Author Topic: Velocity, and what we need to know!  (Read 871 times)

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Offline K-Texas

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Velocity, and what we need to know!
« on: June 14, 2018, 09:19:23 PM »
A question was raised about my understanding of exterior ballistics. I can assure you all that there are some very worthwhile industry professionals who court my opinion from time to time.

First, understand the Speed-of-Sound, or what aeronautics refers to as Mach, changes with altitude. The higher the altitude when you are shooting, the less speed to reach Mach 1 is required. When I'm doing such calculations, based on shooting at our local range where probably no one can give me the correct altitude, I've worked with enough topographical surveys to be comfortable with 1350' above sea level.

But, as far as bragging rights for whose new jet fighter is fastest, those speeds/velocity generally come at very high altitude.

As handgunners, the two velocity ranges we are most concerned with are Sub-Sonic, and Super-Sonic. By true definition, while considering altitude, the difference theoretically can be as small as 1 FPS. For practical reasons, we should probably be concerned with a bit more than 1 FPS.

Now, with the proliferation of sound-suppressors, the highest Sub-Sonic velocity is what should be considered. Some of this goes back a ways to the adoption of the HK Mk 23 SOCOM pistol. There were some very worthy competitors for that contract where HK finally won because they convinced the pencil pushers that they could provide the only pistol where the slide could be locked for a single-shot suppressed round. Well, HK got the contract, but never delivered on the capability of firing a round with no movement of the slide to displace recoil. The .45 ACP was chosen because it had the highest weight capability at sub-sonic velocity.

You can google all of this, just don't expect a finite solution. So, I'll just say that super-sonic velocity at sea level (Mach 1) is around 1120 FPS. For those who have read the article I last wrote for Western Powder Co., you may have noticed that 3 of the 4 147 gr. 9mm JHP loads I was working with all proved to be more effective than the Hornady 230 gr. +P XTP load used in Charles Schwartz's testing. All but one area, and that being momentum due to the vastly heavier 230 gr. XTP. As far as P[I/H], probability of incapacitation per hit, things are different.

Specifically dealing with the term Trans-sonic, the root of the word is much as you would imagine it: a transition. In this case, the transition from Super-Sonic velocity to Sub-Sonic velocity. The trans-sonic velocity is exactly that: +/- 0.2 Mach, or from 0.8 Mach to 1.2 Mach. Even at sea level we're talking around 450 FPS as velocity change +/-. As far as any ballistic significance, I'll leave that up to people more interested in making an impression with a $10 word where a 5 cent solution covers it pretty well. Bullet drop and drift, of course, are attempting to defeat greater atmospheric conditions at lower velocity, but that pretty much begins when the bullet leaves the bore. Moreover, a number of factors should be considered, chief among them the ballistic co-efficient of the bullet itself with a consideration of the velocity it travels. These things, I hope, are still covered in handloading manuals. They are very specific to me, personally, in selecting the best bullet for a specific handload's performance while considering a number of factors including energy.

Lately, 6.5mm cartridges are all the rage, and probably for good reason, because they can combine very high Ballistic Co-efficient bullets that get most jobs done at lower velocity, and thus, lower recoil; always a benefit to the shooter in putting rounds where they need to go. Few cartridges smaller or larger are capable of achieving such a balance. Me personally, and being a very experienced handloader, my ears kind of perked up when I found out that Lapua was offering 6.5 CM cases with small primer pockets. That created a question that so far I've failed to ask those I have confidence in since Starline is also offering 6.5 CM cases with a small primer pocket. When I do remember to ask whom I consider the expert on anything 6.5mm, I'll post. Until then I'll just say that my supposition says that a small primer should produce lower pressure than a large primer. If that holds up, there is the possibility that slightly higher powder charges can be used with the small primer.

Actually, I'd like to see the same thing done with the .260 Rem. Unfortunately, the SAAMI spec is 60,000 PSI while the smaller 6.5 CM was allowed 62,000 PSI. In my own experience, and considering all of the variables, including throat erosion, I believe that the .260 Ackley Improved might be the best of the bunch. I once had high hopes for the 6.5 x 284 until we ended up with 2 different versions. The original, known as the 6.5 X 284 Winchester worked in short-action rifles while Norma developed their cartridge (the more common of the 2) for a standard action, and ballistically, only the slight advantage in BC is worth considering vs the .270 Winchester.  :icon_wink:
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Offline Psyc

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Re: Velocity, and what we need to know!
« Reply #1 on: June 14, 2018, 10:34:52 PM »
I believe you're mistaken K Texas.
The Ideal Gas Law, which precisely describes gas behavior clearly states that c = [k R T]^1/2.
Where
c is the speed of sound in an particular fluid.
k and R are gas constants that describe the fluid (gas) in question.
T is the absolute temperature (such as in Rankin).

