Mark H,

Essentially I have no disagreement with what you say. The mechanism of the bullet genre that you refer to is indeed different, and as such penetration in-target differs by virtue of all the differences between the expanding bullet that keeps its petals (at say 100%) vis-a-vis the bullet that loses is front portion to become essentially a flat nosed cylinder with reduced terminal momentum.

What worries me a bit is the notion of the "drastic increase" in velocity that seems to be propagated. How much is this really for the same weight of bullet? It would certainly be an orange and apple comparison if we compare a 180 gr Barnes-X with a 130 gr GS-HV bullet.

Back to the SD question, and in particular the statement that Gerard came up with. On the one hand it was plausible to argue that SD is irrellevant, but now this very same brigade hauls SD in to say its main role is to cause greater expansion. My submission is that it is being used out of context. Alf stated so as well. Let me give more examples.

1. If the drilled hole of the Barnes-X bullet is made say another 3 mm's deeper, the petals will peel further back. Likewise if they are drilled shallower, the mushroom will become smaller. So design is key here. Swift A-Frame moved their "partition" further forward in comparison with the Nosler partition bullet and they opt for a bonded front core. All for very good reasons. To maintain a higher weight retention ratio and to arrest expansion earlier. All bullet construction issues, nothing to do with SD.

2. The other thing is that it is velocity dependant - too low a velocity and the bullet will not open or only partially, with adequate velocity we will see full expansion of petals, too much velocity and petals will either over-expand or shear off. Sure momentum is at work as the driving force, but momentum is velcity dependant.

Thanks for your comments.
Warrior

quote:

Originally posted by gumboot458:
..........I think MarkH is right,,, but bullet CONSTRUCTION is Key.,.,.,.,.,.,:

exactly

quote:

Originally posted by jeffeosso:
The Berry-Smith SD formula modification:

For monometal, brass or copper, the threshold value for appropriate SD may be reduced up to and including .025 to compare with conventional bullets. Alegorical evidence of bullets of this construction "penciling" (acting as solids) confirms this supposition.

Chris,
You claim Alf said:

quote:

Therefore if we shoot two expanding projectiles of equal construction ( thus similar yield strength) one heavy and one light, both at equal impact velocity, both will be subjected to the same tip force and thus will expand equally.

When did Alf say this? I see you have fixed some of your mistakes above. Notably, you changed a previous post, after you were called a moron in an effort to save face. Typical.

From Bullet Penetration (MacPherson) page 142: "Effect of Sectional Density. An increase in initial (undeformed) bullet sectional density will cause equivalent expansion at lower velocity. Greater expansion occurs at the same velocity because the decelerating forces must act for a larger time interval to reduce the bullet velocity." Page 143: "A very crude analysis shows that a 20% increase in sectional density would lower the velocity for equivalent expansion by about 5%."

Yes, "MacPherson." Thank you Gerard.

quote:

Originally posted by RIP:
Alf, I understand how exasperating Warrior's last post was to you. Do not let it drive you away. He needs more help. As Rob said, the bullshit is rolling along.

RIP,

With all due respect, I think you are mistaken. Alf is exasperated because he tried to explain to us with seemingly great difficulty that:

1. SD is involved in the whole process of the ballistic event; that it is not irrelevant; and that it cannot be replaced or made up by velocity. This has been continually challenged, basically up to yesterday.

2. That the expansion of the bullet tip is governed by other factors (as mentioned in detail) and not SD.

So perhaps you should see Alf's comment in this light, and not be so quick to blame it on me. Remember we are here to learn from each other. I will appreciate any constructive contribution that you can make in this regard of deciding that CONSTRUCTION of the bullet or the SD of the bullet is the determining factor as how the tip of the bullet will expand.

Thanking you.
Warrior

Warrior

Gerard,

I was called a moron because Ratmotor pointed out that the bullets must be shot at the very same velocity and not at differing velocity, as IF it would change the outcome of the Barnes-X bullet. I have not changed my stance on this issue. In order to address this non-event in my opinion, I proposed that we shoot Swift A-Frame bullets in a 30-06 Spr as follows:

a) Shoot a 150 gr bullet at say 2,500 fps
b) Shoot a 180 gr bullet at say 2,500 fps
b) Shoot a 200 gr bullet at say 2,500 fps

Then we can see how valid your statement is that you made.
Construction and design of the bullet in this regard is FAR more important than SD.
If this makes me a moron, then I will wear the title with honour.
But may be, just may be, more morons are lurking around the corner.
Or may be that you have known all the ballistic answers well before your birth.
Thus no need to learn things the hard way like some of us poor mortals.

Warrior

Warrior,
Alf was mistaken too in not admitting that the heavier bullet will expand more when fired at the same velocity, all other bullet factors being equal, and assuming the twist rate is sufficient to stabilize both the light and heavy bullet. There is the "T" word too.

This is counting angels dancing on a pinhead, but fire your three Swift bullets into water at 1600 fps and see which one expands the most.
I am sure it will be the heaviest one, if they expand at all.

