quote:

Originally posted by deadkenny:
Finally, with respect to terminal ballistics, I believe it is here that the claim of SD being irrelevant is most often made. On the one hand, in theory a higher SD should mean greater penetration. However, that is only completely true for a 'solid', that does not expand at all. It is really bullet performance (along with velocity of course) that will have the greatest influence on this. Hunting bullets are typically designed to 'open', which means the frontal area is expanded and the SD is radically changed. Arguably, a bullet with a greater area (and therefore lower SD, given the same weight) has an advantage here. I tend to agree that velocity and bullet performance are what really count here, and SD does not have the same importance as perhaps it once did in this regard (again, unless you are firing solids that do not expand at all).

Awesome answer. Lets take it 1 step further, (please add to this list and we will compile in the end)
I have a couple (not enough for a real sample) .224 and .308 rounds.
This still doesn't take into account the expansion speed but it gets us a bit closer.

.224 60.0 grains SD .171
mushroomed to and final weight:
.338 51.9 grains SD .065
.280 45.2 grains SD .082
.249 32.7 grains SD .075


.308 200 grains SD .301
mushroomed to and final weight:
.458 162 graims SD .110

quote:

Originally posted by Warrior:
Dear Sir,

I am sorry to tell you what you have written here has no practical benefit, and cannot be considered a proper treatise on the subject, nor have you answered the question as to the role of SD in a hunting scenario in the 3 stages. You are dribbling the ball and nobody can gain any practical benefit whatsoever. So yes, your effort has been a wasted one. The whole way you wrote is one of being a smart-ass and we all are dumb idiots.

To ponder the thought about a bullet gaining a rise in temperature, however minute, during flight and expand (however infinitesimal), and as such, the width of the bullet is now bigger (probably immeasurable), and as such, the SD is reduced is absolute testimony of the irrelevance for the hunter's practical benefit. The incoherent and unstructured way in which you have put it does not help it either, and lacks clarity of thought, showing that you should not be considered a lecturer.

Being a smart-ass, you forgot to mention to me that the bullet weight (the numerator in the SD calculation) is not the same on earth as on the moon, as on the moon it is only 1/6th, and so the SD is different ... like we are hunting on the moon where there is no oxygen and no game, heh? Yes and mass is the same but the weight is less on the moon due to gravitational field. And so we can carry on taking the concept of SD to other planets or the 2 moons of Mars, namely Phobos and Deimos.

Equally unrealistic, one can argue that if we use the bullet (having a SD) in an ambient temperature that the copper bullet would melt, rather than expand, we would also have difficulty is calculating the SD or not being able to keep it the same, heh?

Ponder in your own world, while I will enjoy my hunting and be content with what is practical for me and what works for me in the very same way that Randy Garrett found out what works better for him, even if he stumbled upon the solution. Many things in life has to be determined through trial and error - just like Michael has been doing for the last year with an unbelievable effort even if it is scientifically flawed in some ways.

So, that ends our conversation on this topic, as it is becoming a futile endeavour - we are just not hitting it off, and so be it. Truth be told, it might just be your pompous and condescending way of talk, while you might be a most wonderful and talented person.

Be good.
Warrior

I had a bet with some fellows that you would come back with a response as that above. No one would take the bet except to the contrary. In addition I had a few of them read the entire thread at your return post to my original. While It was suggested that I could have held a practical demo illustrating the principles of density in a projectile that may have been better understood by the layman. At the same time, it was further suggested that while that approach would have seen its way to coherent individuals, you on the other hand demonstrated from the beginning a clear adversarial and defensive position and any approach would have met your defenses all the same. You have in your own opinion have suggested I have failed. You are indeed correct. But let's be fair in that I failed you and you only as others got it very clear which tells me you failed yourself defending something that didn't need defending in the first place. I never attacked your friends claims, his bullets or for that matter anything. In fact I wish him well and a jolly good show. Looking back, I believe this is where your "subjectivity" went out the window along with any rationale.

So to you I say: au revoir `garder l'esprit ouvert.

Let us be sensible and make a Sensible Decison

SD = Sectional Density = Sensible Density = Seriously Dangerous

Sectional density is needed with a sensible higher density for seriously dangerous animals that can hurt you, and it is a matter of going up progressively in SD (as far as stability allows) for the desired effect for progressively deeper penetration within a given caliber (to have any practical benefit) based on your needs and application, and be sensible not to make nonsensical comparisons, appreciating its role in all the ballistic spheres, as something that we cannot wish away as if it does not exist or diminish its role by trashing it as irrelevant in a ballistic sense.

To you I say: One convinced man is already a majority.

Warrior

quote:

Originally posted by Rine Everett:

quote:

Originally posted by deadkenny:
Finally, with respect to terminal ballistics, I believe it is here that the claim of SD being irrelevant is most often made. On the one hand, in theory a higher SD should mean greater penetration. However, that is only completely true for a 'solid', that does not expand at all. It is really bullet performance (along with velocity of course) that will have the greatest influence on this. Hunting bullets are typically designed to 'open', which means the frontal area is expanded and the SD is radically changed. Arguably, a bullet with a greater area (and therefore lower SD, given the same weight) has an advantage here. I tend to agree that velocity and bullet performance are what really count here, and SD does not have the same importance as perhaps it once did in this regard (again, unless you are firing solids that do not expand at all).

Awesome answer. Lets take it 1 step further, (please add to this list and we will compile in the end)
I have a couple (not enough for a real sample) .224 and .308 rounds.
This still doesn't take into account the expansion speed but it gets us a bit closer.

