Physics of shooting a rifle

[JohnKSa]

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.

[davidsog]

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.

LOL.

Think about what you just wrote and ponder why anyone would argue that devices cannot be damaged?
Why would a principle of normal behavior be built around the fact a failure has to occur in order for the principle to be true?

[georgehwbush]

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.

[tangolima]

Originally Posted by georgehwbush

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.

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

Sent from my SM-N960U using Tapatalk

[davidsog]

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.

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.

Throughout the trajectory, including the initial transient period, the bullet has an “average” angular orientation which aligns the longitudinal axis almost exactly with Vbullet relative to the air.

https://thefiringline.com/forums/sho...&postcount=404

https://thefiringline.com/forums/sho...&postcount=218

There is no upstream influence in a supersonic flow;

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

[JohnKSa]

Think about what you just wrote and ponder why anyone would argue that devices cannot be damaged?

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.

Why would a principle of normal behavior be built around the fact a failure has to occur in order for the principle to be true?

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.

To be very technical in any supersonic flow, there is a tiny portion that does exceed the speed of sound in some cases.

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.

There is no upstream influence in a supersonic flow;

• 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?

It is not MY assertion that gas exit has no influence on a properly designed weapon to be perfectly clear.

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.

[davidsog]

That’s a strawman.

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.

What is rocket exhaust?

A flow that does not influence the upstream behavior past a normal shock.

What are mach diamonds?

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.

How fast can rocket exhaust travel on exit in air?

At no point does it cross a normal shock.

. What is the difference between rocket exhaust and muzzle gases?

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

By Chris Pleasance

Published: 13:53 EDT, 29 December 2013 | Updated: 13:53 EDT, 29 December 2013

Article Title:

Faster than a speeding bullet: Photographer captures split second after gun is fired

https://www.dailymail.co.uk/news/art...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:

Slow motion: This image shows a pressure 'shell' forming around the bullet as it tears out of the barrel

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.

[JohnKSa]

Factually, there are rules of normal behavior. Factually, there are exceptions to rules of normal behavior hence the term "abnormal".

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.

It <Mach diamonds> has nothing to do with this conversation.

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."

[davidsog]

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."

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.

A flow that does not influence the upstream behavior past a normal shock.

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:

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.

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....

[JohnKSa]

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.

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."

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.

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.

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.

Rocket engines, jet engines, and mach diamonds have nothing to do with this conversation.

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."

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

[georgehwbush]

david (https://thefiringline.com/forums/att...1&d=1723906688)

i like the photo you posted, it shows gases influence farther away from the muzzle than the bullet, thus proving that supersonic flow of gases from the muzzle is possible. nice move. <check/>

not only are they further than the bullet, but they had to change dirrection to get there. those little atoms are in a hurry !

one other thing, i didn't notice anyone mention the compressed air in front of the bullet which exited ahead of the bullet, at supersonic speed of course! which will have an affect on the bullet when it has to pass through that MESS.

[davidsog]

Mass Flow, John....

You think I claim air does travel at supersonic speeds. I never said that. I said normal shock does not flow any faster than the speed of sound.

Once again, you do not understand shock wave formation or the characteristics of shock waves.

As for your big revelation of mach diamonds forming a chain....

What do you think "and the process starts again".

Nowhere in a mach diamond does flow cross a normal shock at supersonic speeds or at any speed other than extremely low energy separated flow.. Nowhere, John....

[davidsog]

I will try and explain characteristics of shock waves for you. That might help out. Give me a few days as I am at work putting these concepts in action, ������

[JohnKSa]

Originally Posted by davidsog

You think I claim air does travel at supersonic speeds. I never said that.

Originally Posted by davidsog

Exhaust gases exiting the muzzle cannot travel faster than the speed of sound and they almost instantaneously adhere to that once they exit a confined space.

Originally Posted by davidsog

There is no a 5000fps movement of gas once it escapes the muzzle.

Instead, the motion becomes a vibrational wave which is the basis of normal shock. That vibration is speed limited by the speed of sound.

Originally Posted by davidsog

The gas at exit can only travel at the speed of sound at the local flow level. The bullet is traveling much faster than that.

Originally Posted by davidsog

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.

For the third time on this thread. What sort of game are you playing? Why would you say one thing multiple times and then try to pretend that you didn't?

I will try and explain characteristics of shock waves for you.

No.