At 2500 fps impact with water, all three Swifts may be expanded down to the partition, or not, I do not know.
The heaviest one will have the greatest chance of doing so, and possibly going even farther to bulge the base of the bullet, the way Swifts do.

quote:

This is counting angels dancing on a pinhead, but fire your three Swift bullets into water at 1600 fps and see which one expands the most. I am sure it will be the heaviest one, if they expand at all.

RIP,

I think the 2 conditions you describe are mutually exclusive and cannot support your argument. As I have explained before, expansion is velocity dependant to varing degrees ... ie under-expansion, ideal expansion and over-expansion with enough abuse. Construction of a bullet is based on design criteria to operate in a "green band" where it will perform as intended. For some bullets this green band is very narrow and for some others, much wider.

If we really go into what MacPherson meant, we will see that it was used in terms of normal old fashioned conventional bullets that do not arrest expansion by design. Unlike as to what we see in the Barnes-X and Swift A-Frame bullets, that overule the normal behaviour of conventional bullets. Sure greater momentum (not SD) would mean a greater push forward that would act on the bullet. That is understood, but what we need to recognize as well, is how by clever design we can change the outcome, just by taking it to an extreme and make a non deforming Solid !!!

Warrior

Yep, he is hopeless.
My condolences to all affected parties.
I'll just watch, for now.

Gerard,
Talk to me about the .395 sometime, please.

RIP & Gerard,

Just as a parting shot ... Projectile deformation, as seen in the tip of the bullet (ie the mushroom) is dependent on two entities:

Tip force ( F) and time of impact (Ti)

In rough approximated form, the formula reads:

Linear Momentum I = F x Ti

We can now substitute: I = m x v

thus m x v / F = Ti

So that in theory, if we take two projectiles of equal construction, keep V equal, and only change M, then the heavier bullet (ie higher SD) will have a longer "impact time". Thus if both bullets come to a stop in target, then the heavier bullet is going to penetrate deeper.

But we say both bullets expand, thus the reference area (A) changes. If both bullets expand equally, as determined by the design (say a Barnes-X), and the bullets are shot within the velocity window where we usually use them, then surface area A expands to it's limit, and now the heavier bullet still has a greater Impact Ti, where Ti = m x v / F.

This gives credence to my view on "velocity windows" and why they are important. If V is below the window, the values of A may differ between our two bullets, and then penetration time Ti , becomes a function of how big A gets.

Warrior

Two expanding bullets of the same construction, but one heavier than the other, fired at the same speeds, will result in the heavier bullet expanding more. If the speeds are high enough for good expansion on both, the heavier bullet will penetrate less.

No more and no less was said, but you are arguing against the obvious with all sorts of red herrings. I said same speed and same construction because those factors also influence expansion and we all know that.

So, in your argument (for the sake of argument):

You vary the speed while I said same speed.

You vary the construction while I said same construction.

You say that construction determines expansion. You are wrong - It influences expansion but we all know this.

You show an out of focus sample where the speed, weight and construction varies. That is weird. How does that prove anything?

You repeat your A-Frame post (which you conveniently inserted, after the fact, above the moron post) and throw down a challenge:

quote:

a) Shoot a 150 gr bullet at say 2,500 fps
b) Shoot a 180 gr bullet at say 2,500 fps
b) Shoot a 200 gr bullet at say 2,500 fps
By "definition" we should now see progressive increase in diameter expansion, right?

You thought this has not been done, but it has. This is not my work and the website is copyright, so I wont steal the pictures as you are so fond of doing, but you can read the results and weep.

Pictures of bonded core, solid shank, grooved bullets, expanded at different impact speeds:

270 cal 130gr and 150gr with the same nose construction.
At 2000fps, the mushroom on the 150gr bullet is visibly wider than the 130gr bullet.
At 2200fps, the mushroom on the 150gr bullet has reached the shaft and 130gr bullet only gets there at 2400fps.

284 cal 140 and 160gr with the same nose construction.
The first picture of the 140gr bullet is at 2400fps impact. Some of the shaft is still visible.
The 2400fps picture of the 160gr bullet shows the mushroom completely covering the shaft.

308 cal 180gr and 200gr dimensionally similar but the 200 is of heavier construction.
At 1800fps, the 180 shows a larger mushroom. This is expected as it is of lighter construction.
At 2000fps, the 200 has the larger mushroom at the same distance from the shaft as the 180. Again expected.
At 2200fps, it is a no contest as the 200 mushroom is bigger and closer to the shaft.

.358 cal 200gr and 250gr.
At 1800fps, the 250gr bullet mushroom is much bigger and closer to the shaft than the 200.
At 2000fps, the same condition is seen.

.375 cal 250gr and 300gr with the 300 of heavier construction.
At 1800fps, they are virtually identical, despite the heavier construction of the 300gr bullet.
At 2000fps, the 300gr bullet has a larger mushroom and has opened further towards the shaft.

.458 cal 350gr and 400gr of similar construction and 450gr of similar dimensions but heavier construction.
At 1700 fps, the the 400gr bullet has the mushroom further towards the shaft than the 350gr bullet at 1750.
At 1900fps, the 400gr bullet mushroom is identical to the 350gr bullet at 2000fps.
At 1700fps as well as at 1900fps, the 450gr bullet mushrooms further towards the shaft than 350 or the 400.