.224 60.0 grains SD .171
mushroomed to and final weight:
.338 51.9 grains SD .065
.280 45.2 grains SD .082
.249 32.7 grains SD .075


.308 200 grains SD .301
mushroomed to and final weight:
.458 162 graims SD .110

Bingo, give the man a hand rolled Havana! You described SD "terminal" effect damn near perfect! Berger bullets used your analogy years ago to pull the ogive and balance point closer to the exit end of the bearing surface to allow less drag. The VLD hunter bullet is a product of this and if I have to use the word sectional density, I will due to the fact it was intended not to be interrupted during penetration and when it reaches the point where disruption is an issue a greater percentage of the entry on soft and medium tissue has already been exhausted. And yes indeed velocity and performance have a much greater effect. However let's change performance to area surface or aerodynamic design.

A+ and Havana to the man!

quote:

I may imply in some instances that perhaps someone is missing something that is right in front of them. Sometimes people need to see the movie twice to get the point, then some people may never get the joke.

quote:

I really hate to say this, but I'm pretty sure, no strike that, I'm confident I have never held a discussion with someone as yourself. The answer has been all but given to you, if it were a snake, you would be at the hospital. I am also confident you haven't bothered to read, absorb or seek this information herein nor abroad as your reply's clearly show that. What is clear, is that you are vigorously defending something you have no knowledge of and that defense has numbed what ever intellect (if any) you may have. Why have you ignored all of my challenges? Had you have even attempted a solution, I would not be here and now chastising you like a rented mule. I have a feeling that you may be one of those with IDD or (Intelligence Deficit Disorder) that lashes out in class to avoid being put on the spot to answer whatever is at question. I saddled nothing but a whahoo that again, knows nothing about the subject and has and continues to avoid visible solutions.

Dejavu to the power of 10

Rasputin,

Sd is just a practical joke.

Don't forget to take your pills.



Warrior

quote:

Originally posted by Gerard:

quote:

lets compare the pentrating capabilities of the 150 vs the 168 vs the 180 TSX. The SD number gets larger right along with the weight denoting greater mass. In this comparison which bullet will penetrate deeper?

1. On paper, they will probably go to very similar penetration depths if fired from the same rifle, say a 30-06, and at similar pressure levels. That is to say if they all expand to similar diameters. If, as is likely in reality, the 180 expands less, it will go deeper than the 150. The same applies to the 168 v the 150. It is not because of the higher SD, it is because of the smaller frontal area that is driven by a similar momentum level in target.

2. SD does not feature when we compare monos.

1. The answer given in the first paragraph does not relate to reality at all, it's only the figment of Rasputin's imagination that is being spinned here to us.

2. To say SD does not feature, is another mis-representation. SD always features in all spheres, and be they Solids or Softs or anywhere in between, SD always plays its role, unless you make non sensical comparisons.

Strange that the above is so totally in contrast with reality and Dr. Ashby's experience that he documented:

Dr Ashby demonstrated on game with Barnes -X bullets that penetration suffers as we increase velocity. With the .223 bullet an increase in impact velocity of only 279 fps (2,369 - 2,090) reduced the penetration by 2.28 inches (16.03" - 13.75"), but at a higher impact velocity of 3,105 fps the penetration reduced by 9.7 inches (16.03" - 6.33"). This is quite significant. After Dr Ashby arrived at his conclusion with the .223 caliber bullet, he was indeed curious to see if the same principle of shallower penetration at higher velocities hold true for bigger caliber bullets as well.

He then proved this trend in the 30-06 and says at 2,792 fps the 165-gr X-bullet penetrates far less deeply than it does at a velocity of 2,428 fps. None at low velocity fail to exit, but at high velocity frequently bullets failed to exit. The he went further and tested the 270-gr .375 bullets at just over 2,400 fps MV on 20 animals (wildebeest, kudu, & zebra). All were deliberately adverse angled shots in the hope to retrieve some of the bullets. All were one shot kills and all bullets did exit.

Dr Ashby has done extensive field work to test and draw some conclusions. He published his findings in the Man Magnum magazine some years back.

Now to make a statement that velocity can replace bullet weight or SD to make up the momentum, is just plain silly. In target drag in flesh goes up to the square of velocity, and so penteration is impaired. Our ballistic system favours bullet weight and that is a fact.

I have done a test in a wetpack - just go here to see that the double caliber expansion of The Barnes-X bullet remain a double caliber expansion from 2,390 fps up to 2,610 fps, and how penetration suffers as SD is reduced.

http://forums.accuratereloadin...691045051#9691045051





Warrior

Are you in a dark place or what? You are so murky on the subject of SD and penetration, that you devote an entire post to proof that SD has no value in mono bullet penetration, while trying to do the opposite. This is almost as funny as when you rabidly agreed with something that Alf posted, only to find that it was something he quoted but disagreed with.

quote:

1. The answer given in the first paragraph does not relate to reality at all, it's only the figment of Rasputin's imagination that is being spinned here to us.

Apart from name calling, why do you disagree with my take on how the 150 and 168gr Barnes will react? Note I said: Why do YOU disagree. Give YOUR technical reason or YOUR practical experience.

quote:

2. To say SD does not feature, is another mis-representation. SD always features in all spheres, and be they Solids or Softs or anywhere in between, SD always play its role, unless you make non sensical comparisons.

You are the one who always insists on comparing same construction bullets when comparing SD. I said SD does not feature when comparing monos - same construction bullets. Now you say "Solids or Softs or anywhere in between". Make up your mind what it is you want, and try to make sense.

quote:

Strange that the above is so totally in contrast with reality and Dr. Ashby's experience that he documented:

How is it in contrast? Are you not capable of understanding what he found and reported? With the examples you quote below, supposedly in support of the importance of SD, you prove the opposite. What a laugh.

quote:

Dr Ashby demonstrated on game with Barnes -X bullets that penetration suffers as we increase velocity. With the .223 bullet an increase in impact velocity of only 279 fps (2,369 - 2,090) reduced the penetration by 2.28 inches (16.03" - 13.75"),

This is despite the fact that the SD remained the same. Excellent proof that SD has no effect in this example. After all, YOUR test proved that the bullets expand to the same diameter. That is about the only thing it proves, the rest is deliberately skewed junk science, designed to give the preconceived outcome you wanted. For a good test, where only speed is varied, not speed and weight as in your effort, go here.

quote:

but at a higher impact velocity of 3,105 fps the penetration reduced by 9.7 inches (16.03" - 6.33").