Adiabatic temperature generally does decrease with an increase altitude.
But therein lies a potentially fatal calculation flaw.
The temperature gradient is usually non-linear in the atmosphere.
Such as when there is wind or turbulence (or clouds).
There are rough conversion factors for consistent temperature gradients in non-critical calculations.
But there is no substitute for knowing the actual temperature of the medium a projectile is flowing through.


Offline K-Texas

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Re: Velocity, and what we need to know!
« Reply #2 on: June 14, 2018, 11:02:29 PM »
Think I might need to see what you're basing that on. First, air is a gas and I'm not talking about the SoS in a fluid. Please post your reference mat'l or a link to it.  :icon_wink:
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Offline Psyc

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Re: Velocity, and what we need to know!
« Reply #3 on: June 15, 2018, 08:50:15 AM »
Think I might need to see what you're basing that on. First, air is a gas and I'm not talking about the SoS in a fluid. Please post your reference mat'l or a link to it.  :icon_wink:

You are correct air is a gas.
You are incorrect in implying air is not a fluid.
You may want to find a book on "Fluid Dynamics".
"Computational Methods for Fluid Dynamics" and "Fluid Mechanics"  are good.

Air behaves as and is clasified as is a fluid (not a liquid but a fluid) when describing the motion of laminar and turbulent flow.

Please look up the "Ideal gas law" if you are not familiar with it.



Offline K-Texas

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Re: Velocity, and what we need to know!
« Reply #4 on: June 15, 2018, 08:11:32 PM »
I believe you're mistaken K Texas.
The Ideal Gas Law, which precisely describes gas behavior clearly states that c = [k R T]^1/2.
Where
c is the speed of sound in an particular fluid.
k and R are gas constants that describe the fluid (gas) in question.
T is the absolute temperature (such as in Rankin).

Adiabatic temperature generally does decrease with an increase altitude.
But therein lies a potentially fatal calculation flaw.
The temperature gradient is usually non-linear in the atmosphere.
Such as when there is wind or turbulence (or clouds).
There are rough conversion factors for consistent temperature gradients in non-critical calculations.
But there is no substitute for knowing the actual temperature of the medium a projectile is flowing through.

The reason I asked for reference mat'l was to see how you are misapplying it. Then I thought of a text I haven't read in DECADES: Fluid Dynamics, that you were likely to counter with. 1st problem, I can't remember any part of it dealing specifically with Exterior Ballistics. I feel pretty confident that you are not a Handloader. If you were, you'd probably be aware of some excellent explanations of the topic at hand. To be completely honest, I'm probably more recently experienced with Thermodynamics than Fluid Dynamics. And since heat and atmospheric pressure are factors where fluids are not, it appears that you're trying to base your hypothesis on another transitional state like transonic velocity. It, nor fluids have any significance to the topic at hand. You want to give us a formula whereby a Gas goes Fluid, be me guest. I do know a thing or 2 about the complete cycle of converting gases to a liquid state. Why you want to attach some significance of fluids where most of the formulae is concerned with Aerodynamics, and none for Fluid Dynamics is a bit disturbing considering your statement that someone of my experience, 32+ years of handloading without consideration for my study of ballistics and handloading, even before then, as MISTAKEN is a bit troubling. The reason for this post is to assure those interested not be misled while I point out that the best explanation lies in a good handloading manual. While physical science reinforces everything stated in the best explanations.

I hope it's still printed in the Lyman Reloading manuals as it is my 46th Edition; simply entitled Exterior Ballistics by W.T McDonald  & T.C. Almgren. It covers just about every aspect of exterior ballistics from round balls to Spire-point, Boat-tail projectiles in the form of bullets. You might want to read it or another article before you assume someone's incorrect; then making your case with meaningless ambiguity. BTW. this may not go as back as far as Sun Tzu, but it does involve Galileo and Newton.