Exactly as expected, in these examples, the expansion of the expanding portion of the bullet is driven by the amount of weight behind it. When the expansion is arrested by the construction of the bullet, instead of further radial expansion, the shaft starts compressing and this is again driven by the same factors as the expanding nose portion.

Now please tell me:

1. You claim Alf said:

quote:
Therefore if we shoot two expanding projectiles of equal construction ( thus similar yield strength) one heavy and one light, both at equal impact velocity, both will be subjected to the same tip force and thus will expand equally.

When did Alf say this?

2. Are you saying that MacPherson is wrong?

3. Are the pictures that back up the above descriptions all fake?

4.

quote:

Sure momentum is at work as the driving force, but momentum is velcity dependant.

You agree that expansion is driven by construction and speed but, for some reason deny that weight influences expansion. In the face of what MacPherson says and the evidence of the above bullets, you continue your worthless argument. Why?

In your "parting Shot" above you actually prove why MacPherson is right and, therefore my statement as well, when you say:

quote:

Tip force ( F) and time of impact (Ti)

Yet you can't see it.

You are a sick puppy.

quote:

Originally posted by Gerard:
100% weight retention is nice to have, if the caliber/bullet combination is incapable of going faster than about 2400fps. At that speed and lower, the higher the retention, the better, I would say. However, with caliber/bullet combinations capable of more speed, there is a better way. It also involves gross transgression and bending of "Sd Laws".

A good example is professional hunter and outfitter, Jacques Greeff. He used a 450 Rigby to shoot seven Black Wildebeest recently. BW have similar live weight to that of the lioness mentioned in my previous post. The bullet Jacques used was a 315gr HV at 2900fps. Even on lengthwise shots and quartering shots, not a single bullet was recovered. At 2900fps, these bullets will lose the petals some way into the animal and, up to that point, cause about the same amount of damage, at similar penetration depths as a bullet that gives full retention. The advantage is that the lighter, faster bullet will then lose the petals and continue on, much deeper than the slower bullet, and usually punch through. Total wound channel volume exceeds that of the slower bullet and that can only be good.

Witness the fact that the recovered (mono) bullets we see, usually show excellent retention. The ones that punch through and produce bang flops with more certainty than the ones that are retained in the animal, are the ones that have morphed through the reduction in Sd, with a mushroom, back to an increase in Sd, when the petals part company. The ones you never see actually work better, despite the fact that the tradition of complete retention has been grossly violated.

Needless to say, none of this applies to lead core bullets.

..............Thank you sir .I should revive my Brown bears arn,t Elephants thread on the Alaska forum if I could figure out how to transfer your post .......That is what Master Guide Andy Runyon [deceased] said when the 416 remington first came out .... Lighter weight bullets going Real fast !!! complete penatration with tennis ball - bowling ball size exit wounds ,,, and a flatter trajectory .....Thank you Gerard.......Now the next test , if it hasn,t already been done is Cape Buffalo , but also Hippo ,Water Buffalo and Elephant ....How big a bullet needed ,,,going how fast ....And will a fist size exit wound cause , Bang Flops ,Say a 400 gr GSHV in .505 or ,510 dia @ 2900 fps.. The Gibbs should be able to produce that ...Probably the Jeffries also ...???????

...............Or , what about a 600 OK with a 525 gr GSHV @ 2900 fps Since the 600 NE with solids does not appear to Bang Flop cape buffalo @ normal velocities ,, would the 600 OK ...What about the 577 T Rex with a 500 gr @ 2900 fps ??????????????

Gerard,

I have just skipped your ramblings and twisting of events, as it is just senseless to mull over them.

With your approval of the math given, it seems then that we have actually agreed with each other all along, even though we use very different words and approach it from different angles ... that is a miracle !!!

You just need to change your website now, and remove the comment that SD is not some ballistician's macabere sense of humour and that it is a practical joke, not so? Replace it with the words that SD features in the total ballistic event and that it even works for your bullets. Ridiculing SD should not be the focus, but rather to put it in its proper context.


Warrior

Hey Warrior,

quote:

Gerard,
I have just skipped your ramblings and twisting of events, as it is just senseless to mull over them.

Translation: Duh.....I dont understand......dont want to be confused with facts.......duh......what happened?

I think we have just witnessed a five way Cluster F---K of near biblical proportions!. A truly Magnificent acheivement I might add. Congrats. !-Rob

Let me see... what have I learned that is relevant in reading this post........... Why don't you’ll print out all your theories and send them to me, that way I can read and digest them more thouraley. I also need some paper to start the fireplace.
I will just keep buying quality bullets and shooting them.
Bill

quote:

I have not read such a load of nonsense in years. Thanks, it brought a great deal of laughter to an otherwise boring day. -Rob

Hi Rob,

I noted your remark about us grappling with this problem to get to a better and more complete understanding of the significance or irrelevance of SD. I would appreciate it if you could tell us your understanding, as it seems you have some info that could be useful.

Perhaps you could also give us your view on the findings of Karl Sellier that published in his book Shusswaffen und Shusswerkungen, Second edition in 1982. His tests on the effect of increasing velocity in lieu of mass in non deforming stable projectiles dealt with the issue of SD and penetration. The conclusion was that an increase in SD leads to less energy transfer to target per unit distance penetrated and so contributed to deeper penetration. I think we still have some controversy on this topic as you have noticed.

