Physics of shooting a rifle

[davidsog]

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

Yes. Just like your report says it does....

[davidsog]

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

John,

Expansion waves will increase the velocity and increase the velocity to supersonic. Expansion waves are not normal shock wave. Very different animals. So when I said multiple post's back that expansion waves form....
It means the velocity increases.

You are very much misunderstanding and confusing when the report is talking about airflow behavior of the muzzle jet that has NOTHING to do with effects on the bullet.

Different subjects.

The FACT Normal Shock forms at the front and rear of the bullet isolates the bullet.

The FACT normal shock forms at the muzzle due the exit gases encountering the atmosphere means the air is subsonic at the muzzle.

Expansion waves will form on the crown and the report is saying the collision of those normal shocks changes the direction of propagation of the wave. There is not enough energy from the exit gases to effect the bullet.

That is what your report says.....

[JohnKSa]

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

I understand that you didn't read that report very carefully.

"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."

"The moving body accelerates and compresses the air in front of it under the propulsion of gunpowder gas in the tube to form the initial jet."

The initial jet is the gas in front of the bullet, which is quite different from the gas jet/muzzle jet that follows the bullet out of the muzzle.

Just like your report says it does....

Well, it's clear that this is pointless. When the paper very obviously and repeatedly says X and you claim it doesn't that sort of limits the possibility of constructive exchange.

Is it that you don't believe that 1900m/s is faster than the speed of sound? It is. It's over 5x the speed of sound.

Or is it that you do not understand what "chased and impacted" means? That can't happen if, as you claim "the bullet is traveling much faster than" the gas jet.

[davidsog]

The initial jet is the gas in front of the bullet, which is quite different from the gas jet/muzzle jet that follows the bullet out of the muzzle.

The point is the shock wave collisions John.

And what is the speed of the Normal Shock formed at the bow of the bullet in the initial jet....

What is the speed of the Normal Shock formed at the muzzle?

What is the speed of the Normal Shock formed at the end of the bullet



Mmmmmmm

5. Conclusions
In this study, we examined the characteristics of development of shock waves and vortices in a muzzle jet in case of interference by the initial jet for a launch device with a large diameter and a long barrel with a high kinetic energy of the muzzle. The conclusions are as follows:
(1)
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.[B] The strong shock wave of the muzzle jet collided with the weak vortex of the initial jet, causing it to disappear and leading to the formation of a stable vortex of the muzzle jet in the flow field. The muzzle jet without interference by the initial jet had a clear and simple structure.

Well, conclusion number one says NOTHING about the bullet. It speaks only of the flow field.

Is it that you don't believe that 1900m/s is faster than the speed of sound? It is. It's over 5x the speed of sound.

Or is it that you do not understand what "chased and impacted" means? That can't happen if, as you claim "the bullet is traveling much faster than" the gas jet.

You are confusing case 2, a simplified model to clarify the flow field....with reality.

Figure 14 shows changes in the pressure (0.5 ms~10.0 ms) in Case 2 (the model without interference by the initial jet) on the plane of symmetry over time. Due to the absence of interference by the initial jet, the structure of the muzzle jet was more regular than that in Case 1. The body moved forward at a high speed to form a CS at the front. 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.

Case 1 involved the complete structure shown in Figure 1a. It featured a moving body, a 30 m long tube, and the domain around the muzzle. Case 2 ignored the motion of the body inside the tube, as shown in Figure 1b, and considered only its motion outside the muzzle. Case 3 ignored the moving body altogether, as shown in Figure 1c, and involved only the initial jet and the muzzle jet. In Case 4, the motion of the body inside and outside the bore was ignored, as shown in Figure 1d, and only the domain outside the muzzle was considered.

The report is very clear on its conclusions. If your conclusions are different, then they are probably not correct, John.

[JohnKSa]

You are confusing case 2, a simplified model to clarify the flow field....with reality.

You still haven't read the report. It contains data collected from an actual firing. Figure ten shows: "Development of the supersonic muzzle jet over time."

Also from that section:

"...the velocity of the gas ejected from the muzzle exceeded that of the moving body..."

" the high-temperature and high-pressure gunpowder gas inside the tube was quickly sprayed out to chase and surround the moving body."

"Therefore, the method of simulation used in this paper could accurately simulate the characteristics of the muzzle jet of the models."