I did make one mistake I'm sure of: I made the assumption that anyone considering the subject would understand the role that gravity has in this equation. And you know what they say about ASSuming. When you ass-u-me, you make an ass of U and Me.

I'll begin this explanation using the formula for Air Drag Effects and the Ballistic Coefficient. And pardon me for not using the exact characters, but I will type it in a comprehensible way: a = -1/C x Gv, where a is acceleration, C is the ballistic coefficient of the bullet, G is the drag function and v is the velocity of the bullet relative to the AIR!

Coincidentally, I had not remembered that Lyman uses the same velocity that I've given for the Speed of Sound at sea-level being 1120 PS. I was using what I considered to be a good average where different articles will have some +/- as far as the exact velocity.

Excluding Exterior Ballistics in the consideration of the speed-of-sound, I ran across a nice little piece from the National Aeronnautics & Space Adminstration, NASA, where if I can I'll paste the graphic portion as well as the text. If that doesn't work I'll post the textual explanation. :icon_wink:

From NASA:
"Air is a gas, and a very important property of any gas is the speed of sound through the gas. Why are we interested in the speed of sound? The speed of "sound" is actually the speed of transmission of a small disturbance through a medium. Sound itself is a sensation created in the human brain in response to sensory inputs from the inner ear. (We won't comment on the old "tree falling in a forest" discussion!)

Disturbances are transmitted through a gas as a result of collisions between the randomly moving molecules in the gas. The transmission of a small disturbance through a gas is an isentropic process. The conditions in the gas are the same before and after the disturbance passes through. Because the speed of transmission depends on molecular collisions, the speed of sound depends on the state of the gas. The speed of sound is a constant within a given gas and the value of the constant depends on the type of gas (air, pure oxygen, carbon dioxide, etc.) and the temperature of the gas. An analysis based on conservation of mass and momentum shows that the speed of sound a is equal to the square root of the ratio of specific heats g times the gas constant R times the temperature T.

a = sqrt [g * R * T]

Notice that the temperature must be specified on an absolute scale (Kelvin or Rankine). The dependence on the type of gas is included in the gas constant R. which equals the universal gas constant divided by the molecular weight of the gas, and the ratio of specific heats."
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Offline Psyc

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Re: Velocity, and what we need to know!
« Reply #5 on: June 17, 2018, 10:38:16 AM »
And happy fathers day Ktex.

In your quote "From NASA:", I see you are reading NASA's reference pages for Kindergarteners - 12 grade students.
Interesting choice for a reference.

To your implication that gases are not "fluids", the Oxford dictionary defines a fluid as "A substance that has no fixed shape and yields easily to external pressure; a gas or (especially) a liquid."  (So does NASA on their professional level pages.)

In line with Oxford, graduate level fluid dynamics (and that is "Fluid Dynamics" not "Liquid Dynamics") professionals treat gases, most non-viscious liquids and plasmas as fluids.
You can note this in the references supplied.

If you are a teacher, then please seek out the referenced books "Computational Methods for Fluid Dynamics" and "Fluid Mechanics".

You'll be better able to understand with these graduate level text that uses precise computations, not general approximations that intro significant errors with the assumptions you're currently using.

Otherwise, feel free to continue in your bliss.


Offline K-Texas

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Re: Velocity, and what we need to know!
« Reply #6 on: June 17, 2018, 11:48:43 AM »
Thank You, and happy Father's Day to you as well! I think you'll find that if you look a little harder NASA mentioned college students as well. Personally, that covers the limit of my capability since I didn't major in physics and do not have a graduate degree.

Moreover, you want to quibble over the definition of Fluids while they are not mentioned in reference to the speed of sound in the study of ballistics. You supposed my OP was somehow incorrect because I didn't cover the irrelevant.  :icon_wink:
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Offline TXAZ

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Re: Velocity, and what we need to know!
« Reply #7 on: June 17, 2018, 04:05:46 PM »
Psyc,
You are correct regarding Mach calculations.  It's temperature, not altitude that ultimately determines Mach. Standards wise, ICAO defines Mach as 49.0223*(FT+459.67)^0.5, where FT is the Temperature in Farenheit.  That's about as definitive as it gets.

Ktexas blissfully appears to be using some simple formula he found in a reloading manual that uses altitude as a rule of thumb for calculating Mach.  Not precise but it probably works for him.