Sharing of information is what makes us strong and able. It is not fair to sit and laugh at us when we go off the road.

Thanks
Warrior

Solids:
Certainly the Higher SD FN SOLID NONDEFORMING bullet, as long as it is stable, will penetrate better and leave less energy in the animal with an exit ... than would a lower SD that stops in the animal due to its lower momentum and tumbling at the end of its path in animal ... assuming both bullets impacted at same velocity ... but the lower SD bullet can be more stable than the higher SD one and it can be driven at a higher velocity ... so it is probably going to be transiting through the animal and out the other side, at higher velocity ... so either way it looks like the lower SD bullet is going to deliver more energy to the animal, whether pass through or stopping in the animal, unless the Higher SD FN stops in the animal. Then the opposite is true.

Softs: A different situation than solids.
Certainly a Higher SD EXPANDING SOFT bullet will expand more than the lower SD bullet of same construction at same velocity. The Higher SD bullet will certainly dump more energy into the animal than the low SD bullet at the same velocity, whether they both exit or not.

Where is the controversy?

Chris,
You ask Rob:

quote:

Perhaps you could also give us your view on the findings of Karl Sellier that published in his book Shusswaffen und Shusswerkungen, Second edition in 1982. His tests on the effect of increasing velocity in lieu of mass in non deforming stable projectiles dealt with the issue of SD and penetration. The conclusion was that an increase in SD leads to less energy transfer to target per unit distance penetrated and so contributed to deeper penetration.

As you have obviously not read the book yourself, and what you say above was copied from Alf's post, why not just copy and paste the rest of it as well? Don't bother, here it is:

quote:

In 1982 Karl Sellier published in his book Shusswaffen und Shusswerkungen, Second edition: his tests on the effect of increasing velocity in lieu of mass in non deforming stable projectiles specifically with regards to the issue of SD and penetration.

They also validated this by means of experimentation and a valid mathematical derivation that would explain at the hand of energy transfer to target what happens when you speed the projectile up by trimming weight as Gerard suggests with his FN bullets.

The results of the tests show the following:

1. An increase in SD leads to less energy transfer to target per unit distance pnetrated and thus deeper penetration. The lower the SD the shallower the penetration, the bigger the energy dump to target and the bigger the TC

2. As temporary cavitation is energy transfer dependent it means that the more energy is dumped the bigger the TC, the less energy is dumped the smaller the TC.

3. Velocity Limits are reached where drag becomes so high that the drag force exceeds the yield strength of the projectile material and the projectile deforms and or fragments. This leads to even larger energy transfer and shallower penetration, but large TC's. The relationship to drag and velocity being that the drag value is equated to the velocity squared.

For their tests the velocity limit was 2800 m/s for steel projectiles, at this velocity the projectiles deformed and fragmented. That is roughly 9186 fps Roll Eyes
( tensile strength 780 N/square mm)

Charters and Charters in Journal of trauma 1976 found exactly the same results with their testing.

At 2850 m/s velocity the charters's steel projectiles also deformed and fragmented with a dramatic increase in TC but equally dramatic loss of penetration depth. Charters fired their projectiles to speeds of 5510 m/s = 18000 fps

Typically, you only quote the first bit that suits your narrow point of view. If you read the entire quote, it makes a pretty good case for lighter and faster bullets that are designed to take advantage of the findings, even though the study (1982) predates the modern turned bullet.

You highlight the fact that you do not have an original hair on your head and you will pick a scrap with anybody, for the sake of arguing. If you try and bait Rob, you will come short.

Gerard,

Gerard our discussion here is not about temporary cavitation (TC), it is about SD and penetration, if you read the very first post in this thread. So I quoted the relevant portion.

By the way, are you going to amend your article on your website and give SD its proper recognition?

I am interested to hear Rob's opinion and not to pick a scrap that you are so fond of doing and to make personal attacks. You can hardly make a post without being derogatory.

The forum exist to hear other people's opinions too Gerard, and you may have noticed that I invited him and not you.

Warrior

Warrior- let me give you some sage advice. Stop Googling. Pse stop quoting papers you can't understand and make up conclusions that are unsubstantiable. You are way out of your league. From what I've read you and your buddies would have flunked my and probably any other physics 101 class and frankly it would be embarassing if it wasn't so funny Cause you sure as hell can't be serious. Enough said. pay attention though, not everybody here is stupid.
It has made for a real good laugh though and thanks for that. I truly assume youy guys were just having fun. -Rob

Rob,
Good job on Bozo!

Yes! Having a lot of fun here!

........O K ,.,., so How about my query ...,.,or are bovines impervious to big fast bullets .....It seems like the guy with the best Yankee ingenuity as far as expanding bullets are concerned is a South African ..

