wind tunnel guys, they will be surprised to learn about this myth also.FTRinPA said:CatShooter said:FTRinPA said:
Being super sonic or subsonic has nothing to do with anything - there are guys shooting at 3,000 yds and doing very well at it.
The "Trans-sonic zone turbulence" is a myth that is easily proved with shadow-graphs. It is impossible for the bullet to pass through any sonic turbulence.
Bullets can hit sideways way above the speed of sound.
50gr 224 bullet, 14" twist, MV = 3,500.
Target is at 100 yards - impact velocity is ~3,200.
The "Trans-sonic zone turbulence" is a myth? I guess then I wasted 4 years getting my Aerospace Engineering degree??? There are bullets that handle the transition well, and those that don't. There are other reasons a bullet will keyhole, but the turbulence created when going transonic is a big one.
Ask a Navy pilot if he believes in the "Transonic myth"?
CatShooter
T-REX said:
Just what does that mean??? Nothing!
Just EXACTLY, what is the "trans-sonic zone", where is it, how is it formed, exactly where is the turbulence, how does the bullet pass through it, and how does it effect the bullet's flight - and if it does, then how do people shoot accurately past that zone?
It is easy to throw words around that you heard someone say on the internet... it a damn lot harder to actually have to explain them.
Inquiring minds want to know.
Catshooter,
Tell Col Spencer "thank you for your service". I'm curious what your background is and what qualifies you to make the statements you're making. Do yourself a favor and google "bullet turbulence" then tell me ALL the turbulence is BEHIND the bullet. All you have to do is look at the pictures. I hate it when people get into pissing contests on this site, as I like to leave that to the liber-tards. But I don't think you could be more incorrect in your statements.
If you have any scientific proof to backup your claims, please send me a link, as I would love to take a look at them. I am not foolish enough to think I know everything.
Tell Col Spencer "thank you for your service". I'm curious what your background is and what qualifies you to make the statements you're making. Do yourself a favor and google "bullet turbulence" then tell me ALL the turbulence is BEHIND the bullet. All you have to do is look at the pictures. I hate it when people get into pissing contests on this site, as I like to leave that to the liber-tards. But I don't think you could be more incorrect in your statements.
If you have any scientific proof to backup your claims, please send me a link, as I would love to take a look at them. I am not foolish enough to think I know everything.
Attachments
CatShooter
FTRinPA said:
I spent two years at Columbia University shooting small particles into helium and methane gasses. About 10,000+ shadowgraphs with high speed cameras (Red Lake Hi-Cams).
Nice pictures - they show NOTHING that will effect a bullet's flight. Just because there is a wave, it does not mean anything that will effect a bullet's flight.
CatShooter
FTRinPA said:
Ii did your Google... Look at the pictures yourself - the turbulence IS behind the bullet - what you are trying to pass off as turbulence, is the compression wave formed on the nose - that is NOT turbulence, and the bullet never passes through it.
There is a big difference - you do not know how to read and interpret shadow graphs.
[br]gstaylorg said:
CatShooter
CPorter said:
They are disruption waves - there is a lot of energy in nose waves, but very little in disruption waves.
CatShooter said:
In another life I worked at Arnold Engineering Development Center. I worked in rocket testing but had friends who worked in the wind tunnels. Most of the folks that I knew who worked in the wind tunnels are not longer living but one who is still living is a shooter so I called him and I asked him about what happens to a bullet when it goes from supersonic to subsonic. He said that the biggest thing that happens is the same thing that happens to an air plane wing and that is that the center of pressure moves and then there was a lot of description of what that does to the aerodynamics. He says that there is not a lot of turbulence and dynamics associated with this shift but it does not do anything positive for accuracy. This shift does not immediately cause bullets to tumble, that happens later in the flight path for different reason. So what I learned from this conversation is that the transition from supersonic to subsonic is not as significant as most folks claim and what I have been led to believe but still not a positive when accuracy is concerned. The problem we have in a public forum is that the idiots have the same voice as the geniuses and it is sometime difficult to know who is who. So when we ask for data or references we sometimes get bloviating and BS. So catshooter challenged my reply and that gave me reason to pursue a more rigorous response and I learned something in the process.
dmoran
Donovan Moran
More to the "myth"....
When the bullet flies supersonic, it compresses the air in front of itself, generating a series of shockwaves that origin from the bullet tip and propagate behind the bullet as a cone. Also, the center of pressure is located somewhere between the bullet tip and the center of gravity. Going downrange, the bullet loses its initial speed, due to drag, and reaches the “transonic region†when its speed reaches Mach 1.2. Going farther, it crosses the sound barrier at Mach 1, and then it exits from the transonic region when its speed falls below Mach 0.8.
When a bullet flies through the transonic region, the aerodynamics dramatically change. As we can see from the set of shadowgraph pictures FTRinPA posted above, the Transonic region shockwaves shift from the tip of the bullet backward to the tail as the bullet approaches and then crosses the sound barrier at Mach 1.
What happens in terms of ballistics and accuracy, is that the center of pressure shifts forward toward the tip of the bullet. The shifting of the center of pressure lengthen the lever between it and the center of gravity, amplifying static and dynamic instability. The result is that the bullet angle of attack and yaw might dramatically change, invalidating all the trajectory predictions made by ballistic software. It might also produce an increase in wobble, which can lead to an accuracy decay and can make the bullet tumble.
When the bullet flies supersonic, it compresses the air in front of itself, generating a series of shockwaves that origin from the bullet tip and propagate behind the bullet as a cone. Also, the center of pressure is located somewhere between the bullet tip and the center of gravity. Going downrange, the bullet loses its initial speed, due to drag, and reaches the “transonic region†when its speed reaches Mach 1.2. Going farther, it crosses the sound barrier at Mach 1, and then it exits from the transonic region when its speed falls below Mach 0.8.
When a bullet flies through the transonic region, the aerodynamics dramatically change. As we can see from the set of shadowgraph pictures FTRinPA posted above, the Transonic region shockwaves shift from the tip of the bullet backward to the tail as the bullet approaches and then crosses the sound barrier at Mach 1.
What happens in terms of ballistics and accuracy, is that the center of pressure shifts forward toward the tip of the bullet. The shifting of the center of pressure lengthen the lever between it and the center of gravity, amplifying static and dynamic instability. The result is that the bullet angle of attack and yaw might dramatically change, invalidating all the trajectory predictions made by ballistic software. It might also produce an increase in wobble, which can lead to an accuracy decay and can make the bullet tumble.
CatShooter
dmoran said:
That is not the nose wave moving back - that is impossible. The nose wave just fades wheen the bullet crosses 1085.
That is the tail negative wave that was there all the time, but once below the speed of sound, becomes more pronounced, because it starts to wrap around the edge of the base.
dmoran
Donovan Moran
CatShooter said:
It is a certainty of the effecting shockwaves, as the bullet (or any object in flight) slows into transonic and crosses to subsonic.
The effect it will have on a bullet, mostly depends on the bullets drag model/shape.
The real myth is your stating: "- is a myth" - and your twisting what I wrote (the Transonic region shockwaves shift), I said nothing of the nose wave moving back, that be your twist.
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