Well, isn't that interesting. The real world experiment showed that the gas jet moves faster than the bullet. It chases and surrounds the bullet. And it showed that their models were accurate.

Well, conclusion number one says NOTHING about the bullet.

Just out of curiosity, did you even bother read the first sentence of the Introduction? You know, the reason that the research was done in the first place?

I'll quote it now, just for fun.

"When a barrel weapon launches a projectile, the muzzle flow field will cause initial disturbance to the projectile’s flight, reducing its shooting accuracy and increasing its impact point dispersion."

The report is very clear...

Indeed it is.

The point is the shock wave collisions John.

Actually, the specific point is the quote you took from the report does not say what you claimed it does. You didn't read (or didn't understand) that the initial jet is not the gas jet/muzzle jet. The gas jet/muzzle jet is an order of magnitude more energetic than the initial jet.

The more general point is that you are mining the report for things that you believe support your point of view and both making errors in that determination based on carelessness or lack of understanding and apparently ignoring anything that contradicts you, however clear that contradiction is. Another example of a rather disturbing pattern of behavior.

Worse yet, even when faced with the incontrovertible truth that you screwed up (i.e. confusing the initial jet with the muzzle jet/gas jet and using that as the basis to try to make a point) you still can't bring yourself to admit that you made an error.

This all highlights the total uselessness of this exchange.

• You post things and then feel free to contradict them later, even when faced with your original posts.
• You post supporting material and then contradict it, presumably because you don't understand it.
• You accept sources as valid but then blatantly contradict the contents.
• You quote material from sources that you accept as valid but then make it clear by your comments about the material that you didn't understand it.
• It appears that you are unable to admit it when you make an error.

The combination of all those, especially the last point, means that it's impossible to have a constructive exchange and pointless to try. And I think I've had enough pointless to last me for awhile.

[davidsog]

When a barrel weapon launches a projectile, the muzzle flow field will cause initial disturbance to the projectile’s flight, reducing its shooting accuracy and increasing its impact point dispersion."

No, that is your morphing what they are looking for into your own desires.

This is exactly what they were investigating.

Large-caliber and long-barrel weapons are important experimental devices for exploring the impact resistance and reliability of warheads. The force of impact of the muzzle jet has a significant influence on the overload resistance of the warhead and surrounding devices. The mechanism of motion of the body inside the tube cannot be ignored owing to the high kinetic energy at the muzzle.

For some reason, you seem to have drawn a conclusion in absence of the any investigation. They did the investigation and came to a very different conclusion from you.

It contains data collected from an actual firing.

And? That has nothing to do with the fact they built a mathematical model to simulate that firing and you are confusing a simplified model to clarify the flow field.....with reality.

You are using the example that they removed the effects of the initial jet.

What it does your report conclude about using the simplified model without the effects of the initial jet:

If the distance to the muzzle is not considered under the operating conditions considered here, the muzzle jet without the initial jet-induced interference can be used as a simplified model for calculation beyond a distance of 5 m. [/B]

Under specific parameters, the simplified model you are quoting only works at distances away from the muzzle....

Anything other than that the simplified calculations can be used only IF:

When considering a location close to the muzzle and ignoring the moving body, the muzzle jet under interference by the initial jet can be used as a simplified model for calculation.

IF you ignore the fact the bullet is making Normal Shock Waves....

Shock Waves which lead too:

The strong shock wave of the muzzle jet collided with the weak vortex of the initial jet, causing it to disappear and leading to the formation of a stable vortex of the muzzle jet in the flow field.

Please stop avoiding it and answer the questions I have asked.

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?

Your "ah-Ha, Gotcha Report" is useful for designing a crown or a muzzle brake for an artillery piece but it does not make the claims you think it does....

The report seeks to devise a mathematical model for the flow of the muzzle jet. However the report says little to nothing about the effects of that muzzle jet on the flight of a bullet and actually provides evidence that it The Sierra Engineers were correct.

End this debate, John....
Simply point out the math in your report that illustrates the behavior of the bullet when the muzzle jet strikes it.

[davidsog]

is all highlights the total uselessness of this exchange.
You post things and then feel free to contradict them later, even when faced with your original posts.
You post supporting material and then contradict it, presumably because you don't understand it.
You accept sources as valid but then blatantly contradict the contents.
You quote material from sources that you accept as valid but then make it clear by your comments about the material that you didn't understand it.
It appears that you are unable to admit it when you make an error.

