quote:
"It is a given that Warrior cannot tell the difference between momentum, energy and SD. So I took his post to the SD thread and fixed it along the way. I had to fix it because only Warrior could think that a form factor of .523 is better than a form factor of .536 and then build a statement on it "proving" how right he is, winding up all wrong." ... Gerard

Gerard,

Yes I do believe that a lower numeric value for a form factor is better, since we are dividing with it in the equation of BC = SD/i. By dividing with a lower figure (or fraction) we drive the BC value up, not so?

If you still have any doubts about the logic, go look on page 114 of the Speer Reloading Manual No. 12.
There you will see an example of 4 different .308 150 grain Speer bullets:

i = .843 iro a Flat Point bullet
i = .741 iro a Grand Slam bullet
i = .581 iro a Spitzer bullet
i = .534 iro a Spitzer BT bullet

Clearly the most aerodynamically shaped bullet, the Sptitzer BT, has the lowest numeric value, but it is the most efficient of the lot or sleekest if you will that will encounter the least drag in the air.

So it then appears that I am actually right Gerard, and that I am not the only one that thinks this way.
So there is nothing wrong with what I posted and why the military has gone that way.

You should also note that I confined my self to one brand of bullet that the military is using and not different brands that have different shapes that could alter the final BC as we all well know. And yes we can still get a high BC on a light but very sleek bullet with a low NUMERIC VALUE for a form factor.

Warrior

9 pages....I didn't think you could stack SD that high

quote:

Originally posted by 465H&H:
WhatThe,

Your following quote.

quote:

"A study commissioned by the United States Army regarding anti-personnel bullets shows that besides sectional density several other parameters determine bullet penetration. However, and only if all other factors are equal, the projectile with the greatest amount of sectional density will penetrate the deepest."

So I hope one will regard cross section, and non-directional density (in whole or part) along with "retained energy" to provide more detailed penetration of any given mass.

For those who continue to believe, think or otherwise insist that SD plays a significant role in substratum/mass penetration, needs to stop spewing bull-snot all over these boards and shimmy down Yuma way for a spell and tell the worlds finest munitions engineers they are all full of B.S., then explain to them as you have on these boards how they are wrong!

With all due respect it appears that you are carrying their results beyond what they said and making determinations that they never made.
The way I read their results, is that SD does play an important role in penetration but that there are several other factors that also determine penetration depth. A non-inclusive list would include velocity, bullet weight, bullet construction, nose shape and caliber. None of these act alone but work together to produce a result in penetration depth. Another factor that has not received adequate consideration here is the type of media that the bullet penetrates. Whether it is simulated media or live animal tissue and bones.

465H&H

Due respect taken, The problem herein lies a single problem. That problem is the fundamental relationship density plays in a moving object. Once in motion density at all levels is reduced by stabilization and the balance is then mass. distribution of density while in motion is centrifugal but all the same, not recognized by mass as no theory applies. Penetration is far easier to calculate with any given substrate as you have mentioned with the simple formula M(v2)=Ke(C/Pe)-resistance of substrate. Where substrate resistance is measured by and in itself i.e. Fm(*d)=return foot pounds of energy. In addition you have the basic design of the bullet hence, BC×{v²}×R(¡)². There is no practical formula to measure mass breakdown or the destruction of a projectile in or on any given substrate so field testing and analysis is required. We can always use (POI) energy to compensate for residual Ke but the mass is already effected therefore, any solution is going to be (+/-), this is wear all things are not equal because SD never played a role other than maintaining Ke while in motion at a "designed in" specific section as designed by the bullet maker him/herself. In addition, I'm fairly convinced that some here don't really understand just what SD is. Unfortunately, the term SD is used in many publications in place of "mass" where it becomes instrumental in the layman's mind. SD is out the window when the projectile moves, then it is simple mass. The placement of density in any projectile is to center and "cross counter" a projectiles point of balance to achieve a desired flight characteristic i.e. "nose up" / "nose down". It just has no role in penetration other than the fact it is simple mass at the point of impact! Plan a simple fact!

Hey, Karl, Launge, and Mr. G...I tried...)"(

WhatThe,

Impact physics is the approriate branch of science to be applied to explain bullet behaviour in the penetration event. Shapeless mass or varing shapes have different penetration properties:

'Ball' vs 'Bullet' vs a 'Flat Penny' - all equal to say 500 grains shot at say 2,250 fps and for simplicity let us make it non deformable brass. Which one will penetrate deepest? More mass behind a given surface area, such as in the bullet will ....



