stagpanther
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Move to another state.
Physics of shooting a rifle
- Thread starter tangolima
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I'm thinking about it for my retirement, if the good Lord allows me to see that day. We are still here for reasons that are beyond my control.
That's why I said my life is cursed. Always have to run from same sort of tyranny. Sadly I am running out of destinations and strength. Even more sadly, a lot of people, Americans included, don't understand why I have to keep running.
-TL
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stagpanther
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I have bad news for you--it never ends. We are free-range animals that live on tax farms.
I'll keep going, till I can't go anymore.
-TL
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Alright. I tried starting discussion on spring, but there seemed no interest, or it was drowned out by some other bigger talks. Let me try again in some other way.
From time to time, we need to reduce a coil spring's strength, to lighten a trigger's weight for instance. We were taught at gunsmithing school never to cut coils off. Instead we should thin the wire's diameter. In practice we often end up cutting coils because it is easier. Certainly both methods work in reducing the spring's strength.
What's the difference? Why gunsmiths are so adamant about cutting coils, even though at least sometimes they still choose to do it? There are even talks saying that cutting coils makes a spring stronger, not weaker. How comes?
-TL
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From time to time, we need to reduce a coil spring's strength, to lighten a trigger's weight for instance. We were taught at gunsmithing school never to cut coils off. Instead we should thin the wire's diameter. In practice we often end up cutting coils because it is easier. Certainly both methods work in reducing the spring's strength.
What's the difference? Why gunsmiths are so adamant about cutting coils, even though at least sometimes they still choose to do it? There are even talks saying that cutting coils makes a spring stronger, not weaker. How comes?
-TL
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stagpanther
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I'll bite--why is that?
It is a bit convoluted and counter intuitive. I'm holding off for a few days so that I can put together a better explanation. Hopefully someone will come along and do a better job than I could.I'll bite--why is that?
-TL
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No, it is not correct nor is it critical in a properly designed weapon. You must understand that much of the minutia in this is not fully understood by those who have dedicated years of study in science/engineering disciplines. Maybe you have special insight others do not possess.
The general consensus, just like wikipedia article you posted....
Is that in a properly designed rifle it has little effect but that is only an educated guess by those with engineering and science education in the field.
That means muzzle exit gases have no effect on a properly designed weapon.
So no, the natural color of a Sperm Whale is not white.
This is almost exactly the same thing as saying that they CAN have an effect. I don't understand how you can't see that.
They CAN have an effect on firearms with crown problems. This can be demonstrated in the real world. Which means that they must be a consideration when there are accuracy issues. The muzzle gases are moving very fast and have a lot of momentum upon exit--more than enough to cause bullet displacement/misalignment if they don't exit symmetrically due to a problem with the crown.
Yes, if the gun is set up right, you don't need to worry about muzzle gases. Just like when the gun is set up right and aimed right you don't need to worry about a lot of things that can affect the ability to hit the target as desired. But for the purposes of a discussion about the physics of shooting a rifle, it's important to understand that they are one of the factors that CAN have an effect since that's one of the avenues that must be explored if there are problems with the accuracy.
What you're doing at this point is like someone saying that "Bedding does affect rifle accuracy." and then you respond. "You're wrong. Bedding has no effect on rifle accuracy if the rifle is set up properly." Which is both incorrect and correct. The person is NOT wrong because bedding is a factor that affects rifle accuracy. But it is correct because bedding only affects rifle accuracy if there's a problem with the rifle that can be corrected with bedding. But more to the point, it's totally unhelpful.
It doesn't provide any useful insight at all because, in the current case, no one is arguing that muzzle gases always deflect bullets, even when things are working properly. Everyone already understands that if the muzzle is set up properly the gases aren't a problem.
So, if your point is that muzzle gases do not ALWAYS cause accuracy problems, then your point is duly noted. It should also be noted that: 1. No one ever made that claim. and 2. If someone says that muzzle gases do affect the bullet, that does not contradict your point since they can and do have the potential to affect the bullet and it's important to keep that in mind. and 3. Your original claim was that there was no way that they could affect the bullet, a contention which is obviously and demonstrably false.
Almost exactly like saying when the wings fall off an airplane it does not fly as well.
But is still an airplane without the proper wings it was supposed to have when it was deemed airworthy?
It is nothing like your stock bedding example.
We are talking about something that is fundamental to actual working order and design of the system.