Thank you for again providing such an excellent example that SD has no bearing on penetration depth.

quote:

This is quite significant. After Dr Ashby arrived at his conclusion with the .223 caliber bullet, he was indeed curious to see if the same principle of shallower penetration at higher velocities hold true for bigger caliber bullets as well.

It is indeed significant because it confirms without doubt that SD does not drive penetration.

quote:

He then proved this trend in the 30-06 and says at 2,792 fps the 165-gr X-bullet penetrates far less deeply than it does at a velocity of 2,428 fps. None at low velocity fail to exit, but at high velocity frequently bullets failed to exit.

This is exactly what I found as well and commented on here. It confirms that, with monos of the same construction, SD without doubt, does not feature as a driver of penetration. Thank you for that.

quote:

The he went further and tested the 270-gr .375 bullets at just over 2,400 fps MV on 20 animals (wildebeest, kudu, & zebra). All were deliberately adverse angled shots in the hope to retrieve some of the bullets. All were one shot kills and all bullets did exit.

On that type of game, almost any mono of any weight from a 375 will exit. Why do you mention this, though? No change in SD, no change in speed, how does this feature as a comparison or example. Confused? Arguing for argument's sake? Not enough grasp on the facts?

quote:

Dr Ashby has done extensive field work to test and draw some conclusions. He published his findings in the Man Magnum magazine some years back.

His exact words were: "At 2,792 fps, the 165 gr Barnes-X bullet penetrates far less deeply than it does at a velocity of 2,484 fps." Now if that is not proof that SD has no bearing on penetration depth, I do not know what is.

quote:

Now to make a statement that velocity can replace bullet weight or SD to make up the momentum, is just plain silly.

It is only silly if you are incapable of dealing with multiple concepts. We know you are challenged in this way. When one considers the multiple factors that drive penetration (9+7+2+5 ring a bell?) and have been waved under your nose for the last two pages, it is quite clear you have no clue.

quote:

In target drag in flesh goes up to the square of velocity, and so penteration is impaired.

Do you think that this is so because "the square of velocity" is in a higher place than "in target drag in flesh" and that one has to "go up" to the other, or might there be another reason for this? Try this link.

quote:

Our ballistic system favours bullet weight and that is a fact.

What does that mean, this quote that you lifted from Alf? Do you understand what he is saying and how do you propose to prove it, given your confusion around the concepts?

Warriors test would probably get different results if either the velocity increase kept kinetic energy the same for all three bullets or the weight reduction was smaller to achieve the same. Less energy in a lighter bullet give less penetration, it is not very surprising.

I will read this again: http://www.riflemagazine.com/m...e/PDF/ri5partial.pdf , you should too.

THE MAIN REASON WHY WE ARE AT ODDS WITH THE IMPORTANCE OF SD IS BECAUSE YOU HAVE TO RUN A MARKETING CAMPAIGN WITH REGARD TO YOUR LIGHT FOR CALIBER HV BULLETS, AS A BREAD AND BUTTER ISSUE AND I DON'T.

SD is the victor in a particular caliber due to higher momentum values through bullet weight, as velocity cannot make up for it most of the time due to certain constrains. That is why our ballistic system favours bullet weight - this is based on my own experience, as evidenced by my own test as stated before, and not as you alluded that I lifted it from Alf - it is more correct to say that we agree with each other on this issue.

Higher velocity with a low-SD bullet meets with more in-target drag.

Lower velocity with a high-SD bullet meets with less in-target drag.

In-target drag goes up with the square of velocity, and it is more significant with expanding bullets as opposed to non expanding bullets - it impairs deep penetration. A good example is bonded bullets that over-expand at too high an impact velocity, and again step the SD up with resultant lower velocity, and bullet performance improves.

Lower velocity causes slower bullet set-up, and so it enhances penetration due to less stagnation pressure, whilst at the same time more mass behind the frontal area is driving penetration. Proof: a round ball vs a bullet (mass must be given shape).

With bullets that are prone to losing weight the lower velocity again helps the higher SD bullet to remain within its threshold strength. Heavier bulllets are invariably shot at lower velocities.

With regard to FN bullets I say the vapour bubble cannot be maintained in the animal, and that is why the supercavitating bubble is a myth, as it is not like homogenous water.

Now you subscribe fully to this theory of supercavitation, I don't and nor does Alf, but you admitted to him, and I quote .... "When it comes to supercavitation, I have relied on Norbert's opinion to explain what is going on. I have only the practical observation of shooting animals with different shapes to guide my opinion without being able to explain why or if supercavitation occurs."

The only way one can tell if supercavitation happens just by observing which shape supercavitates inside the animal and which shape does not, then super natural abilities are needed such as eyes that can do high-speed X-ray scanning at a distance as the bullet is passing through in a micro second. So you observation relative to supercavitation means squat.

"An increase in SD leads to less energy transfer to target per unit distance penetrated and thus deeper penetration. The lower the SD the shallower the penetration, the bigger the energy dump to target and the bigger the TC." ..... Karl Sellier - Shusswaffen und Shusswerkungen.

Perhaps Karl Sellier is also in the dark - yes/no?

In Dan's chart of penetration we have a practical example where a host of different bullets were shot into an elephant, and I will contrast a high SD bullet with a low SD bullet so we can see what happens in real life, and to be fair let us compare 2 monolithic expanding bullets.