Warrior

Warrior
You are a clever and knowledgeable man. I could learn a thing or two from you!

I will confess however, that I do not have a clue what the graph shown means.


WhatThe
Same applies to you.

You Folks hold me in awe!

Warrior,
You should be getting that sinking feeling about now.

303Guy,
Forget about Warrior. He also has no idea what the chart above means. WhatThe has good information but Warrior does not recognise good information when it is handed to him on a plate. So, do not be fooled by a front with nothing behind it.

quote:

The problem herein lies a single problem. That problem is the fundamental relationship density plays in a moving object. Once in motion density at all levels is reduced by stabilization and the balance is then mass. distribution of density while in motion is centrifugal but all the same, not recognized by mass as no theory applies. Penetration is far easier to calculate with any given substrate as you have mentioned with the simple formula M(v2)=Ke(C/Pe)-resistance of substrate. Where substrate resistance is measured by and in itself i.e. Fm(*d)=return foot pounds of energy.

I wish he'd brought this out to begin with instead of all the flaming and trolling and insulting he appeared to be doing initially. It was pretty reasonable to think that he otherwise didn't have anything to bring to the table. I see now I was must have been wrong. If so, my apologies, for what that's worth. I might have even begun to understand some of that by now with just a few relevant followup posts. For instance, I don't understand the definitions of some of the constants he used, but I suppose I'll find out eventually, here or elsewhere.
After all, like I've said on so many occasions, I am no expert. I'm still just a student despite my age, but I do want to get it right. I don't mind throwing concepts and theories in the garbage when they no longer have any use or are misapplied. But I first need to know why and how. Insults and stupid cliparts aren't going to tell me why and how.
Not too much to ask, I hope.

OK

Enough

Gerard and Warrior--

You both have points to make-and I am sure are good chaps over a pint, what ever in the hell that Brit means. But your continual pissin match ruins ANY conversation for all of us.
You dont have to agree but stop the damn sniping. The rest of us seem to be able to generally have a civil conversation. If the continent of Africa isnt big enough for your arguement go to mars or to Hell.

i am asking in the Moderators.

You dont have to agre but quit the back and forth bitchin. None of the rest of us can use a thread once you two Idiots get involved.

Grow the fuck up--its the internet for gods sake. Sell tickets in JO'berg and we will bet on the fight. Just quit messin us up.

SSR

And to show I am a fair man-

I hope to be in RSA in November hunting with AUBS458. If anyone wants to take issue with me I will stand a round and we can work out what ever we need to. But grow up you two. You are bothering the adults here.

SSR

Cross L,

Just on this very page you can scroll back and see how Gerard plays the man rather than the ball - you can go back to previous pages and see the same all the time his agenda of belittling. Just do yourself that favour and check ... and that is sniping ... his very attitude to continually come with personal insults and attacks.

Anyway, you are welcome to meet up with me when you set foot here in SA, you just need to drop me a PM and tell me where you are, and I will come to you to make it easier on you.

I much prefer personal discussions as a general rule, as people are then much less inclined to take liberties and throw insults around from a position of safety behind their their PC's as Gerard does.

You will also noticed that I did not even answer Gerard on his last insult, as I am trying to ignore his continual insults and condescending talk, but at some stage one is compelled to answer.

Warrior

quote:

M(v2)=Ke(C/Pe)-resistance of substrate. Where substrate resistance is measured by and in itself i.e. Fm(*d)=return foot pounds of energy.

I think WhatThe is teaching us what I was talking about here or somewhere else when a discussion of kinetic energy came up. I'm just not sure what the constants mean. But if I read correctly, I think he's using kinetic energy and the resistance (what I called resisting force.)
I could have misunderstood, though.

Glenn,

I would venture to say that if you do not fully understand, then a good 80% does not understand. To be fundamental, a lecture is actually a lesson for students that must still get to grips with the concepts and principles and not directed at those who are at a level who have already a masters degree and getting pointers for a doctorate in science.

I would welcome a proper lesson for the 80% that includes me, of how SD works in the 3 spheres of internal ballistics (in gun), external ballistics (in flight) and terminal ballistics (in target). A proper lesson would assume we know little, and then it is built up step by step to its logical conclusion to take all students along to make the information our own. Giving data is not good enough, as it is raw. Raw data must be converted to usable and structured information. Shared information then again becomes common knowledge that can be applied by the students, or in our case by the hunters. Essentially we are hunters that need a practical application.