RIP- They breed fast! Hard to keep up! Medium calibers are ineffective, and you for sure have to avoid head shots as they are ineffective. The brain is located to far south to have any effect. I just love the Googlers though. Hysterical new level of Bullshit has evolved lately. I know they are not serious, so I just sit back and enjoy! Looking foreward to the next episode of Dumb and Dumber!
As my old engineering prof said( at MIT), better to keep your mouth shut and have people think your a moron, then to open it and AND REMOVE all doubt. ENOUGH SAID!-Rob

gumboot458,
Big bovines succumb to big fast bullets exceptionally well, if some common sense is applied. With turned mono bullets, that do not deform (solids), or are designed to deform in a certain progression (expanding GSC HV or HP), the faster they are driven, the better the effect. It is better to reduce the weight a notch or two and gain gyroscopic stability and speed and take advantage of the way the bullet is designed to work.

The rule of thumb is to follow the manufacturers recommendation for a specific caliber. Any bullet, regardless of how it is made, can be applied outside of its design parameters. I like bullets that have as wide a design parameter as possible. RIPs test with the new .395 HV showed that it can be applied from impacts as low as 1600fps, all the way up to beyond 2700fps. We know it will be good to at least 3500fps. I would like to see how many bullets will expand to close to double calber at 1600fps, retain better than 75% weight when pushed beyond impacts at 3000fps and still maintain a bone crunching straight path through the animal.

It simplifies matters when you do not have to worry about the integrity of the bullet, but can concentrate on the job at hand.

Chris/Warrior/Truvelloshooter,
Why should I amend the article on Sd on our website? You obviously did not read it yourself. The article deals comprehensively with the definition of SD, misconceptions around Sd, how varying bullet construction influences Sd, the role of Sd in external ballistics, the role of Sd in terminal ballistics, the mythical Sd of .3, how Sd changes when the bullet impacts a target and deforms or does not deform, and the fact that it cannot stand alone as a measure of how a bullet is likely to perform.

What more could you want in an article about Sd? In fact, what is in that article that is incorrect technically or not absolutely true? What do you disagree with? I have to ask even though I do not expect you to answer, as you have evaded this question before. It is interesting how you evade the questions when you are cornered.

A thought: Maybe you misunderstand my Sd article because it is somewhat tongue in cheeck. We have seen that this goes way over your head at times (Sexual destiny ring a bell?)

Sectional Density - A Practical Joke?

Your concluding paragraph basically ridicules the importance of SD ...

"This leaves only one question unanswered. Who first came up with the theory of sectional density? Was it some ballistician with a macabre sense of humour? Did he put forward this theory as a joke and it got out of control? Sectional density seems to be the ballistic equivalent of an internet chain letter. No matter how illogical or outdated or disproved it is, it keeps on popping up. Almost like the concept of hydrostatic shock, but that is another story."

There is no need to denigrate SD in order to sell bullets that are light for caliber. That is the whole drift of the article. The focus can just be monometal bullets can afford to be lighter by virtue of their strength and construction and how they perform. SD works for your bullets as well. Bullet behavior is the other important focus area in-target.

Heavier bullets (higher SD bullets) do have their use and application, and that is why we cannot make blanket statements like it is irrelevant or coincidental, etc.

Warrior

quote:

Your concluding paragraph basically ridicules the importance of SD ...

I see. The tongue in cheeck tone of the entire article escaped you. There is nothing new about that, there is so much that you miss. Am I right in assuming that you find no technical fault with the article. No lies, mistakes or wrong facts that could lead a newby down the wrong road? Your only problem is that you think:

quote:

There is no need to denigrate SD in order to sell bullets that are light for caliber. That is the whole drift of the article.

Now how did you get to that assumption? You sure have to dig deep for that one. Any imaginary reason is a good one for an argument, hey?

Tell you what. Check out this article and see if you can also make an argument that it is written to sell GSC bullets.

quote:

Heavier bullets (higher SD bullets) do have their use and application,

Absolutely, and that is why we make those as well, but we make heavy bullets for other reasons. The higher Sd number is irrelevant, a coincidence.

quote:

and that is why we cannot make blanket statements like it is irrelevant or coincidental, etc.

Ah, but I can and just did, especially when you come along and say Sd is a likely indicator of the way a bullet will perform terminally.

quote:

Originally posted by MarkH:


155gn 0.375 @ 3300ft/s

Mark

Gerard,

If I have to go buffalo hunting and choose between a .375/155 gr bullet like above and your .375/265 gr HV bullet I would pick your bullet, ie the heavier/high-SD bullet. You can evalute this comparison any way you want, the heavier bullet will be the one of choice in this caliber (375 H&H).

When I pick a heavier bullet over a lighter bullet, I effectively discriminate against the lighter bullet for a valid reason. If SD is supposedly irrelevant, then I should be indifferent as to the choice, as I can make up for the lower SD with velocity. But the fact that you make heavier bullets as well, is proof that SD is relevant. Hunters dicriminate daily when they pick one bullet weight over the other, whichever brand they prefer.

And this is why Alf made a similar posting in this regard ... "I just need to clarify something for the speed over mass freaks . In 1982 Karl Sellier published in his book Shusswaffen und Shusswerkungen, Second edition: his tests on the effect of increasing velocity in lieu of mass in non deforming stable projectiles specifically with regards to the issue of SD and penetration. They also validated this by means of experimentation and a valid mathematical derivation that would explain at the hand of energy transfer to target what happens when you speed the projectile up by trimming weight as Gerard suggests with his FN bullets."