Just answer two simple question and stop making personal attacks please. Your perception of what is going on is wrong. Again, answer these two simple question....

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?

Answer these and we can talk about what a stable vortex is and you can tell me how that will effect our bullet upstream of a normal shock.....

[JohnKSa]

Just answer two simple question and stop making personal attacks please.

No personal attacks, just simple statements of fact based on your behavior. And no, I'm not going to entertain any attempts to distract from your incorrect assertions about the muzzle jet velocity and its ability to catch the bullet. There's no point in moving on until that point is resolved.

No, that is your morphing what they are looking for into your own desires.

That's a ridiculous assertion. What I posted was a direct quote from the report. You clearly see only what you want to see. Here's a case in point. You apparently missed this bit of information when you made one of your quotes.

"The force of impact of the muzzle jet has a significant influence on the overload resistance of the warhead and surrounding devices."

The muzzle jet is the gases that exit the muzzle behind the bullet. You claim it can't catch the bullet and that it's moving slower than the bullet. In fact, the very statement you quoted states that it can and does catch and impact it and has a significant influence on it.

Your "ah-Ha, Gotcha Report"...

What it does your report conclude about using the simplified model without the effects of the initial jet:

First of all, it's not my report by any stretch. Trying to couch it in that manner is silly and obviously desperate.

Second, if you object to the use of the material from models (although the report said they were accurate) then ignore them and look ONLY at the results from the actual firing.

"...the velocity of the gas ejected from the muzzle exceeded that of the moving body..."

" the high-temperature and high-pressure gunpowder gas inside the tube was quickly sprayed out to chase and surround the moving body."

You are smart enough to realize that those two statements of fact from observations of the real-world firing are sufficient to absolutely disprove your assertions about the muzzle jet.

It's absolutely clear that you are wrong and even more clear that you will never admit it. Pointless.

[davidsog]

And no, I'm not going to entertain any attempts to distract from your incorrect assertions about the muzzle jet velocity and its ability to catch the bullet.

Well John, I won't be able to help you then.

Show us all where in your report it describes the effects on a moving bullet and show us the math to quantify those effects.

You cannot because the report does not say that. The report says that when the expansion waves caused by the muzzle jet after they have formed a normal shock exiting the tube like any other flow collide with the Normal Shock created by initial jet and form a stable vortex.

Explain how a stable vortex imparts asymmetrical loads on a flying bullet upstream of the normal shock formed by the bullet.

Simply put, it does not effects it at all.

End this debate, John....
Simply point out the math in your report that illustrates the behavior of the bullet when the muzzle jet strikes it.

[davidsog]

"The force of impact of the muzzle jet has a significant influence on the overload resistance of the warhead and surrounding devices."

What is overload resistance, John? How does it affect explosives?

Answer those two questions and reevaluate your thoughts on this sentence....

[davidsog]

Figure 13. Changes in the pressure of the muzzle jet over time in Case 1.

[JohnKSa]

Show us all where in your report it describes the effects on a moving bullet and show us the math to quantify those effects.

The fact that the report proves two of your claims wrong doesn't make it my report.

Simply point out the math in your report that illustrates the behavior of the bullet when the muzzle jet strikes it.

Do you realize how puerile it is to try to discount the contents of the report by characterizing it as somehow being mine? The report is just the report. You were fine with the report until you realized that it directly contradicted your claims. Then, suddenly, it became my report.

Ok, that aside, this is just an attempt to distract from actual point. You claimed that the gases were moving slower than the bullet. That is clearly not true and the report proves it. Both the modeling and the real-world observations demonstrate that your claim was incorrect. You want to make it seem complicated but it's simple. You said the muzzle velocity was going slower than the bullet, but clearly it is not. There's no math required to see that you have claimed one thing and the report clearly states the opposite.

What is overload resistance, John? How does it affect explosives?

Another (remarkably feeble) attempt at distraction. If the muzzle jet is going slower than the bullet, as you claim, it can't impact it at all, and yet the direct quote from the report clearly states that it does impact it and that the "force of the impact" has a measurable effect on it.

Oh the diagrams you captioned are fun.