High SD bullet - 286 Gr Barnes-X

286 gr @ 2395 fps = Momentum of 97.85, with a weight loss of ZERO, and penetration of 30 inches.

Low SD bullet - 260 Gr GS-HV

260 gr @ 2575 fps = Momentum of 95.64, with a weight loss of 60 grains (23%), and penetration of 22 inches.

Based on this trend the 230 gr HV bullet would have shown even shallower penetration.

And that is the way I see it - over and out.

Warrior

Three simple questions:

1. Which penetrates deeper when fired from the same 30-06 rifle and into the same test medium? A 150gr HV or a 200gr Sako Hammerhead?

2. Which penetrates deeper when fired from the same 7-08 rifle and into the same test medium? A 120gr HV, a 160gr Partition or a 175gr Partition?

3. Which penetrates deeper when a 120gr HV is fired from a 7-08 and a 160gr Swift A frame is fired at the same speed from a 7mm RM, into the same media?

Dan's chart also contains a 286gr NF bullet that went 30", a Woodleigh 286gr that went 20" and a Norma Oryx 286gr that went 11". What does all this prove? It proves that SD means nothing in the terminal performance big picture.

quote:

With regard to FN bullets I say the vapour bubble cannot be maintained in the animal, and that is why the supercavitating bubble is a myth, as it is not like homogenous water.

How do you explain recovered bullets that show no evidence of having contact with the tissue other than at the meplat? There are many ways of observing a phenomenon or analysing a result. However, I would not expect that you would understand this. Thank you for supplying that quote of mine from February 2005. It shows clearly that, unlike you, I have actually learned something in the past six years.

Warrior,

You are probably a nice guy, could probably have fun tossing down a few cold one's with ya and telling some lies. The problem here, is that you're not getting the role of SD at all, not even remotely! And the more you argue your point the more rediculas it becomes.

i.e. "SD is the victor in a particular caliber due to higher momentum values through bullet weight, as velocity cannot make up for it most of the time due to certain constrains."

In the name of mercy, please don't do it!, And what the fu__! What in the He!! are you even talking about?


I'm going to leave this post, been here too long, spent to much time trying to explain why SD is off in the dark. You need to take a deep lung filling breath of air and reevaluate your position on this. Again, this has nothing to do with your friends bullet and what it can or cannot do and/or the reason why. You should become more familiar with Ke(Kinetic energy) along with projectile design. In addition you would benefit by learning just what SD is and how it applies to ballistics. You will learn that it applies more or rather plays a larger role in bullet design and further development. This is just a simple fact and long standing and permanent figure to physics. More of an element to consider in finding a solution. But it doesn't fly.

I hope you can come to peace with this issue and promote your friends bullets (which I'm sure are awesome killers) based on real facts and of course your hands on experience.

Good luck...Cheers....

If you all head one rung up in the Rifle Forums to the Big Bores and read the Terminal Bullet Performance thread you may be enlightened as to why many individuals are discounting sectional density as being supreme in bullet performance. The TBP thread is pushing 139 pages and has stuff scattered throughout relating to traditional C&C, C&C bonded, C&C FMJ, plus monometal bullets ranging from Barnes TTSX through the current CEB BBW #13 FN Solid and HP bullets (monometal brass or copper).

The TBP thread has pretty much demonstrated that SD’s importance arises between two bullets of identical construction and nose profile where one bullet is heavier than the second bullet and even in this comparison SD is way down on the list of importance to the bullet performance. Mix the discussion of SD and bullets of difference construction and nose profiles and the discussion has become a discussion amongst apples, oranges, bananas, grapes, etc.

And yes…there is some .338 caliber bullet testing comprised of a variety of manufactured bullets within the TBP so there is relevance to the Medium Bore Rifles and this Sectional Density thread.

quote:

Dan's chart also contains a 286gr NF bullet that went 30", a Woodleigh 286gr that went 20" and a Norma Oryx 286gr that went 11". What does all this prove? It proves that SD means nothing in the terminal performance big picture.

This is the cardinal stupidity that I am warning about, you just don't seem to get it. Mixing it up - comparing bullets with different constructions and threshold stengths, and then conclude that .... "SD means nothing in the terminal performance big picture."

What a farce. The above is mixing apples with oranges.
Should we not compare rubber bullets with with mono-metal bullets as well?

SD is always at work in a dynamic way.

Just getting back to my statement about the myth of the vapour bubble in flesh.

The notion that a vapour bubble is forming around a supercavitating bullet in flesh is an erroneous assumption. Flesh does not behave like water, and as such we need to make a quantum leap in faith to get to a vapour bubble. The water contained in flesh is housed intra-cellular, in boundary form, and not like water that can flow. Also an animal is not as homogenous as water, it consist of skin, flesh, bone, vacuum, lung tissue, ect. - all very different in density. Once the bullet enters the animal , the so-called bubble needs to be formed, it needs to be maintained, and the bullet needs to be stabilized within that bubble. How is such a bubble to be evoked through the complexity of skin, bone, tendons, muzzle, grass-filled gut, lungs and air and be maintained intact during its journey through an animal? When it comes to flesh and its properties I am much more inclined to believe a medical doctor rather than a physicist. I can well remember that Alf has answered Norbert Hansen very extensively on this issue of the vapour bubble.

I believe FN Solid bullets penetrate better largely due to shoulder stabilization, and not by way of 'supercavitation'. Another dichotomy that I have observed here on AR, is that Norbert placed a steel disc with a sharp edge at the nose of the bullet to form the apparent 'supercavitaion', whereas Michael has shown that slightly deeper penetration is obtained by actually rounding the edges of the meplat, albeit in paper and not in water. But as we all know, paper is not water, and water is not flesh.

SD is tempered or manipulated by the mass distribution around the centre of mass, the nose profile, the meplat, the construction and the bullet material being used. You cannot vary all of these, and then conclude that SD is a non event and absolutely meaningless when different penetration is experienced.