TXAZ (an Engineer w/ minor in Physics :)  )
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Offline K-Texas

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Re: Velocity, and what we need to know!
« Reply #8 on: June 17, 2018, 06:33:25 PM »
Psyc,
You are correct regarding Mach calculations.  It's temperature, not altitude that ultimately determines Mach. Standards wise, ICAO defines Mach as 49.0223*(FT+459.67)^0.5, where FT is the Temperature in Farenheit.  That's about as definitive as it gets.

Ktexas blissfully appears to be using some simple formula he found in a reloading manual that uses altitude as a rule of thumb for calculating Mach.  Not precise but it probably works for him.

TXAZ (an Engineer w/ minor in Physics :)  )

U 2 need to get a room at the Dumbass Motel! The reason I've given data from handload manuals is because that's what a handloader would be most concerned with.

And let me point out something to you personally Mr. Azz: I was once involved in a design project involving 32 schools in the Lubbock ISD in the late 80s. My designs got a Texas Licensed Irrigator stamp, but the consulting company decided that they needed an engineering firm which kinda rocked the dumbass I worked for that had been born with a silver spoon up his ass. 31 of those systems were utter failures. Wanna guess which one worked? The designer? A 29 year old with a 2 year degree in Design Drafting Technology.

Later, I took a position where I earned additional certifications for Life Safety Systems: Fire Alarm and Fire Sprinkler systems from manufacturers as well as the NFPA. Later, I added another design certification from the BOSE Sound Corp.

In other words, I know a little something about the SOS through different mediums, while on the other hand, where you 2 clowns couldn't construct a decent handload if your lives depended on it. It's engineers like you, working under the lead Architect that convinced the City of New York that the Twin Towers could withstand a direct impact from a Boeing 707; the most common passenger airliner when that project began. Or, the balcony that collapsed in a KC hotel because the structural engineer never considered a greater load need be considered.

And, BTW, even though there were influences on me to become an Architect or Engineer, I chose service to my country first and had a security clearance that none of you demo-commies would come close to qualifying for. If I had my way, no one would even be allowed to enter an engineering degree program without a minimum passing score in Spatial Relationships.

If this question was live, neither of you nitwits could find the simple solution for KE of an arbitrary handload. Hoping you could calculate its momentum would be a fools errand.

It's rather obvious that you both have some pretty serious inferiority complexes. At least Psyc gives some hint about that by his screen name. You, on the otherhand, I noticed (and with your engineering degree) trying to make an impression with a supercilious term, TRANSONIC, which is defined simply as the velocity between Mach 0.8 and Mach 1.2.

Hell, I bet I knew more about Mach in elementary school that you clowns! My life, post that event in Lubbock, has been designing for engineers without a clue, even in their own fields of discipline.

It's dipshits like U 2 that prevent the earnestly interested from learning correct methods. Even at my own risk of being uninvited from this forum, I surely want to express my opinion that the 2 of utes are totally incompetent on anything ballistic.

My original post is correct and was never about fluids. But what you said about only temperature, not altitude effecting the SOS has got to be one of the very stupidest things I've ever read in a reloading forum ANYWHERE. I guess you take for granted that the guys writing articles for reloading manuals do not have any academic credentials???

Rest assured that I took all of the Math and Physical Science courses for an engineering degree. I simply never wanted to be a non-thinking robot for some engineer it took 15 years to acquire the title of Design Engineer! :icon_wink:
« Last Edit: June 18, 2018, 03:27:38 PM by K-Texas »
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Offline Psyc

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Re: Velocity, and what we need to know!
« Reply #9 on: June 17, 2018, 08:01:36 PM »
Thank you Txaz.
I also started out in Mechanical Engineering.
Enjoyed "Reynolds Numbers" modeling if that means anything.
Ended up somewhere else that pays a bit better ;)

K-Texas,
I am concerned with your reactions and words on a semi-anonymous forum.
Lighten up sir.
I sincerely hope you find peace and tolerance (and social etiquette).

Offline K-Texas

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Re: Velocity, and what we need to know!
« Reply #10 on: June 18, 2018, 03:26:31 PM »
K-Texas,
I am concerned with your reactions and words on a semi-anonymous forum.
Lighten up sir.
I sincerely hope you find peace and tolerance (and social etiquette).

So, after disrupting a thread with total ambiguity as your only contribution, you want to be the example of etiquette? You have yet to explain to anyone where my OP was incorrect while you go off on some irrelevant BS that we need not be concerned with in ballistics?