The tongue in cheeck tone is pure crap - just another spin on things, as always.

Warrior

quote:

Originally posted by Doug Turnbull:
HOw did the SD of .300 become the "#"?
Why dont' they take into consideration the constuction of the bullet wiether lead or mono.
I have shot 500 grain bullets that are better SD than a 450 yet the 450 out penatrates the 500.

One certainly must consider bullet construction! My guess is that we are stuck on an S.D. number around +- 300 because, early in the 20th Century, African hunters who were beginning to acquire experience with the smaller caliber (ie, under 12-bore) rifles used on dangerous game, (especially those of .45 or smaller) came to the conclusion that "solids" in the vicinity of 4 calibers in length, if properly shaped and stabilized, gave optimum penetration on heavy game. This works out to an S.D. of 300, or somewhat more.

quote:

One certainly must consider bullet construction!

For sure !!!

In the .458 Superpenetrator Solid, it has been shown that one can vary the depth of penetration purely by varing the the flat meplat, eg from say 9mm to 7mm. That has to do with the fact that the same amount of momentum is being applied over a smaller cross sectional area and hence deeper penetration.

If bullet weight is different, than we have to ask what were the velocities when the 2 bullets were shot, so we could see what the momentum differences were. In other words one load could have been a hotter load than the other, and so forth.

If construction and design differed, then it just opens a hornet's nest.

Warrior

All bullets of the same weight for a specific caliber diameter have EXACTLY the same Sectional Density. SD=Weight/(Diameter Squared)

Bullets of the same weight and caliber diameter but of different design absolutely do have different Ballistic Coefficients. This is because bullets of different design have different form factors. BCs are commonly estimated with the form factor method.
BC=(Sectional Density)/(form factor)

The Ballistic Coefficient is a measure of how efficiently the projectile penetrates air.

If you cannot use Sectional Density alone to predict how well a projectile will penetrate air, trying to use it alone to predict how it will penetrate anything else is equally futile.

Warrior

Since you brought me back into this discussion it is quite possible and has been proved that you can kill Buff with a 155 gn copper bullet. Here is the bullet

However if I were specifically going after buff yes I would probably use the GS 265 bullet. If predominantly large plains game the KJG 155.
The original question was not species specific so here are the guidelines as I see it.
Std lead/copper >= 0.3 SD
Premium lead copper = 0.3 SD
Dangerous game copper = 0.275 SD
Large but not dangerous game copper 0.1.5 - 2.5 SD

I have used 175 gn lead copper bullets in 7mm that folded up and failed to pass through a wild boar, so in answer to the original question modern bullet construction is the factor that determins the required optimum sectional density and not the other way round.

Mark

Mark,

Well put, I agree with you. Thin-skinned game does not require heavy bullets with a high SD number; they can be taken with with relatively small bore bullets, not weighing more than 140 grains with a fairly low SD. To site an example, one can take with a 140 gr Barnes TSX bullet game up to kudu and eland with well placed shots. The SD translating here is just .248, coming in just under your spec of .250.

Your spec underscores my point that SD is alive and kicking.

And modern bullet construction can arrest expansion at some point.

Warrior

Hey Warrior,
Would you use a 175gr Barnes bullet loaded to 1300fps for kudu at 100m with your 7x57 or would you use a 140gr Barnes loaded to 2600fps? (1300fps is not a typing error). Motivate your choice using the SD as reason please.

As I said on a previous post Barnes are a bit of a hybrid bullet.
A 175gn copper bullet in 7mm is fine in lead/cooper but a poor use of design/materials in copper. THey cannopt go @ anything more than moderate velocity without developing some seroiusly high breach pressures.They keep to the traditional bullet/caliber weights and consequently SD because the average hunter cannot understand that low SD very high velocity monolithic bullets work equally well and therefore their sales would plummet.
I get constantly asked by people that they like what they see with the copper banded bullets say in 30 cal but would like then in 180 gn
Possibly a better way to put is that banded monolithic bullets should not exceed a SD of .275 for those who need rules rather than guidelines

Chris/Warrior/Truvelloshooter,
You quote Alf as saying:

quote:

In 1982 Karl Sellier published in his book Schusswaffen und Schusswirkungen, Second edition: his tests on the effect of increasing velocity in lieu of mass in non deforming stable projectiles specifically with regards to the issue of SD and penetration. They also validated this by means of experimentation and a valid mathematical derivation that would explain at the hand of energy transfer to target what happens when you speed the projectile up by trimming weight as Gerard suggests with his FN bullets."

Is this supposed to be contrary to the lighter faster viewpoint? If you think it is, you are making a mistake. This proves two things: You only read as far as you think you need, to "prove" your narrow point of view and, secondly, with the addition of the next paragraph, the two paragraphs are actually in favour of lighter faster bullets. I do not expect you to grasp the context of the following and you will probably revert to the old saw that I twist things, but here it is anyway:

quote:

The results of the tests show the following:

1. An increase in SD leads to less energy transfer to target per unit distance pnetrated and thus deeper penetration. The lower the SD the shallower the penetration, the bigger the energy dump to target and the bigger the TC

In the event where the lower Sd bullet has enough penetration to shoot through the vital area of the animal and/or exit the far side of the animal, the shallower penetration, relative to that of the higher Sd bullet, is of no concern because there is enough of it. It is hoever an advantage of the lower Sd bullet that it causes a larger temporary cavity, because that will contribute to the wound channel size, especially if the deformed bullet is cylinder shaped or concave in shape and not a rounded shape.