In the first one, you noticed, of course, that the vortices you highlighted are out in front of the projectile. How does that happen with the muzzle jet moving slower than the bullet?

Your sarcastic caption to the last one is laughable. By the time that frame takes place, 10ms, the bullet has moved 20 feet or more downrange. Did you think that anyone here was claiming that the muzzle jet was still affecting the bullet at that point? I haven't seen anyone making any claims like that. By the second figure in the series, the bullet is already a couple of feet from the muzzle. What was being discussed here happens before that point.

Do you really believe that your transparent attempts to distract from the point are going to be effective? Unless you can modify the report contents, you're not going to be able to wiggle out of this. And pretending that I'm the one who can end the debate is nonsense. Well, maybe not. I guess I could end it by agreeing to something I know is untrue. Is that what you want? Is it so important for you to feel like you "won" that you would encourage someone to agree to an untruth so you could achieve that goal?

[davidsog]

John,

Case 2 examines the effects of the muzzle blast in isolation. There is no effects of bullet or the initial jet modeled in Case 2

You are taking the explanation of what is going on in Case 2 and applying that to the real world. Case 2 is not reality. It is just a tool to help understand everything that is going on.



The report models the initial Jet isolation as well. It is not reality but just one small part of what is going on. Seeing it in isolation helps to understand what is going on with the big picture just like modeling the Muzzle Jet in isolation does....

[JohnKSa]

There is no effects of bullet or the initial jet modeled in Case 2

I'll give you the benefit of the doubt and assume that you just made an error here. Case 2 does include the motion of the projectile outside the muzzle.

"Case 2 ignored the motion of the body inside the tube, as shown in Figure 1b, and considered only its motion outside the muzzle."

You are taking the explanation of what is going on in Case 2 and applying that to the real world. Case 2 is not reality.

Sorry, that's a lie. The real-world observations from the report (no modeling involved) demonstrate that the muzzle jet is moving faster than the bullet on exit and therefore disprove your claim.

I pointed this out yesterday (since you apparently missed it when you read the report) and you have studiously ignored that fact in all of your responses since then.

[davidsog]

Quit focusing on me and focus on the information the report is giving you.

It would help if you bothered to learn the physical laws that govern shock wave formation too.

It would keep you from concocting conspiracy theory while we discuss a very complicated situation that even the best engineers are not sure of exactly what is going on. You can bet that none of those engineers thinks the laws of physics are being changed or violated.

[davidsog]

Sorry, that's a lie.

Figure 14 shows changes in the pressure (0.5 ms~10.0 ms) in Case 2 (the model without interference by the initial jet) on the plane of symmetry over time. Due to the absence of interference by the initial jet, the structure of the muzzle jet was more regular than that in Case 1. The body moved forward at a high speed to form a CS at the front. 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. The moving body gradually freed itself from the impact of the muzzle jet and flew forward at a high speed. At this point, a complete muzzle jet was formed containing a CS, BoS, MD, bottom shock waves of the moving body, and an SS.

Figure 14. Changes in the pressure of the muzzle jet over time in Case 2.

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

[JohnKSa]

It was too much trouble to quote the second sentence in that two sentence paragraph?

Sorry, that's a lie. The real-world observations from the report (no modeling involved) demonstrate that the muzzle jet is moving faster than the bullet on exit and therefore disprove your claim.

I see you are still unwilling to address the real-world observations from the report.

It would help if you bothered to learn the physical laws that govern shock wave formation too.

You know what would really help? For you to stop playing foolish games and dodging around the truth in an attempt to "win". How about instead of trying to "win" you focus on the truth and on informing people, on sharing knowledge.

The report states in no uncertain terms that the real world observations indicate that the muzzle jet travels faster than the bullet. You made a statement that DIRECTLY contradicts that statement of fact. That's the actual sticking point here. Don't pretend like this is somehow my fault. I'm just the poor schmuck who noticed that what you said wasn't true and was willing to point it out.

[davidsog]

The real-world observations from the report

The real world observations say nothing about anything impacting the flight of the bullet.

The real world observations relate that it was simply too difficult to determine anything conclusive.