That is why I suggested that the branch of science should be impact physics and not based on the relativity model of Einstein. And so we should lean more on the work of Leonhard Euler, but in context of rifle ballistics (Continuum mechanics) as we know it today at rifle velocities, that deals with the analysis of the kinematics and the mechanical behavior of materials modeled as a continuous mass rather than as discrete particles.

Warrior

Cross L, you are not aware of the history behind this. Do this one little test.

Warrior stated in the post above:

quote:

And so we should lean more on the work of Leonhard Euler, but in context of rifle ballistics (Continuum mechanics) as we know it today at rifle velocities, that deals with the analysis of the kinematics and the mechanical behavior of materials modeled as a continuous mass rather than as discrete particles.

Google the following. Use the entire 24 word piece:

"that deals with the analysis of the kinematics and the mechanical behavior of materials modeled as a continuous mass rather than as discrete particles."

Then ask yourself: Does Warrior know what he is talking about, or is he an accomplished GoogleFu con artist. He fools most of the people most of the time.

Warrior has ties to another manufacturer and has made it his business to slander GSC and myself. He has been in my face for the last ten years with his lies, slander and junk science. Would you tolerate that?

Notice a couple of facts: I only respond when Warrior starts a scrap that involves GSC, GSC product or my person. I never instigate, only react. In 2009 I started taking these exchanges out of the relevant threads to minimise disruption. Warrior does not follow suit because he wants to keep his slander as public as possible. What I do not understand is why he is not ostracised for this. So, by way of experiment, this time I placed my responses here. This is a thread I started before you joined this forum , so you would not know about it. From now on, I will respond there as I have always done. Let us see if Warrior follows.

Also note that Warrior lies as it suits him. He plays to the audience of the moment. Proof:

quote:

Warrior states: people are then much less inclined to take liberties and throw insults around from a position of safety behind their their PC's as Gerard does.

This is hiding behind a PC? There is even a gps location where I can be found in person.

quote:

Warrior states: Just on this very page you can scroll back and see how Gerard plays the man rather than the ball - you can go back to previous pages and see the same all the time his agenda of belittling. Just do yourself that favour and check ... and that is sniping ... his very attitude to continually come with personal insults and attacks.

Here are quotes where Warrior addressed or discussed me, from this thread alone. They vary from personally insulting to downright lies. His quote above, is a lie:

quote:

The crackpot I am refering to is to deny SD a role in terminal performance.
-----------------------------
Yes Gerard, you are being profoundly stupid with your crackpot reasoning and your skew interpretation. What a farce and a pathetic reply
---------------------
40 inches of barrel is the figment of your imagination.
-----------------------
Your pearls of wisdom is quite something.
----------------------
I am sure you found Gerard's latest comment hilarious
-----------------------
Just to enjoy it once more, this is the kind of logic and reasoning pattern ... Gerard is honestly and seriously suggesting that 3500 fps can be obtained with a 40" barrel in a 7x57.
-----------------------
You offered the above as a solution to get the momentum value up - how idiotic !!!
Totally removed from reality.
-----------------------
perpetuating a crack-pot theory like Gerard Schultz for the sake of promoting his own light-for-caliber bullets
-----------------------
Rasputin,

Sd is just a practical joke.

Don't forget to take your pills.


-------------------------
YOU HAVE TO RUN A MARKETING CAMPAIGN WITH REGARD TO YOUR LIGHT FOR CALIBER HV BULLETS
---------------------------
This is the cardinal stupidity that I am warning about, you just don't seem to get it.
---------------------------
don't waste your time to engage in senseless debate with Gerard Schultz, it is a futile endeavour.
----------------------------
only he knows how to present theory,
----------------------------
that is bested by his phenominal experience of shooting game by the thousands and consuming a major part of the kill like a pack of lions.
------------------------------
Gerard's final opinion on SD that is coming through so profoundly and idiotically
-------------------------------

I said early on that "this thread is divided between those who have a solid ballistics background, those who repeat folklore (and Grandpa's gut feeling) and those who are searching for answers. Strange that I find myself in the first group and you, Warrior, are firmly in the second, doing your best to mislead the third."