In real life of course, more high Sd bullets are recovered with high weight retention than bullets that have shed the petals and shot through. This supports two theories very well: 1. Slow, high Sd bullets expand with too little force available to tear off the petals, increasing the force that retards the bullet and thus reduces penetration. 2. If a fast, lower Sd bullet expands reliably from low impact speeds, sheds the petals and then the shaft remains intact, penetration far exceeds that of the higher Sd bullet and total wound cavity volume is larger as well.

The theory behind this was in the remainder of Alf's post, which you also forgot to read and copy and paste, so here it is:

quote:

2. As temporary cavitation is energy transfer dependent it means that the more energy is dumped the bigger the TC, the less energy is dumped the smaller the TC.

3. Velocity Limits are reached where drag becomes so high that the drag force exceeds the yield strength of the projectile material and the projectile deforms and or fragments. This leads to even larger energy transfer and shallower penetration, but large TC's. The relationship to drag and velocity being that the drag value is equated to the velocity squared.

A reminder: Don't harp on the "shallower penetration". As I pointed out above, even this "shallower penetration" is sufficient to get the bullet through the target. That is why manufacturers make caliber / bullet specific recommendations that you tend to not understand/follow.

In English, all this just means that properly constructed faster and lighter bullets poke bigger holes in animals and to a greater depth. Now that is as good as it gets.

PS. Please correct spelling of names and titles when you copy and paste. We are not all authors of note but it grates when the same names and titles are misspelled over and over. It goes to a lack of attention to detail and it is a basic courtesy to spell these things correctly, especially if you claim to be published.

quote:

Originally posted by Gerard:

A reminder: Don't harp on the "shallower penetration".

This is good advice. Yes, lighter projectiles when fired at the same velocity as heavier ones will penetrate less. Using Newton's equations this is academic. The lighter projectile has less momentum and less energy under these conditions so the conclusion is pretty obvious before you even start crunching numbers.

The truth is unless you are specifically pursuing reduced power loads for the lighter projectile, launching it at the same speed as the heavier one isn't going to happen. The lighter projectile is gonna be faster every time.

If you increase the speed of the lighter projectile enough to achieve equal Momentum for both light and heavy projectiles, Newton's equations show you a very different result. The lighter projectile absolutely has more energy. The force the projectile must overcome to penetrate a given distance goes up with the square of it's velocity. By maintaining momentum, the force the projectile can utilize to penetrate the same distance is also increased by the square of the velocity.

In short, properly designed the lighter projectile can achieve the same penetration distance as the heavier one if the momentums are the same.

And this goes way back to the original point Doug Turnbull made in this thread. Noting his 450gr projectiles outperformed his 500gr projectiles. Properly designed the lighter projectile can equal the penetration of the heavier one and if the design is significantly better the lighter one can actually out perform the heavier. I don't think he imagined this observation. SD has nothing to do with this.

Notice I refer to light and heavy projectiles. Not lower and higher Sectional Density. Newton's Laws do not utilize Sectional Density period. Referring to SD's value in such examples utilizing Newton's Laws simply confuses the issue when you are in fact only using the mass of the projectiles. Do not use SD and Mass interchangeably, it is not appropriate.

Yes it is true that a lighter bullet can penetrate as deep as a heavier one, and here is the reason why:

Cal ----- BW ---- V ---------- Mo ------- Xsa --- Mo/Xsa
.458 --- 500 --- 2000 --- 142.857 --- .458 --- 312
.458 --- 450 --- 2222 --- 142.843 --- .458 --- 312

I do not place much value on temporary cavitation (i.e. tissue stretch) created by small bullets at high velocity; its value is way over rated. Tissue is primary viscous with lots of cohesion and good elastic properties - body tissue like skin, muscle, bowel wall, lung are soft and flexible. Temporary cavitation is in most cases just pushing tissue aside. I much rather rely on permanent cavitation (i.e. tissue crush). If the tissue crushed by a projectile includes the wall of the aorta, far more damaging consequences are likely to result than if this same projectile "deposits" the same amount of energy beside this vessel. This implies either a bigger bore bullet or a smaller bore bullet that expands (i.e. greater Xsa). This is in fact the reason why so many bullet manufacturers have changed over to make controlled expansion bullets (CEB's), as they have listened to their customers hunting antelope. The likes of Swift A-Frame and NF cannot be on path that leads them to be less effective.