FIRST, you explain why you have repeatedly claimed that muzzle gases can't travel faster than the speed of sound in air and/or faster than the bullet when clearly they do.

I provided a technical source that proves they do (1900m/s) and explicitly states that they catch and impact the bullet and you completely ignored it. As in totally failed to acknowledge its existence.

Hatcher measured them traveling several times the speed of sound in air--4700fps. You have completely ignored this fact.

Muzzle crown issues that don't touch the bullet and still cause accuracy issues prove that they do. You tried to discount this saying it wasn't a normal case--which is true--but not relevant since it proves that the gases do affect the bullet in spite of the fact that you say they can't catch the bullet and in spite of the normal shock which you claim prevents that.

IF you have changed your mind about muzzle gases being able to travel faster than the speed of sound in air:

1. Please have the common courtesy and decency to explicitly state that fact in clear English rather than trying to pretend that you never made the claim in the first place. It would be nice if you could explain where the confusion arose that caused you to make multiple contrary-to-fact assertions.

2. You posted charts and pictures and sources to support your assertion. If you have any integrity (personal, professional, technical), and your goal is to share knowledge and inform, you will want to explain how and why you took those plots out of context, and/or misunderstood/misinterpreted them so others will not make the same mistakes.

3. Stop arguing the point. Once a point is settled, there's no need to keep arguing as if it's not settled.

Then we can move on to the next topic. There's no point in having multiple balls in the air at once.

[Unclenick]

Think of the propellant gas molecules as little bullets at a higher temperature (higher average kinetic energy) than the surrounding air. This is what enables them to exceed the speed of sound as they blow out of the muzzle and into the outside air. As soon as interaction with that air has depleted enough of their kinetic energy, they drop to the same temperature as the outside air. This takes a little travel distance and time. The shockwave they create propagates outward, and after the first couple of feet, it is going no faster than the speed of sound in outside air. It might make an interesting analog to the rapid expansion period after the Big Bang.

[davidsog]

There is no guesswork as to the speed of the air in a normal shock.

I will be back on to try and help you all to understand what is going on.

It is a physical property of the normal shock that the velocity of the air is fixed. There is only one tiny tiny portion that exceeds the ambient speed of sound and it no faster than Mach 1.2 at its greatest speed. The velocity of the air reaching the ambient speed of sound IS the Normal Shock. Immediately behind the Normal shock, the velocity of the air is zero. From there it picks up speed but it does not become supersonic or faster than supersonic without oblique and expansion shock.

Those two shock waves add velocity that can exceed the ambient speed of sound but wherever a normal shock is seen.....
The air is moving no faster than the ambient speed of sound.

That is how the physics works.



No amount of speculation, conjecture, or posturing will change the physical properties of Shock Waves.

Normal Shock is ALWAYS MACH 1 and the air behind it subsonic. There is no physical possibility for anything to influence anything UPSTREAM of a normal shock.

[davidsog]

FIRST, you explain why you have repeatedly claimed that muzzle gases can't travel faster than the speed of sound

I never said gases cannot travel faster than the speed of sound. I said they do not travel faster than the speed of sound in a Normal Shock and in the atmosphere they do not do so for any distance without lots of mass flow. A gunshot does not have the mass flow to be able create a supersonic stream of air for any distance. It does impart a very energetic vibration like all explosions do....

Stop taking my original statement out of context from the discussion of a bullet exiting the muzzle of a gun......


You understand that the air is not moving around the bullet but rather the bullet is moving thru the air. If it was not for the bullet being there...
There might be a tiny portion of supersonic air exiting the muzzle. As it stands, the Normal Shock of the bullet prevents any significant disturbance coming from anything DOWNSTREAM of the bullet to enact UPSTREAM influence over a Normal Shock.

The properties of Normal Shock are immutable laws of physics. Not understanding that does not change it.


Those thick lines at the front and the rear of the bullet ARE Normal Shock:



You can also see the "Pressure Shell" as the author of the high speed photo article called it formed by the bullet as it encounters the atmosphere. That is a very accruate description despite its not being very technical.

[JohnKSa]

Originally Posted by davidsog

I never said gases cannot travel faster than the speed of sound.

You absolutely claimed several times that the muzzle gases could not travel faster than the speed of sound. You also stated that they were going much slower than the bullet.

I will provide these quotes again.

Originally Posted by davidsog

Exhaust gases exiting the muzzle cannot travel faster than the speed of sound and they almost instantaneously adhere to that once they exit a confined space.