To whom it may concern:

A very one sided presentation here by Gerard, and I will answer the cry baby in between:

quote:
The crackpot I am referring to is to deny SD a role in terminal performance.

The crackpot is the theory of denying SD
-----------------------------
Yes Gerard, you are being profoundly stupid with your crackpot reasoning and your skew interpretation. What a farce and a pathetic reply.

Crackpot reasoning is indeed stupid and when making skewed interpretations are indeed stupid and so it does become a farce. Gerard is known for making skewed interpretations of what I did not say or meant - very simple.
---------------------
40 inches of barrel is the figment of your imagination.

Bring up a 40 inch barrel in this discussion as a solution can only be a figment of a wild imagination as it is not workable.
-----------------------
Your pearls of wisdom is quite something.

Yes, in realtion to the 40 inch suggestion, I am in awe at this originality, which is best described by pearls of wisdom.
----------------------
I am sure you found Gerard's latest comment hilarious.

Yes, I did find it hilarious, down right laughable Gerard.
-----------------------
Just to enjoy it once more, this is the kind of logic and reasoning pattern ... Gerard is honestly and seriously suggesting that 3500 fps can be obtained with a 40" barrel in a 7x57.

Yes why offer such outlandish impractical suggestions to prop up a weak argument.
-----------------------
You offered the above as a solution to get the momentum value up - how idiotic !!! Totally removed from reality.

Quite so, I still cannot believe that you offered such such a non event as reality.
-----------------------
perpetuating a crack-pot theory like Gerard Schultz for the sake of promoting his own light-for-caliber bullets.

You advertise on your website that SD is a prcatical joke and I do indeed regard that as a crackpot theory. Promoting light for caliber bullets is in opposition to high SD bullets, not so?
-----------------------
Rasputin,

You have called me many other names, do not be so one sided Gerard - you know better. Did you not refer to me as .... "Pontificus Ignoranus"? You are running an agenda of slander against me to ridicule me at every turn.
------------------------
Sd is just a practical joke.

Yes, that is stated on your web site, not so? Are you having a memory lapse?
------------------------
Don't forget to take your pills.

Your paranoia that that I have someting against you, when in fact I have told you a thousand times that I differ with you in philosophy and the theory of light and fast bullets versus heavy and slow. Accusing me of faking a test by massaging the results. Then you must be off your pills to say something like this.
------------------------

Then you come with your statements that you are not mentioning either so as to portray a very one sided position:

Are you in a dark place or what?
You are so murky on the subject of SD and penetration
Not enough grasp on the facts?
It is only silly if you are incapable of dealing with multiple concepts
given your confusion around the concepts?
However, I would not expect that you would understand this.
Still no answers. Cornered again on your crackpot theories, just like before.
I am amazed at how many members you duped with that one.
You get a kick out of pretending, don't you?
Telling me I lie when all my figures are published and the velocity goes up on lighter bullets - another skew interpretation.
Now the spin to try and save the lost cause: (There is no lost cause - SD is for real, without SD we do not have bullets.)
Speaking about how dumb it is to down load, I recall you saying that down loading improves performance. (another out of context quote)
Stupid is as stupid does, or is it Warrior speak with forked tongue.
Goodness, your experience is limited
You miss the point so well, one would think they give rewards for point missing.
But your rabid lack of comprehension does not stop there,
You should be getting that sinking feeling about now.
To 303Guy ..."Forget about Warrior" (soliciting support and to show me down)
It is a given that Warrior cannot tell the difference between momentum, energy and SD.
Warrior does not recognise good information when it is handed to him on a plate
So, do not be fooled by a front with nothing behind it.

Then the continual lie that Gerard perpetuates that I have ties with another manufacturer. I am a customer of various bullet making companies - no more and no less. He has been told this a thousand times.

Gerard must really be thinking that he smells like roses.

Warrior

Sectional density maters, but to me bullet construction is more critical depending on the game intended to take, at the distance to take the game at, and the velocity of the projectile. If I am using a magnum and going after elk, traditionally taken at 100 yards or less most of the time, I would choose a bullet on the heavy side and of great construction. If you are using the same weight bullet with the same sectional density and have two different outcomes as far as,penetration and initial shock (energy transfer).

Well, this has proven to be quite a discussion, ruffled feathers and all, but I'm cashing in my chips from this one.
I'll see everyone elsewhere, I hope!

warrior and Gerard

BUGGER OFF!!