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If someone claimed that the wing falling off an airplane does have an effect on its flight, and you initially claim that it can't happen, and then later modify your claim to say that wings don't fall off of airworthy airplanes, that would be a decent analog to the current exchange.
georgehwbush
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the whole passing gas argument seems stale now.
but let an uneducated idiot make an observation here.
to say that a gas can not exceed the speed of sound is like saying that the escaping "very high pressure" gas, has to stop at the muzzle and wait it's turn in line to exit now that the bullet is gone. look if the gases were traveling mach 3 when the cork popped; then like any other object, it requires space to slow down. and yes i know that the amount of resistance regulates how far, but you will be hard pressed to make a case that it is instant. laws of motion apply even to gases.
but let an uneducated idiot make an observation here.
to say that a gas can not exceed the speed of sound is like saying that the escaping "very high pressure" gas, has to stop at the muzzle and wait it's turn in line to exit now that the bullet is gone. look if the gases were traveling mach 3 when the cork popped; then like any other object, it requires space to slow down. and yes i know that the amount of resistance regulates how far, but you will be hard pressed to make a case that it is instant. laws of motion apply even to gases.
Concurred.
As Unclenick described in post #393, the bullet exiting the muzzle takes distance up to 11x caliber to catch up with the gas. For a .30 cal bullet, that's about 3". I wouldn't call Unclenick uneducated / uninformed.
I'm afraid we will have to wait a bit longer before we can move on to other topics. Patience young man!
-TL
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The nature of its movement changes and in order to influence the bullet it must overcome a normal shock. Your feeling the shock wave is not movement of the air as that dies very quickly and cannot pass thru the normal shock formed by the bullet nose upon contact with the atmosphere, it is vibration of the air once it reaches the muzzle exit. There is downstream flow that dies very quickly but it does not have the energy to exert any perceptible influence under normal circumstances.
To be very technical in any supersonic flow, there is a tiny portion that does exceed the speed of sound in some cases. It is very localized flow close to the body just before the normal shock depending on the shape of the body in flight. It get roughly mach 1.2 and represents air molecules being shoved out of the way by the shape traveling thru the air mass. They too slowdown and form a normal shock giving off energy as heat. All normal shock is air traveling at the local speed of sound.
It is not MY assertion that gas exit has no influence on a properly designed weapon to be perfectly clear. It is Sierra Engineers and I do agree with them because what they are saying fits with the physics of Aerodynamics as I was taught. I am in complete agreement with Sierra and US Army Engineers, NASA, and surprisingly...Wikipedia as written a few days ago, lol.
https://thefiringline.com/forums/showpost.php?p=6978558&postcount=404
https://thefiringline.com/forums/showpost.php?p=6962038&postcount=218
You see that line coming off the back of the bullet, that is a normal shock too. Any downstream disturbance would have to exert upstream influence and that is not how normal shock works.
https://www.grc.nasa.gov/www/k-12/airplane/machang.html
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I did think about it, and it is ludicrous. Devices clearly can be damaged and they can be manufactured incorrectly. That's why it’s important to understand what the effects can be when those things happen, as they inevitably will in some cases. Which is why it makes no sense for you to continue to attempt to discount the idea that crown issues are important because they don’t occur in properly set up rifles.
That’s a strawman. Nobody is saying that it’s normal for crowns to be damaged or improperly manufactured. The point is that the gases exiting the muzzle can affect the bullet so its important to make sure they exit the muzzle in a “well behaved” manner.
By the way, it’s important to recall that your initial position in this particular sub-discussion was that it is a physical impossibility for the muzzle gases to affect the bullet. That turned out to clearly be a false/incorrect/scientifically bankrupt claim and you still haven’t frankly admitted that fact. You are, in fact, still posting material in an attempt to support that position even though there's no question at all that it is incorrect. That information you keep posting and reposting does not, can not, in any way, shape or form, prove or even imply that the muzzle gases can not affect the bullet. That's how it is when one tries to disprove the truth. Anyone with a rifle can experiment with the crown and prove that muzzle gases can affect the bullet. You could prove it to yourself if you were willing to undertake the effort.
I will note again that you failed to address the contents of the paper I linked to that conclusively showed your assertion was wrong. You failed to address it because you didn't understand it. Which is not surprising given that you clearly don't fully understand the material you are posting--because if you did, you would not be trying to use it to support an obviously false claim.
Your fallback position, that muzzle gases don’t disturb the bullet significantly if the rifle is properly set up is a tautology (i.e. If the rifle is set up so the gases don’t affect the bullet then the gases don’t affect the bullet.) It is simply saying the same thing in two different ways. It is meaningless and pointless.
Gases can absolutely exceed the speed of sound in air by a significant amount, and not just at the edges of the gas jet. They won't continue traveling at that speed for very long in air because of the drag and momentum issues, but the entire flow can certainly travel at several times the speed of sound in air. I don't fully understand how you arrived at such an obviously false conclusion--I suspect you are basing it on an oversimplified or limited case but that you have failed to fully comprehend that simplification/limitation.
- What makes a bullet move down the bore? A supersonic jet of gas behind it.
- Which direction is the direction of flow? In the direction of bullet travel.