Note that you absolutely did say they can't travel faster than the speed of sound.

Originally Posted by davidsog

There is no a 5000fps movement of gas once it escapes the muzzle.

Instead, the motion becomes a vibrational wave which is the basis of normal shock. That vibration is speed limited by the speed of sound.

Note that you did say that the muzzle gas movement was limited to the speed of sound in air. But it clearly is not.

Originally Posted by davidsog

The gas at exit can only travel at the speed of sound at the local flow level. The bullet is traveling much faster than that.

Note that you claimed the bullet was traveling much faster than the muzzle gases but, in fact, the gases are traveling much faster than the bullet when they exit the muzzle and, as the source I provided proves, they do catch the bullet.

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.

Note that you did state that only a tiny portion of the gases could travel fater than the speed of sound which is not true. The muzzle gases exiting the muzzle are initially traveling several times the speed of sound in air (not "roughly mach 1.2) and stay supersonic for a non-negligible distance.

In fact, you are still making the claim. I have to say, this is pretty remarkable--you are claiming you didn't say something that you clearly did say and at the same time re-iterating the point and arguing in support of it. Quite a novel debate technique.

Originally Posted by davidsog

There might be a tiny portion of supersonic air exiting the muzzle.

Wrong. The muzzle gases exit at several times the speed of sound in air and stay supersonic for a non-negligible distance.

You understand that the air is not moving around the bullet but rather the bullet is moving thru the air. If it was not for the bullet being there...

You are trying to change the subject. This is about the muzzle gases and very clear and specific claims you have made about their speed on exit and their behavior after exit.

That is how the physics works.

If you believe that physics prevents the muzzle gases from exiting at several times the speed of sound and from traveling at supersonic speeds for a non-negligible distance, then you don't understand the physics because physics does not provide information that is contradictory to real-world observations. That is, in fact, the foundation of science--it must be consistent with real-world observation.

There's no point in continuing until that issue has been resolved.

If you have changed your position and are now agreeing that the muzzle gases can travel faster than the speed of sound in air, much faster, in fact, than the bullet, and can catch and affect the bullet as the source I provided proves, then please clearly say so and stop arguing the point. Also, if you really are motivated by a desire to provide knowledge and understanding, you will certainly want to explain what it was that led you to make such an elementary error and how you misinterpreted the plethora of supporting data you provided to support the incorrect claim.

[davidsog]

You absolutely claimed several times that the muzzle gases could not travel faster than the speed of sound.

John, in many ways we have much in common in this discussion. I had very good professors and attended one of the top 5 engineering schools for this discipline. Fortunately, those professors were able to explain this barney level to a glorified grunt.

It might help for you to understand how supersonic air enters and exits a tube.

Again, this will also highlight the importance of a good properly formed crown in a barrel.



That normal shock is of course reversed as our flow of our expanding gases exit the barrel. That is not important. What is important is the fact that normal shock is right at the exit and completely covers the exit of the barrel. That normal shock would exist with and without a bullet in the way and it just formed by the nature of the gas movement encountering the air mass(atmosphere).

In an jet engine we have what is called a variable exhaust nozzle. Think of it like a crown of a barrel that can change shape including to an improperly formed crown. That is how your get your mach diamonds you were focusing on but please forget those...it won't help you understand what is going with a bullet because our barrels have proper crowns without variable exhaust nozzles. This property is also why supersonic aircraft can have air breathing turbine engines.

The shape of the crown forms expansion waves conserving energy as the flow can provide it. Those expansion waves will not cross a normal shock to influence anything upstream. Those expansion waves at the crown will increase the velocity of the airflow until the run out of energy and without mass flow that takes very little time. When the bullet exits, it is forming its own Normal Shock. It forms a normal shock immediate upon contact with the air mass both at the bow and at the rear of the bullet when it reaches the air mass.

That Normal Shock formation at the muzzle exit send that energy out as a vibration that creates that ball of normal shock expanding at the muzzle.



Two questions you must have the correct answer too in order to understand what is going on.

1. What is the velocity of the air at the normal shock?

2. What is the velocity of the air immediately downstream of and behind the Normal Shock?

[JohnKSa]

So, are we back to you saying that they can't exit at supersonic speeds again? Just trying to keep things straight.

Fortunately, those professors were able to explain this barney level to a glorified grunt.

I would argue that they, in fact, did not, given that your understanding of the situation obviously contradicts real world observations. Muzzle gases do exit at substantially higher than the speed of sound in air and continue at supersonic speeds for some non-negligible distance after exit.