Each to his own - I am done, I had my say, and that is the way it is.

Warrior

Norbert seems to agree with me as least on the importance of SD, and I quote:- (red remarks inserted for humour)

"Sectional density has to do a lot with penetration. (that is interesting to hear) Multiplying with velocity it gives a figure of momentum density, the basic number for all penetration research. To overcome the drawback of the greater length of pure copper bullets, manufacturers recommend the use of lighter bullets, the greater muzzle velocity would compensate for the lower mass. This can accepted for normal hunting conditions, but applied to non-deforming bullets (solids) for dangerous game hunting it can become a disaster. (also interesting to hear) The lower sectional density results in less penetration (see Penetration Index), because less weight normally can not compensated by more muzzle velocity in safe pressure limits. (Oh, our ballistic system favours bullet weight over velocity, one more guy to agree with me, wonderful)

There is another, very important reason to use bullets with a SD greater than 0.3: We don´t know exactly the drag function in animals and it must be very complicated. But one fact is for sure: The heavier bullets are less decelerated than the lighter ones. (another interesting concept to ponder, almost too good to be true) Heavier bullets loose less velocity during their travel through the target. That means: heavier bullets keep their momentum, lighter bullets loose more momentum on their travel through the body. (so much agreement on all these key variables) And keeping momentum results in deeper penetration." ..... Norbert.

Seems quite plausible to me.

Warrior

At the risk of enraging the ire of many on here, I agree with the conclusions listed above by Norbert and warrior. It was what I have seen on elephant and buffalo. I will put up the Woodleigh .458 550 grain bullet against any 480 to 500 grain solid bullet in calibers of .458 or higher when all are launched at 2,150 fps. It will penetrate further than NF, GS, Hornady DGS or CEB #13 of the same weight and velocity.

465H&H

I may be late to the party on this, but I think I understand the crux of the matter. (I emphasize "think" because I'm no expert, just a student.)
Quite a number of hunters, shooters, ballistics students, experts, and "gurus" are firmly in the sectional density camp. The reason for this, I think, is because many conventional bullets traditionally contained/contain lead, which is dense. A similarly sized copper or brass bullet is necessarily lighter because copper is less dense than lead. Therefore I would guess that you cannot easily create a copper/brass bullet of as high a sectional density as a lead-based bullet, without getting into chambering issues.

Now we know there are obviously quite a few hunters, shooters, ballistics students, experts, and "gurus" who are firmly in the sectional density camp and they don't seem willing to budge. They might perceive bullets of lesser sectional density to be "inferior" or not up to the task of taking larger or tougher game. But I think this is in just as much error as thinking that sectional density might not play a role.
If you look at copper itself, you know that one of its properties is strength as compared with lead. Under stress, copper is less likely to deform unless there is a large amount of resisting force. This is not the case with lead, which is rather "soft" despite its greater density and will deform when a lesser force is applied.
So it would seem to me that the effective sectional density of a lead-based bullet would decrease much more rapidly than copper because its penetrating surface area would expand. In addition, lead based bullets are often jacketed and could lose quite a bit of its mass during penetration. That's another factor which would reduce effective sectional density of these bullets.
With copper/brass bullets, this tendency is lessened. Of course, there are expanding copper-based bullets, but these require certain specific designs. Or at least that's the way I've seen it, such as in the case of so-called "Non-Cons". So a copper-based bullet, I think, might conserve a better effective sectional density within a target, as opposed to a "softer" bullet, and would be more effective in terms of penetration.

So do I think the published sectional density figures are often unreliable and are little more than an advertising gimmick. The reality of sectional density is a bit more complicated.

So how's that?

quote:

Originally posted by cobra:

quote:

Originally posted by WhatThe:
There's more BS in this thread than the South end of a north bound herd!

You catch on quick Kemo Sabe.

This is the typical result when Warrior, Gerald, and Alf start posting about trivial issues in anything shooting related. Six pages of.....well....you called it!

SD has never been a trivial matter, but rather a fundementally and inherently reality in ballistics that none of us can wish away - it plays a role in all 3 ballistic spheres in a dynamic way.

The basic reasoning of Glenn is correct, and yes the specific gravity of copper is lighter than lead-core bullets and so is about 12% longer for the same weight, but the problem comes in when people start making inequitable direct comparisons of bullets that are made from different bullet material, construction and shape ..... and how we shoot them meaning which end of the bullet (or its type of nose profile) must spearhead the resistance of air and its in-target behaviour.

Let me illustrate the last scenario where we use a given spitzer mono-metal bullet, let us say the SD=.300 or anything else for that matter, that we shoot in the normal way and then we turn it around, just to consider an extereme condition.

Loaded the 'normal' way, the bullet will encounter less drag in air and be more "unstable" in-target as it is bound to flip over at some distance. Shot in 'back to front' mode, the bulllet will encounter more drag in air and be more 'stable' in-target as it is now in a dart-stabilized position and will result in more reliable straight-line penetration. In target behaviour is now different, but it is the very same bullet with the very same SD.

However, because behaviour is different, we cannot now conclude and make a profound statement that SD plays no role whatsoever. That is plain wrong, as it is NOT an equitable comparison, we have to keep all factors the same, but only vary the weight - as I have done with the Barnes-X bullet that I cut shorter by 6 mm each time to end up with 3 lots of different bullet weights.

As mentioned before, SD can be manipulated for our desired effect, for example by constructing the bullet in such a way that it does not over expand by designing that its expansion gets arrested at some point to avoid shallow penetration, and that weight retention is as high as possible to avoid losing terminal momentum that must drive the bullet despite it larger frontal area. This then increases the effectiveness of the bullet for ensuring that it makes a bigger permanent wound cavity in game for the desired effect, but that is not what we want for elephant hunting, as deeper penetration is our goal, and so we manipulate the SD of the bullet again by changing the material and construction to mono-metal, redesigning the nose profile and meplat, all of which now changes the COG point for more in-target stability.