- Is the bullet, which is clearly upstream of the flow of gases influenced by the supersonic jet of gases behind it? Yes, of course it is, that is what moves it down the bore.
We know that bullets do move faster than the speed of sound and are pushed to that speed by a jet of gases moving faster than the speed of sound and therefore we also know from the simple questions and answers above that the statement you blindly quoted can't mean what you are claiming it means. If it did, it would be easily demonstrable to be contrary to reality. It would mean that guns can't shoot bullets faster than the speed of sound.
So let's think. Could it be that the example you pulled that quote from differs from the case under discussion? Could there, perhaps be a difference between the flow of gases caused by an object moving through air and pushing the air out of the way and a jet of gases that is traveling several times faster than the speed of sound in air?
Here are some more questions for you. If you will actually stop and think about these questions, and answer them correctly, or find correct answers to them, the process will help you tremendously.
1. What is rocket exhaust?
2. How fast can rocket exhaust travel on exit in air?
3. What are mach diamonds?
4. What is the difference between rocket exhaust and muzzle gases?
That's right, it's not. You actually claimed it couldn't have any influence at all under any circumstances, not just in the case of a properly designed weapon, and you are still posting material in an attempt to support that obviously incorrect claim.
This is beyond ridiculous. It’s clear to everyone you were wrong. It's time for you to admit it and move on. It happens—it’s no big deal. Being wrong is part of learning and learning is part of living. As someone once said, “When you stop learning you stop living in any vital and meaningful sense.” Your fallback position that if the bullet isn’t being significantly perturbed then the bullet isn’t being significantly perturbed is pointless in every possible meaning of the word. If you think it’s a telling point, that’s a much bigger error than your original claim that the exit of gases at the muzzle can’t affect the bullet. It's one thing to be confused about how muzzle gases work, it's another thing to get tangled up in an elementary logical fallacy. It is compounding your initial, understandable error with an additional error that’s even worse than the first one.
Look, I have 3 degrees in engineering/science/technology. I would never claim that because of that I can't be wrong. I wouldn't even claim that it makes me infallible in my own field of study. I've learned a lot since I got those degrees. I've learned that in some cases I didn't fully understand the material I thought I understood. I was able to do that because I was willing to accept reality. When presented with a situation where reality conflicts with something I thought I knew, I had to reassess what I thought I knew. You are currently in that dilemma. You think you know something, but it clearly conflicts with reality. You are choosing to ignore reality and that means you will persist in your error.
Factually, there are rules of normal behavior. Factually, there are exceptions to rules of normal behavior hence the term "abnormal".
That is not a strawman.
A flow that does not influence the upstream behavior past a normal shock.
A consequence of oblique shock formation and expansion wave formation not normal shock. You don't understand the difference in shock waves, characteristics of shock waves and shock wave formation. It has nothing to do with this conversation.
At no point does it cross a normal shock.
Nothing and neither will cross a normal shock. It is not called a barrier for nothing. If it was easy to cross, so many would not have died in the pursuit of getting past it and it would be a normal occurrence in nature.
This article appeared in UK Daily Mail and is NOT a scientific journal nor is the photography done in any controlled environment as per the author. It is simply high speed photography of a bullet being launched. It started out as a hobby and art with some bullet manufacturers being interested in the photos. I think it will enhance the conversation because of one very interesting photo.
Credit goes to
Article Title:
https://www.dailymail.co.uk/news/ar...ographer-captures-split-second-gun-fired.html
The photograph captures an image of the consequences of normal shock. This is normally hidden depending on the airflow around the weapon when it is shot and the temperature gradient.
The photo is captioned:
As an aid to the reader, I added a graphic depiction of the approximate normal shock formation.
It is interesting in that you can see some characteristics of normal shock. First is the flow just in front of the bow wave which is going to be very high pressure until at the very center is a what is called a stagnation point in which no flow occurs at all. That is the air that is moving at Mach 1 - Mach 1.2 just before Normal shock formation. You can see the area immediately after the normal shock which is extremely low energy to the point it is almost a vacuum. That is the characteristic of normal shock that killed pilots and test pilots. The rear of the bullet forms a normal shock upon exit as well.
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So what. No one is claiming that the case where the crown problems result in inaccuracy are normal. So it is a strawman.
I see you could not bring yourself to give actual answers to some of the questions. That's interesting because I've been assuming that you didn't understand the implications. It seems that you do understand them and therefore are reticent to give the correct answers because they will prove you wrong. I will answer them for you.
Rocket exhaust is a jet of gases that can travel much faster than the speed of sound in air. Rocket exhaust velocities can be thousands of m/s--far faster than the speed of sound in air. Your claim that gases can not move faster than the speed of sound in air is therefore false. Period.