SSR

I would like to thank all participants discussing SD, and it may just be fitting to close off with words from ALF:

"SD is SD, it is what it is, it is integral to the concept simple Newtonian mechanics, no more no less, you cannot deminish or expand it's value.

Without it there will be no penetration, in fact no physical act of motion of a body through a medium.

What you guys are consistantly doing is to misinterpret what you believe you are seeing. This is the fallacy!

A body that moves in certain direction has mass, it has velocity and based on the spatial distribution of that mass has shape and form and that shape interacts through a certain reference surface area with the medium through wich the body moves.

The ratio of the body's mass to that surface area interacting with the medium through which motion occurs is termed Sectional Density. The ratio of sectional density to the factor of form is called Ballistic coefficient.

It is intergral and central to all 3 fields of ballistics, internal, intermediary and terminal.

Without it you cannot describe the physics of motion. To try and do so would be fallacy.

The motion of what you guys see as modern generation bullets is goverened just as much by SD as any other bullet projectile or body in fight, as much as it always was as much as it always will be !

Sources:

1. The physics and Biophysics of wound ballistics: Bellamy RF, Zajtchuk R
Walter Reed Army Medical Centre Washington D.C.
Chapter 4. from Conventional warfare: Ballistic, Blast, and Burn Injury

2. Scientific foundations of Trauma: Cooper et al. Butterworth Heinemann Publishers First edition 1997 ISBN 0-7506-1585-0
Section 1. Penetrating injury by projectiles Chapters 1-8.

3. Sellier KG and Kneubeuhl BP. Wound ballistics and the Scientific background. Elsevier Publishers 1993 ISBN 0-44481511-2"

Yes, without SD we do not have bullets ... just a shapeless blob of metal !!!

Warrior

quote:

Originally posted by Warrior:
...it may just be fitting to close off with ...

Hey Vapo, Would that be Summary #2 or #200?

Darn shame warrior can't "Dumb it down" for us all like alf always did.

It is already dumbed down.

Regrettably, this is live again.

quote:

Originally posted by Gerard:
It is already dumbed down.

Here is the acid test ... we go buffalo hunting say with a .375 H&H.

The choice is a 155 grain vs 265 grain bullet.
For the sake of the discussion let us take the 155 grain KJG bullet from Lutz Möller; a copper drive band bullet that is CNC machined and compare it to the 265 grain GS-HV bullet.

Before we exercise our choice, let us first see how the 155 gr KJG bullet performs in a wetpack - ignore the first bullet in the photo being a Hornady Interbond bullet:



(The key to using ribbed bullets is your barrel dimensions have to match the bullet so that the body of the bullet should ride on top of the lands and the ribs fill the grooves to give you a gas seal.)

It lost its front nose to form a flat-nosed cylinder by design, and so lost 28.75% of its weight to retain 110.5 grains. Now would this low SD bullet (SD=.157), which can be driven at a very high velocity, be ideal for buffalo hunting?

Now if "increased SD is useless" as contemplated by Gerard, then this bullet should be fine, not so?
But no buffalo hunter in his right mind would pick this bullet, as the increased velocity can never make up for lost momentum.

Clearly the heavier 265 gr GS-HV bullet with its higher SD is a much better choice.
We could also argue that Lutz Möller makes a 265 gr KJG bullet for a fairer comparison.
Buffalo hunters would be more inclined to opt for the heavier bullet, even if it were to lose the same percentage of weight.

This is proof that SD is relevant.

And so it goes .... that the new 340 grain Rhino Solid Shank bullet (SD=.345) that retains around 98% in buffalo and open up to 2.4x original diameter, is an even better choice.

Now SD is also dynamic in target ... the bullet can lose all its petals in the first few inches, way before reaching the vitals, and progress essentially as a lighter FN solid at original diameter or a fraction bigger as we see in the photo, or it maintains its petals at say 2.4x expansion with negligible weight loss.

And so "Dynamic SD" (in target) is even more important than pristine SD, but you have to start with some SD, and the choice is yours - do you want to start with 155 grains, 165 grains or 340 grains.

And so SD and Dynamic SD plays a very important role as to its effectiveness.