And that's the way it is.

Warrior

Now I have re read the artivle in the earlier link. I can see clearly now and you guys are over complicating the matter

I have to agree that SD has little to do with penetration, the same goes for energy. Its all about momentum and resistance.

Bullet construction affects resistance, velocity affects both resistance and momentum, bullet mass affects momentum, SD does none of this. Warrior has a lot of good arguments. But one have to understand that you dont need to know or worry about SD, thats just a number with some correlation.

A lighter bullet need more speed to get the same momentum and penetration as a heavier one, but as speed goes up resistance does so also. This can be compensated by adding even more speed or reducing resistance by less expansion/deformation of the bullet.

SD is involved with pentration - here is the math:

Momentum is the driver and the frontal area is the inhibitor of penetration, so ...

Momentum Density = Mo/XSA

and this is equal to = (M x V)/A

and that is equal to = M/A x V

and this is equal to = SD x V

And so SD is part of the equation.

Warrior

quote:

Now I have re read the artivle in the earlier link. I can see clearly now and you guys are over complicating the matter

I see it as several roads to the same city. Just go with whatever makes most sense to you and gives you the least headaches.

But some of us have to analyze it a little further because, well, that's what we have to do. Nevertheless that's a very good article and it's good you got something out of it. A surprising number of people don't even care to take it that far.

We dont need the value for MD either, so SD is not a part of any equation nescessary to find penetration. You might make use of them finding resistance. You'll only ever know SD before impact and after recovering the bullet, when is the right time to pick SD? Is SD and MD an unknown quantity between x and y?

quote:

Originally posted by Warrior:
That is plain wrong, as it is NOT an equitable comparison, we have to keep all factors the same , but only vary the weight - as I have done with the Barnes-X bullet that I cut shorter by 6 mm each time to end up with 3 lots of different bullet weights.
Warrior

You altered velocity and mass and thereby momentum and the relation expansion vs time and distance, which alters resistance and penetration. Distracted by SD.

Sure that is what SD is all about - shooting different bullet weights in a particular cartridge. In my case it was a 108 gr, 142 gr and 175 gr Barnes-X bullet in .284 caliber. That is the decision that the hunter must make which bullet weight he is going to pick, and then if you load the case full, but still within max pressure limits, you will invariably shoot the them at different velocities, and that is the choice that you have to make as a hunter based on your need.

Now the moment you pick a given bullet weight, you have picked implicitly a SD as well. So, no decision can be made without the SD being involved. And as I have indicated the SD is tempered with all the other factors that I have mentioned, SD is not absolute and does not stand on its own, as we operate in velocity windows as to how a bullet will behave:

- Too slow and it won't open up, and likely to tumble in target
- Somewhere in the middle and it opens up say half way, deep penetration likely
- A bit more and we get full expansion as desired, properly dart-stabilized
- Too fast and the bullet loose petals or shatters in a worst case scenario.

All the time Mo/Xsa is dynamically involved together with construction (it integrity ability), and when non deforming solids are involved, its mass distribution around COG become important, as it has no other mechanism to become dart-stabilized as is the case with a controlled expansion bullet.

SD is always involved - in some case we need less and it is not critical as in soft medium game, but then SD becomes progressively more important as we go bigger up to elephant. It is for the hunter to pick his choice of caliber and his SD.

Let us consider the option for elephant hunting as an example and we use BBW #13 bullets in a .458 Lott:

1) a big caliber combined with low-SD bullet (300 grains) and maximize velocity, or
2) a big caliber with a high-SD bullet (500grains) and a low velocity

We load the case full, but within save pressure limits - which one would you go for?
I know of no PH that would opt for option number one.
465H&H has already expressed his choice.

No matter which choice you go for ..... SD is involved.
Not only is SD involved, it will have definite consequences.
At the end of the day the war is between bullet weight and velocity.

Point is, we need to make practical decisions that work better for us.

Warrior

quote:

We dont need the value for MD either, so SD is not a part of any equation nescessary to find penetration. You might make use of them finding resistance.

There's no denying that surface area plays a part in penetration, but in a negative way. In other words, the more surface area the bullet presents in the target, the less it's likely to penetrate. (Assuming a constant momentum.) That's pretty much just common sense. So the resistance that article speaks of *has* to have penetrating surface area as a part of it. Like I said earlier, with deforming bullets that surface area is subject to change very quickly as the bullet expands. This is also obviously the case when the bullet tumbles and/or loses mass.

It's interesting to note that Sir Isaac Newton had an even simpler way to estimate the penetration of a projectile. It's simply the length of the projectile multiplied by a factor called the "specific density." This is nothing more than the density of the projectile divided by the density of the target. Nothing else!

http://en.wikipedia.org/wiki/F...ion_Aproximation.png

Are ya'll sure that you are properly taking Coriolous and rotational forces in to effect?

It also appears to me that oversimplification of the implications of the bell curve distribution are in effect.

SSR

quote:

Originally posted by Cross L:
Are ya'll sure that you are properly taking Coriolous and rotational forces in to effect?

It also appears to me that oversimplification of the implications of the bell curve distribution are in effect.

SSR

I would think that rotational forces would have to do with stability. And that certainly does complicate things!

Ain't nothing nice and neat and easy 'bout this stuff, guys!

SD is involved only because you want it to. The moment you pick a bullet you also pick the manufacturer of that bullet, even if Barnes bullets are known for penetration, the bullet manufacturer is not determining for penetration.