Mach diamonds are the pattern of evenly spaced rings sometimes visible in the exhaust of an engine is sometimes referred to as shock diamonds or Mach disks. The phenomenon occurs anytime a flow exits a nozzle at supersonic speeds and at a pressure that is different than that of the external atmosphere. Mach diamonds are visible proof that gases can travel faster than the speed of sound in air--and that they can do so for a significant distance after they exit. Your claim that gases can not move faster than the speed of sound in air is therefore false. Period.
Oh, but it does, and the fact that you don't understand how it is relevant is extremely surprising.
Here's some more information about Mach diamonds: "The "diamonds" are actually a complex flow field made visible by abrupt changes in local density and pressure as the exhaust passes through a series of standing shock waves and expansion fans.
...
As the exhaust passes through the normal shock wave, its temperature increases, igniting excess fuel and causing the glow that makes the shock diamonds visible."
You are correct that rocket exhaust and muzzle gases are essentially the same thing. Which means that muzzle gases can travel much faster than the speed of sound, much faster than a typical bullet, as well, which means that they will interact with the bullet for some time after the bullet exits the muzzle, until drag dissipates the momentum of the gas jet. But we already knew that because when the gas exits the muzzle with significant asymmetry, as happens when there are crown problems, accuracy is affected.
The pictures and materials you provided are (big surprise) taken out of context because you do not fully understand the topic. They don't provide any useful information regarding the effect of the muzzle gases on the bullet or the velocity of the gases as they exit the muzzle.
You need to think about this question because if you can understand it and bring yourself to answer it honestly, it will provide you with a lot of insight.
Could it be that the examples you are quoting from and the laws you are stating are from situations very different from the case under discussion? Could there, perhaps be a difference between the flow of gases caused by a supersonic object moving through air and pushing the air out of the way and a jet of gases that is traveling several times faster than the speed of sound in air?
Because the answer is: "Yes, absolutely."
Wow,
You think that is saying the flow is supersonic and influencing anything upstream. That great temperature increase is the result of the flow forming a normal shock, slowing the air to almost still, and air becoming very low energy. What I said is correct.
The expansion waves and oblique shock form adding energy to increase the velocity of the flow. When the velocity increases enough, a normal shock forms and the process starts again.
Once again:
Rocket engines, jet engines, and mach diamonds have nothing to do with this conversation.
If you don't believe me....
Compare the mass flow of a Jet Engine to the Mass Flow of a 30.06 round....
Wrong. Mach diamonds can form in chains. What forms the next mach diamond in the stream if the exhaust is slowed to "almost still" after "passing through the normal shock wave" to create the first diamond?
You've been saying over and over that gas jets can't go past a normal shock. Now you are faced with incontrovertible evidence that your statement was incorrect.
"The "diamonds" are actually a complex flow field made visible by abrupt changes in local density and pressure as the <supersonic> exhaust passes through a series of standing shock waves and expansion fans.
...
As the exhaust passes through the normal shock wave, its temperature increases, igniting excess fuel and causing the glow that makes the shock diamonds visible."
...
As the exhaust passes through the normal shock wave, its temperature increases, igniting excess fuel and causing the glow that makes the shock diamonds visible."
It looks like it's going to have no effect whatsoever on your position. That's very disappointing.
You claimed that gases could not travel at supersonic speeds in air. That was obviously incorrect and there's ample proof. Then you claimed that supersonic gases couldn't pass through a normal shock. Now we have proof that was incorrect as well.
There's no escaping the reality that the gas velocity is traveling at supersonic velocities in air, that it passes through the normal shock, and that's it's supersonic both before and at points after passing through the normal shock wave.
You like posting diagrams and citing sources. Find one that indicates the velocity of all the gas after the first normal shock in a mach diamond series is subsonic.
Wrong again.
"When artillery pieces are fired, gas exits the cannon muzzle at supersonic speeds and produces a series of shock diamonds. " (This is a good one. It correctly states that gases exit the muzzle at supersonic speeds and notes that it can form mach diamonds. It contradicts two of your claims in one sentence.)
"One other interesting side note, shock diamonds aren’t just seen in rocket exhausts. They’ve also been seen blasting out of volcanoes and artillery guns."
"One other interesting side note, shock diamonds aren’t just seen in rocket exhausts. They’ve also been seen blasting out of volcanoes and artillery guns."
You've been saying things that can't be true. You've been making categorical statements that are proven wrong by real world observations. You've been making assertions that are contradicted by common knowledge. When you run up against proof that your assertions are incorrect, you never admit you're wrong, you merely try to shift the argument a little and make another (often incorrect) assertion.
Here's a quote you need to contemplate.
These are kinds of disciplines in the sciences that you have to learn. To know when you know and when you don’t know and what it is you know and what it is you don’t know. You’ve got to be very careful not to confuse yourself.
--Richard Feynman
--Richard Feynman
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