I believe that's a true indicator of who you are, semi-anonymous, seriously ambiguous!

I don't even write under a pseudonym and I'm pretty sure that everyone here can see exactly who I am. One reason for that is that I believe in Col. Coopers maxim to ride, shoot straight and speak the truth.

So once again I ask, how are fluids, or a number of things you think so important, germane to the topic? And further, after I posted the brief statement from NASA, you intentionally tried to mislead those who are reading by stating that it is aimed at kindergartners. Let me refresh your memory by quoting exactly what they said: "This page is intended for college, high school, or middle school students." So are your reading comprehension skills so poor as to miss who was mentioned first as a suggested audience, or did you hope to intentionally mislead with your assertion that the first post was somehow incorrect? The fact is, anyone interested can Google the Speed of Sound and find a number of articles where they need not be concerned about the complexities involved like air qualifying as a fluid. On the topic of ballistics and handloading, it's as I said, IRRELEVANT! Since there is no specific degree for ballistic science or engineering, we rely on individuals that have spent a good number of years in understanding, and hopefully educating. One things for sure, it would behoove both to open up a handloading text and learn some things about BALISTICS above the kindergarten level.

Look, I look at forums as a place where I might be able to help educate, specifically on the topics of handloading and ballistics. NOT as a popularity contest to have an insecurity complex reinforced.

And given the availability of sound suppressors, today, addressing the speed of sound in air, by velocity according to elevation, where your tag-team partner has even tried to dispute that, may be quite a lot more important to the readers than a couple of guys wanting their ego's stroked. :icon_wink:
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Offline Shipwreck

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Re: Velocity, and what we need to know!
« Reply #11 on: June 18, 2018, 04:28:44 PM »

U 2 need to get a room at the Dumbass Motel! The reason I've given data from handload manuals is because that's what a handloader would be most concerned with.

And let me point out something to you personally Mr. Azz: I was once involved in a design project involving 32 schools in the Lubbock ISD in the late 80s. My designs got a Texas Licensed Irrigator stamp, but the consulting company decided that they needed an engineering firm which kinda rocked the dumbass I worked for that had been born with a silver spoon up his ass. 31 of those systems were utter failures. Wanna guess which one worked? The designer? A 29 year old with a 2 year degree in Design Drafting Technology.

Later, I took a position where I earned additional certifications for Life Safety Systems: Fire Alarm and Fire Sprinkler systems from manufacturers as well as the NFPA. Later, I added another design certification from the BOSE Sound Corp.

In other words, I know a little something about the SOS through different mediums, while on the other hand, where you 2 clowns couldn't construct a decent handload if your lives depended on it. It's engineers like you, working under the lead Architect that convinced the City of New York that the Twin Towers could withstand a direct impact from a Boeing 707; the most common passenger airliner when that project began. Or, the balcony that collapsed in a KC hotel because the structural engineer never considered a greater load need be considered.

And, BTW, even though there were influences on me to become an Architect or Engineer, I chose service to my country first and had a security clearance that none of you demo-commies would come close to qualifying for. If I had my way, no one would even be allowed to enter an engineering degree program without a minimum passing score in Spatial Relationships.

If this question was live, neither of you nitwits could find the simple solution for KE of an arbitrary handload.

It's rather obvious that you both have some pretty serious inferiority complexes. At least Psyc gives some hint about that by his screen name. You, on the otherhand, I noticed (and with your engineering degree) trying to make an impression with a supercilious term, TRANSONIC, which is defined simply as the velocity between Mach 0.8 and Mach 1.2.

Hell, I bet I knew more about Mach in elementary school that you clowns! My life, post that event in Lubbock, has been designing for engineers without a clue, even in their own fields of discipline.

It's dipshits like U 2 that prevent the earnestly interested from learning correct methods.
Even at my own risk of being uninvited from this forum, I surely want to express my opinion that the 2 of utes are totally incompetent on anything ballistic.

Ok, K-Texas, you are done here. I Have bolded the specific comments you made on your last thread in order to show specifically WHY you are banned. You should re-read the forum rules that you agreed to when you joined this forum.

Your personal attacks are way out of hand and totally uncalled for.


Forum Rule #2 specifically states:

Quote
2. Please do not be ignorant or use foul/curse language. We eliminated the word censor, but please use common sense... Also, no personal attacks against other forum members.