When you say we sometime need more or less SD for different uses, you really say that sometimes we need/accept bullets giving high resistance and quick energy delivery in game, sometimes not. SD has nothing to do with it, its only practical use is to compare similary constructed bullets shot from the same caliber and pressurelevels. Then the higher velocity (low SD) load will penetrate less because the increased velocity also increase resistance. Try out the momentum/resistance view, the principles are a lot simpler when you leave out bullet construction and SD.

When this thread started I was firmly in the SD camp, now I'm not. I think I learned something.

I agree Someoldguy, but as you say, the SD of bullets in a box does little to help us find the expanding bullets surface area somewhere in the target. Resistance covers it.

The co-efficient of drag inside an animal is also not available to the hunter. It is also not a constant through skin, bone, flesh, lung and/or a grass-filled gut.

Mass is known when a box of bullets is bought, and so the SD. It is a conscience decision. Naturally SD is dynamic in target, but through experience we know how a particular bullet behaves most of the time in target. And so our decision is based on SD.

For example in the 30-06 Spr:

150 gr Swift A-Frame, or
165 gr Swift A-Frame, or
180 gr Swift A-Frame, or
200 gr Swift A-Frame,

That is the choice, and its is based on SD up front, no matter the type of brand.
I have just used Swift A- Frame illustratively.

Warrior

465H&H,

quote:

I will put up the Woodleigh .458 550 grain bullet against any 480 to 500 grain solid bullet in calibers of .458 or higher when all are launched at 2,150 fps.

Please explain the logic of comparing the penetration of a 458cal 550gr bullet to the penetration of a 458cal 450gr bullet, if both are launched at 2150fps. I would much rather launch a 450gr FN at 2350 fps and out penetrate a 550gr RN every time.

As far as Warrior is concerned, remember that he does not engage in debate, only repetition of hackneyed phrases learned off by heart, 10 years ago. He answers no questions (he has not learned the answers and possesses no reasoning ability) and presents no theory in context. It would behoove you all to note that one convinced warrior is an army. As he says: "And that's the way it is."

Warrior,
Explain this to me. Why do you think that only you have the right to make SD/penetration comparisons across construction types, but no one else may?

Gerard,

I base my statement on having shot multiple elephant with 550 grain Woodleigh RN solids, 480 grain NF FN solids, Woodleigh Hydro 500 grain FN solids, Trophy Bonded 500 grain FN solids, the Hornady 500 grain DGS and CEB #13 FN solids. All were chronoed at 2,150 fps from my rifles except the Trophy Bonded which was a factory load. It is true that I haven't used any 450 grain .458 FN solids to date but I assume that at the same velocity that they would not penetrate deeper than a comparable 500 grain FN solid of the same diameter.

I have reported these results both here and in articles in African Hunter Magazine but I will summarize again for you assuming that you missed those posts and articles..

On broadside body shots all FN solids and the 550 grain Woodleigh .458 will exit almost always. The 480 and 500 grain RN Woodleighs will almost always remain in the animal with the bullet usually found under the off side skin.

On full frontal head shots of both cow and bull elephant I have found the 480 and 500 grain Woodleigh RN solids penetrate to the first third of the neck, the Hornady DGS to the front of the shoulder bone and the NFFN, Woodleigh Hydro to the loin behind the shoulder. The 550 grain Woodleigh RN solids were found in the stomach contents (sample size 2).

On angled head shots meaning those bullets that enter the side of the head between eye and musth gland and angled toward the off side of the rear of the head, none of the above exited except the 550 grain Woodleigh RN solid. It exited every time for a sample size of 6 for that bullet and shot.

On insurance shots to the top of the head where an exit under the jaw or front of the neck was expected none exited except again the 550 grain Woodleigh RN solid.

These are real world elephant hunting results and not lab tests in artificial media. Remember the above bullets all have SDs of around .300 to .310 except for the .458 500s at .341. The 550 grain Woodleigh .458 has a SD of .375, one of the highest on the market.

465H&H

465H&H,

Just a word of advice, rather make yourself a cup of tea or pour a whiskey, don't waste your time to engage in senseless debate with Gerard Schultz, it is a futile endeavour. He promotes light for caliber bullets and will defend them no matter what - he has done so for the last 10 years that I have known him. Be mindful that he has all the answers and all the reasoning ability and only he knows how to present theory, but 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. Even his observation of supercavitation inside an animal with the naked eye is to his credit or just plain assumption.

This bullet weight and velocity war that I refered to in the end culminates in momentum values in a given caliber within a relatively narrow velocity window, as we cannot stretch it to extremes, as I have explained before. Here we go ...

550 gr @ 2,150 fps = Mo of 168.9 Lbs/Ft-sec
450 gr @ 2,350 fps = Mo of 151.1 Lbs/Ft-sec

So we need the same bullet type for both, and both having the same nose profile with the same meplat - that is equity. As the momentum value of the heavier bullet trupms the lower SD bullet it is clear to see who the winner would be, and that is so because our ballistic system favours bullet weight over velocity.

And let us not forget Gerard's final opinion on SD that is coming through so profoundly and idiotically ... "SD means nothing in the terminal performance big picture." And last but not least, his non-sensical comparisons of bullets with different constructions.

Warrior

Gerard,

I should have added that I really don't have a dog in this fight as I think there has been too much empahsis on penetration. You only need so much to penetrate through the vitals of an elephant. Over penetration in my opinion can cause as much of a problem as too little, especially when hunting in herds. I actually prefer the amount of penetration I get from RN steel jacketed solids in the above calibers. There is enough for any reasonable angled shot while dramaticaly lessening the chance of shooting through an animal and wounding or killing another. All though the 550 grain Woodleigh .458 RN solid has given me the deepest penetration, I no longer use it because of it's unneeded excess penetration.

465H&H

quote:

I agree Someoldguy, but as you say, the SD of bullets in a box does little to help us find the expanding bullets surface area somewhere in the target. Resistance covers it.