Rhino 375 Cal - 340 gr - ST108 (first 2 bullets)

Warrior

Here is a selection of high-SD bullets from Rhino Bullets:



Hi Kobus,

Recovered bullets shown in photo as follows (from left to right):

458 – Swift AFrame, 500gr, wetpack
458 – Rhino 485gr, wetpack
416 – Rhino 430gr, wetpack
416 – Rhino 430gr, zebra
416 – Rhino 430gr, Buffalo
416 – Rhino 430gr, Buffalo
416 – Rhino 430gr, Buffalo
416 – Rhino 430gr, Buffalo
416 – Rhino 430gr, Buffalo
416 – Rhino 450gr, Buffalo
416 – Rhino 430gr, unfired
416 – Rhino 450gr, unfired


That 450 gr 416 after first test appears to be perfect, velocity was about 2,200ft/sec.

The velocity for the 430 gr’s/416 was 2,300ft/sec

Regards,

Richard Sowry

Here are pictures of the result of low SD bullets from GSC:

308Win 130gr



22x64 40gr



22x64 40gr



500NE 540gr



416 Rigby 380gr



25-06 85gr



Unfortunately no bullets were recovered, they all shot through.

This one resulted in a bullet recovery. Eland at 200m with a 308 Win and the 130gr HV.

quote:

Originally posted by Gerard:
Here are pictures of the result of low SD bullets from GSC:

308Win 130gr



22x64 40gr



22x64 40gr



500NE 540gr



416 Rigby 380gr



25-06 85gr



Unfortunately no bullets were recovered, they all shot through.

This one resulted in a bullet recovery. Eland at 200m with a 308 Win and the 130gr HV.

The 540 grain .510 bullet has a SD of .296 and the 380 grain .416 a SD of .313. Those are hardly low SD bullets.

465H&H

quote:

Well, this has proven to be quite a discussion, ruffled feathers and all, but I'm cashing in my chips from this one.

Unless I change my mind.

quote:

Here are pictures of the result of low SD bullets from GSC:

Now I understand your objections to SD. Low SD does not always mean low performance. But I pretty well knew that already.

From my experience, a lot of handgun bullets have a very low SD, but a number of them are capable of taking some sizeable game. Against my local whitetails, I would much prefer a low sectional density .44 Magnum handgun round to a high sectional density .243 rifle round any day of the week.

I haven't used GSC bullets or anything like them yet, but I wouldn't think twice about it. I could understand that copper/brass expanding bullets might hold together and retain mass better for increased penetration.

As we say, there is more than one way to skin a cat.

quote:

The 540 grain .510 bullet has a SD of .296 and the 380 grain .416 a SD of .313. Those are hardly low SD bullets.

For the 500NE, which would have the lower SD? A 540gr bullet or a 570gr bullet?
For the 416 Rigby, which would have the lower SD? A 380gr bullet or a 400/410gr bullet?

What are the "traditional" bullet weights for these calibers?

Would one call lower weights than the "traditional", low SD bullets and, bullets that are heavier than "traditional", high SD bullets?

If the "traditional" bullet weight is already a low/high SD bullet, would a lighter bullet be a low SD bullet or a lower SD bullet. Or would it be a lower high SD bullet? This is an aspect of SD I have not considered yet. Interesting.



BTW, I forgot to mention this result: 345m with a really low SD bullet (0.120). Through and through so, no recovered bullet.

quote:

BTW, I forgot to mention this result: 345m with a really low SD bullet (0.120). Through and through so, no recovered bullet.

Just curious, Gerard. What bullet was that?

40gr HV from a 22-250 at 4200fps.

Full story is here.

Thats NOT a really low SD for a 22

SEE your own post RE traditional weights just above

And questioning whether a bullet is high or low SD accordint to whether its traditional or not hardly is a reasoned scirntific answer or rebuttal

SSR

I would think that 40gr is on the low side for a 22 cal as they mostly run with 50gr C&C bullets. Certainly, if one adheres to the dictum of "penetration comes with SD", a sectional density of .120 is nowhere. Fortunately, SD figures only very occasionally in calculation and I do not regard it as a pointer to performance of any kind. My thoughts on SD above were not intended as a scientific answer or rebuttal. It could not be, because SD (as a number) plays no role in determining how a bullet will behave or perform.

I note elsewhere that 485 and 500gr .458" bullets are described as "high SD" bullets. Would that be correct? I have not taken much note of high or low SD, as SD is a non event in the big scheme of things for us. We regard construction, initial shape, deformed shape and the designed control over the deformed shape as the important factors in terminal performance.

quote:

40gr HV from a 22-250 at 4200fps.