The high-speed camera recorded the dynamic characteristics of the launch device, and obtained the development and structural characteristics of the supersonic muzzle jet. Owing to the large amount of charge required to launch the body and its high kinetic energy, the gunpowder burned negatively in the chamber and underwent secondary combustion after being ejected from the muzzle. The resulting muzzle flame made it difficult to determine the shape of the shock wave. As shown in Figure 10a, the moving body traveled at a high speed inside the tube, pushing the air in front of it to form compression waves. These compression waves continuously propagated toward the muzzle but did not spread to it. Figure 10b,c show that the air in the front of the moving body was squeezed out of the muzzle to form the initial jet. The sprayed gas rapidly expanded, resulting in a decrease in pressure and an increase in velocity, and diffused into the environment. The wave front of the initial jet was approximately spherical, with a weak impact force that was one order of magnitude smaller than that of the subsequent gunpowder-induced gas jet. At this point, a small amount of gas leaked from the gap between the moving body and the tube to form a small area of the flame at the muzzle.

Figure 10. Development of the supersonic muzzle jet over time.

Figure 10d shows that, when the moving body left the tube, the high-temperature and high-pressure gunpowder gas inside the tube was quickly sprayed out to chase and surround the moving body. The flow field of the gunpowder gas had a spherical structure. A large amount of gunpowder and gas was sprayed out of the muzzle, causing secondary combustion and forming a large area of high-temperature turbulent combustion. As the projectile moved, the muzzle jet could not surround it, and they gradually separated. A unique shear layer was formed on the side of the moving body, starting at its head and then extending outward from its side. Because the velocity of the gas ejected from the muzzle exceeded that of the moving body, a clear shock wave was formed at its bottom.

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

They tell you John that it is not representative as it not normal to have extreme amounts of secondary propellant combustion. It does not negate what they are doing in building their mathematical model.

They flat out tell you:

Owing to the large amount of charge required to launch the body and its high kinetic energy, the gunpowder burned negatively in the chamber and underwent secondary combustion after being ejected from the muzzle.

That the nature of their test apparatus makes it impossible to not have extreme amounts of secondary combustion. That does not mean it is applicable to your properly designed rifle firing properly designed ammunition. They are not trying to do that. They are building a model and for that purpose, the apparatus is just fine.

That report constructs a SIMPLIFIED method of predicting initial and muzzle jet behavior. That is it.

[davidsog]

It was too much trouble to quote the second sentence in that two sentence paragraph?

You mean this one, John?

Due to the absence of interference by the initial jet, the structure of the muzzle jet was more regular than that in Case 1.

Nobody is lying to you, John. Please stop with the accusations.

[JohnKSa]

You mean this one, John?

No. I thought you might have some trouble so I actually quoted the entire paragraph again. I guess you had more trouble than I thought you would.

Here are both sentences again. Try harder this time.

Sorry, that's a lie. The real-world observations from the report (no modeling involved) demonstrate that the muzzle jet is moving faster than the bullet on exit and therefore disprove your claim.

The real world observations say nothing about anything impacting the flight of the bullet.

So what. It's not what they don't say that's a problem for you, it's what they DO say.

It does not negate what they are doing in building their mathematical model.

Nor does it have any relevance to the issue at hand.

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.

From the real world observations in the report.

"...the velocity of the gas ejected from the muzzle exceeded that of the moving body..."

" the high-temperature and high-pressure gunpowder gas inside the tube was quickly sprayed out to chase and surround the moving body."

Clearly the gas can travel faster than the bullet.

No math or figures required to see the contradiction, no dancing around the obvious clash between reality and your claim, no way to eliminate it with verbiage. There is a stark and totally unavoidable contradiction between the real world and your statement.

That is the sticking point. That's what's brought us to this juncture. You can't pretend it's due to some deficit in my knowledge. There's no need to be a scientist or a genius to see the difference between your statement and the real-world observations. To see that only one of them can be true and that the other one must therefore be false.

[davidsog]

No math or figures required to see the contradiction,

The contradiction that there is a lot of secondary explosions going on outside the muzzle?

What contradiction are you talking about?

Simply put, you have confused the properties of the muzzle jet in isolation with what happens when we put it all together.

It is not surprising as you won't even acknowledge the basic physical properties of Normal Shock or any shock formation for that matter. Doing that would go along way towards lending insight into what is going on.

[Mal H]

I'm going to make an executive decision here, and close this "debate". It seems like it could go on ad infinitum, and it already has gone on ad nauseam.

The original question in the thread was adequately answered in the first few replies.