What I think is going on is that you understand a specific case very well and assume that it is more universal than it is. So you are taking correct principles from one case to another case where they do not apply--which is resulting in nonsensical claims and assertions.

I provided a source that proves how muzzle gases behave and you have studiously ignored it since I posted the link.

https://www.mdpi.com/2226-4310/11/5/...20its%20bottom

...the high-temperature and high-pressure gas jet expanded at a much higher rate than the velocity of the moving body. It expanded more quickly under the influence of the initial jet. The muzzle jet encountered the moving body...

"The high-temperature and high-pressure gas was sprayed behind the moving body, rapidly expanded at a speed above 1900 m/s, and chased and impacted the body to form shock waves at its bottom and on both sides of it."

[davidsog]

I provided a source that proves how muzzle gases behave and you have studiously ignored it since I posted the link.

There is nothing in that report that refutes a single thing I have said nor is there anything that says muzzle gases have any effect on a bullet.

It actually relates what I just told you in my last post.

The muzzle jet continuously sprayed out gas, and the forward-moving shock wave collided with the reflected shock wave to suppress its development.

The shock wave of the muzzle jet under interference by the initial jet was complex and featured shock–shock collisions and shock–vortex collisions in the flow field that suppressed the expansion of the muzzle jet and led to the formation of multiple reflected shock waves and high-pressure zones.

You can clearly see that in the photos.

In fact, it concludes exactly what I said in my first post on this subject:

Owing to the low energy of the initial jet—one order of magnitude lower than the energy of the muzzle jet—the force of its impact on the high-speed moving body was relatively small, while the impact on its lifting force was relatively large but could be ignored.

You understand that the largest component of energy delivered to the bullet CAN BE IGNORED......

It is not enough energy to overcome the bullets energy to cause a positional shift..........

Not surprising at all given that it must cross a normal shock.....which is a violation of the laws of nature.

davidsog says:

Knowing what I know of Aerodynamics as a someone formally educated in Aeronautical Sciences my first instinct is that the gases escaping from the barrel do not influence the flight significantly in MOST cases provided everything is in proper working order for the rifle and ammunition.

https://thefiringline.com/forums/sho...&postcount=398

I am banging my head against a wall here and making my pistol rusty from sticking it my mouth.

If you correctly answer those questions at the bottom of my last post, you will go a long way towards figuring this out for yourself.

[davidsog]

The muzzle jet encountered the moving body...

The rest of that sentence is important:

The muzzle jet encountered the moving body such that this suppressed its development and led to a reflection in the shock wave and a change in its direction of propagation.

There is a shock wave collision between the Normal Shock of the bullet and the Normals Shock formed by the gas exiting the tube.

That collsion changes the direction of the shock wave propagation. It does not change the direction or flight of bullet.


Understand??? The shock collision suppresses the exiting muzzle jet.

[JohnKSa]

There is nothing in that report that refutes a single thing I have said...

That's obviously not true.

You've said that the gases are moving slower than the bullet after exit. The report absolutely contradicts that.

You've said that the gases are not exceeding the speed of sound in air. The report absolutely contradicts that.

I am banging my head against a wall here and making my pistol rusty from sticking it my mouth.

I can see that it must be extremely frustrating for you. It is obvious that you have made claims that are incorrect and unsupportable and yet you can not seem to bring yourself to admit it, even in the face of absolute proof that you are wrong.

So, are you still claiming that the muzzle gases are subsonic and that the bullet is moving much faster?

[davidsog]

You've said that the gases are moving slower than the bullet after exit.

John

What is the velocity of the air immediately downstream of and behind the Normal Shock?



The answer is in the Middle column there, under Normal Shock.

Cross reference it with "Effect of Velocity and Mach Number"

I highlighted it for you so it would be easier to find.

It says something about SUBSONIC. Is your bullet traveling at a subsonic speed?

[JohnKSa]

This is really, REALLY simple. Are you saying that these two statements from the paper are wrong?

"...the high-temperature and high-pressure gas jet expanded at a much higher rate than the velocity of the moving body..."

"The high-temperature and high-pressure gas was sprayed behind the moving body, rapidly expanded at a speed above 1900 m/s, and chased and impacted the body to form shock waves at its bottom and on both sides of it."

Unless these two statements are both wrong, your statements about the velocity of the muzzle gases can not be correct.