The only problem I might see with resistance is that it will vary according to the medium you are shooting into and you'd have to keep coming up with new values for it as you change media.

But, to be fair, I need to look into the momentum/resistance idea a little further and give it a "test drive." I might have been cheering for the wrong team.

465H&H,

In support of your view on penetration here is a commnent or view from Doctari that is quite applicable in our discussion here, and also based on 800+ buffalos:-

Hi Chris,

While important, penetration is not the be all nor end all of a bullet's terminal performance - period. You need enough so that the bullet will get to where intended - but not too much so that it exits and wastes all its energy somewhere else. In my opinion,

No.1 in importance is shot placement. I've made this very clear in my book, 'The Perfect Shot' No animal will survive for more than a few minutes with the top of its heart or the big 'plumbing' which is situated there ruptured, together with its lungs ( which surround that area ) punctured, collapsing and filling with blood.

No. 2 is calibre. There is just no getting away from the fact that 'bigger is better'. This equates to more hitting 'punch', greater hydrostatic shock release and a larger permanent wound channel size. The bigger the hole, the more rapid the onset of the inevitable - period ( provided the hole is in the right place that is )

No. 3 is bullet construction/type/weight/sectional density. Appropriately heavy expanding bullets being the ones of choice for most situations simply because of the better wound channels they create. In this day and age, solids are in reality only needed for elephants and awkward angle 'backing shots'. All the rest can be taken with the 'right' expanding bullets like the Barnes X bullet for buffalo. Lion & leopard are different. They require a more fragile bullet for greater 'shock' release, as to easily 'switch off' the felines highly tuned nervous system

Forth would come penetration, but it must be realized that all these factors are interrelated and must be considered collectively. Penetration is but one piece in the whole confusing puzzle. It serves no purpose in my book to compare different calibre's on penetration alone, especially as all the solids compared will shoot right through a bull buff from the side-on position. Another important factor is 'shootablity' for want of a better word. The 9,3 works so well, because it is 'shooter friendly' as well as being 'adequate' ballistically. This all equates once again to shot placement and we're back where we started !!

Hope this makes some sense to you.

Keep in touch. Kevin Robertson, 03 April 2002 11:42

Warrior

I can't say I understand everything said here. Warrior Listed 4 Swift A frame bullets for the 30-06. Can we assume they will all expand in a simular fashion if the impact velocity is the same? If this is true, which would penetrate the deepest.
I think we can all assume the 200 gr will out penetrate the others. Can this be because of SD?
Someone else talked about 150 gr bullets of different constructions all penetrate differently, duh.
Lets take 3 150 gr bullets. A 270, a 30-06 and an 8 mm Mauser. Let them all be Swift A frames.
The 270 has an SD of 279, the 06 226, the 8 mm 205.
If each of these bullets impact the target at the same velocity they should expand in a simular fashion. Now which one will penetrate farther. My guess is the 270 with the highest SD. What do you folks think?
When you get as many of the circumstances to match, impact velocity, bullet construction. The factor that effects penetration is SD. Am I correct in this assumption?

465H&H,

quote:

I base my statement on having shot multiple elephant with 550 grain Woodleigh RN solids, 480 grain NF FN solids, Woodleigh Hydro 500 grain FN solids, Trophy Bonded 500 grain FN solids, the Hornady 500 grain DGS and CEB #13 FN solids. All were chronoed at 2,150 fps from my rifles

quote:

Please explain the logic of comparing the penetration of a 458cal 550gr bullet to the penetration of a 458cal 450gr bullet, if both are launched at 2150fps. I would much rather launch a 450gr FN at 2350 fps and out penetrate a 550gr RN every time.

In case you do not realise it, a 450gr FN, at the higher speed, is more likely to track straight than what a RN is likely to do, and it will leave a larger diameter and volume wound channel while doing so.

quote:

Warrior,
Explain this to me. Why do you think that only you have the right to make SD/penetration comparisons across construction types, but no one else may?

I notice from Kevin's letter of 2002 that you quoted above: "You need enough so that the bullet will get to where intended - but not too much so that it exits and wastes all its energy somewhere else." He also mentions "greater hydrostatic shock release" and clearly believes that hydrostatic shock is the correct term and reality.

Elsewhere he has mentioned that he believes that there are negative aspects to bullets that are "over stabilised". He believes that a faster rate of twist induces more yaw and that the Taylor Knock Out Value tables are true. He calculates static stability with the Greenhill formula.

He has written gems such as:

"Consequently, the total energy force (i.e. the forward and centrifugal forces) that a fired bullet experiences, is the product of both these energy values in other words, its muzzle energy (ME) times its rotational energy (RE)."

"the dimensions of the permanent wound channel are directly proportional to a bullet’s final expanded diameter cubed."

This puts a definite perspective on his ballistic opinions and it becomes clear where much of your crackpot ideas are generated, not so?

Kevin was in our factory on occasion. I asked him whether a bullet, such as the heavy 375 softs he recommends, which is incapable of an exit wound on a broadside shot, can be used to take a straight going away shot. I am still owed an answer.

You also do not give answers when you are cornered and when a truthful answer will show an opposing view to be true. What say you to my questions Chris? Got any answers or only childish insults that prove you do not read replies?

quote:

And let us not forget Gerard's final opinion on SD that is coming through so profoundly and idiotically ... "SD means nothing in the terminal performance big picture."

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 are firmly in the second, doing your best to mislead the third.

Have you had a look at Jim's signature line? Fits you like a glove.

44magLeo

The 200 grain Swift will outpenetrate the others because of higher momentum all things else beeing equal.

The 270 bullet will outpenetrate the others since it has the same momentum but the smaller diameter give less surface area and resistance in game.

The bullet with highest SD when velocity, bullet construction, caliber is equal has more mass and higher momentum. The higher momentum give more penetration when resistance (expansion characteristics) is the same.