Oh, yeah! A friend of mine loves a 22-250 for deer. He bought some metallic silhouettes to use as targets. The 22-250's went right through them as if you'd used a drill!

The 22s are very much underrated, mainly as a result of frangible bullets. Feed them with a bullet that is designed to work at that level of speed, and you have something that fights way above it's weight class.

My favorite culling machine.

http://forums.accuratereloadin...101069251#2101069251

Warrior

rcamuglia:

quote:

and if the lighter aluminum ball is fired at an increased velocity to give it identical momentum to the lower velocity lead ball in the given problem, that penetration will be identical?

Gerard:

quote:

Reducing speed (2) for a given weight (1) will reduce momentum (2), energy (2) stagnation pressure (2) and so on and vice versa.

Theoretically, by increasing the speed (2) of the aluminum (1) ball (1) to 4.5 times that of the lead (1) ball (1), momentum (2) can be equaled. All we can say for sure is that, although momentum (2) will be equal, the other factors (2) will be so far from reality that any attempt at guestimating an outcome would be impossible. Also take note of the 'and so on' above, because the knock on effect of changing a parameter (1 or 2), extends beyond what I have mentioned there by way of example.

What remains as fact is that:
Penetration (2) can be increased or decreased without changing SD (1).
Penetration (2) can be increased or decreased when SD (1) is increased.
Penetration (2) can be increased or decreased when SD (1) is decreased.
Like weight (1), length (1), diameter (1), specific gravity (1) and a host of others, SD (1) cannot be regarded as linear to any performance parameter.

In the illustrations that Warrior put up, especially the last two, there are some mistakes. These must be very old or done by someone who is not sure about the right terminology.
Taking them one by one, can those who believe that SD drives penetration, explain the information highlighted with the green arrows in the first one?



In the second, apart from the mistake in the Legend, the heading is also wrong. Testing the mass density by varying the mass density as well as the diameter of the balls, create too many variables. The heading should have been: Illustration of Variation of Mass Density and Diameter of the Projectiles. Had the diameter been kept the same for all three, and only the material density changed, how would that affect the results?



In the third illustration, apart from the mistake, one must take note of the arrowed information about m/A. To further illustrate the non event of SD, consider how a change of shape on the nose of the bullet 2, would change penetration depth. Keep all the same, as it is, but put a typical flat nose on one bullet, a cone with a sharp point on another and compare it to the round nose. Will the penetration depth change? Has the SD changed? Does the drag change?



Five years ago the same mistakes were made. Those who believe that penetration follows SD were proven wrong then and now the same is happening again. Learn from history guys, the laws of physics do not change if the wrong theories are repeated often enough.

http://forums.accuratereloadin...641070351#4641070351

Warrior

We need to re-invite the others to the party.

I have some comments to make about the illustrations based on my own research and observations.

#1 (mass and area constant, velocities increased, penetration decreased, drag increased) I think I understand that there be a point where penetration suffers due to velocity, but I think there's no denying that there is a point, or a range, where penetration actually benefits from velocity. So I'm not entirely sure about this one. I would like to see some testing of this.

#2. This is interesting because we have 3 balls of three different compositions. Aluminum, iron, and tungsten. Mass and velocity are all the same, so momentum is constant. Since the aluminum ball is the least dense, you would have to have a ball of the largest diameter to equal the mass of the other two balls. This means that surface area wil be the largest. Therefore the ratio of mass to surface area will be the least. The ratio of mass to surface area is exactly the definition of sectional density to my understanding. Penetration in this case is shown to be the least of the three.

#3. We have two different projectiles. A round ball and a roundnose bullet. Both have the same composition, a lead-antimony alloy. Mass and velocity, hence momentum, are exactly the same. Other than the differing shapes of the projectiles, you have the same situation as in illustration #2. The same mass, velocity, energy and momentum, but a larger surface area with the ball and a smaller surface area with the bullet. The one with the smaller surface area is shown to penetrate the deepest. Again due to the larger ratio of the mass to smaller surface area.

From this I think it's easy to understand why there are those of us who favor sectional density, in its true sense, as one of the prime factors in penetration.

Gerard,

Is M/A = SD incorrect?

rcamuglia,
Why do you ask?

Never cease to amaze

SSR