I do not like petals that fly off within the first inch or two. The wounding contribution of individual fragments show very little appreciable temporary cavitation effect, and its permanent cavitation effect is not something that I hang my hopes on; they lose their velocity and energy fast, penetrate little and veer off course. After loss of petals, we sit with a cylinder shaped projectile that makes a smaller hole than a CEB. The CEB, by virtue of its expansion and keeping its petals intact, require greater momentum to drive the bullet deeper (at least to the opposite side of the animal). Thus we need a higher SD bullet. I much prefer a CEB going through the vitals (heart/lung area) with its petals at its widest expansion to severe organs. A heavy bullet at modest velocity will do more lethal damage than a fast light-for-caliber bullet (read low SD)

In our current ballistic model of total energy and momentum conservation, projectile mass is favoured in lieu of velocity in penetration. Higher projectile mass per caliber translates to SD. Which projectile (made from brass) would penetrate the deepest when shot at the same velocity:

a) a round ball weighing 500 grains - featuring poor SD or
b) a bullet weighing 500 grains - featuring better SD ?

The latter, as we put more weight behind its frontal area.

Warrior

Chris/Warrior/Truvelloshooter,

quote:

Yes it is true that a lighter bullet can penetrate as deep as a heavier one, and here is the reason why:

Cal ----- BW ---- V ---------- Mo ------- Xsa --- Mo/Xsa
.458 --- 500 --- 2000 --- 142.857 --- .458 --- 312
.458 --- 450 --- 2222 --- 142.843 --- .458 --- 312

It is then logical that the lighter bullet will cause the same permanent cavitation as the heavier one and because it has to have more energy if it has the same momentum, it will cause a larger temporary cavity. Good point you make there.

quote:

I do not place much value on temporary cavitation (i.e. tissue stretch) created by small bullets at high velocity; its value is way over rated.

Tell that to the ground squirrel, the elk and the caribou below. Also, what broke the ribs in the last set of pictures? You clearly have no idea of the damage that temporary cavitation can cause. You should try some bullets that will allow you to gain some experience with this.

Before

After


Here is a description of a neck shot on an elk with a 7mm 130gr GSC HV: "This bullet entered the right side of his neck, traveled through the jugular then trachea (nice holes by that time), then damaged both the carotid and jugular on the way out, leaving a hole large enough to stick two of my fingers in on the exit side. The neck shot did not hit any bone."

Caribou - entrance 7mm 130gr GSC HV


Ribs broken by magic or by cavitation?

quote:

Temporary cavitation is in most cases just pushing tissue aside.

In your slow and heavy bullet world, I agree.

quote:

I much rather rely on permanent cavitation (i.e. tissue crush).

Which, as you say yourself, is the same with the lighter and heavier bullets. (See point one of this post.)

quote:

If the tissue crushed by a projectile includes the wall of the aorta, far more damaging consequences are likely to result than if this same projectile "deposits" the same amount of energy beside this vessel. This implies either a bigger bore bullet or a smaller bore bullet that expands (i.e. greater Xsa).

You need to think about this and rephrase the statement, you are not making any sense.

quote:

This is in fact the reason why so many bullet manufacturers have changed over to make controlled expansion bullets (CEB's),

I can not speak for others but we did not change over to making controlled expansion bullets, our HP and HV bullets always worked this way.

quote:

I do not like petals that fly off within the first inch or two.

Who cares what you like, as long as it works. But, as a matter of interest, why would you say petals come off in the first inch or two? Under what conditions would this happen and to what kind of bullet?

quote:

The wounding contribution of individual fragments show very little appreciable temporary cavitation effect

Tell that to this springbuck.

quote:

they (the petals)lose their velocity and energy fast, penetrate little and veer off course.

Sucking your thumb again because you don't know for sure but that is what you think must happen. Here is some actual experience with what petals do when they come off the bullet:
Recovered bullets by max diameter and description of remains:
1600 fps: .659" = 167%, expanded down two-thirds of hollowpoint, symetrically, with 3 petals partially folded back.
2500 fps: .768" = 194%, broke off 2 of 3 petals, petals found in third bucket with bullet, one petal still attached.
2725 fps: .554" = 140%, blew off nose and left a widened, nose-heavy penetrator, one loose petal found on ground beside bucket train.

quote:

After loss of petals, we sit with a cylinder shaped projectile that makes a smaller hole than a CEB.

This sentence is incomplete. It should read: "After loss of petals, we sit with a cylinder shaped projectile that continues on and makes a smaller hole, as it continues penetrating much deeper than a CEB, for a total wound channel volume that is bigger than that of the slower heavier bullet."

quote:

The CEB, by virtue of its expansion and keeping its petals intact, require greater momentum to drive the bullet deeper (at least to the opposite side of the animal).

Another incomplete sentence. Here is what it should be: "The CEB, by virtue of its expansion and keeping its petals intact, will give less penetration because it requires greater momentum to drive the bullet deeper (at least to the opposite side of the animal)."

quote:

A heavy bullet at modest velocity will do more lethal damage than a fast light-for-caliber bullet (read low SD)

You do come up with some silly statements. Didn't Rat Motor ask you a question along these lines that you have not answered yet? Here it is:

quote:

Hey Warrior,
Would you use a 175gr Barnes bullet loaded to 1300fps for kudu at 100m with your 7x57 or would you use a 140gr Barnes loaded to 2600fps? (1300fps is not a typing error). Motivate your choice using the SD as reason please.

quote:

In our current ballistic model of total energy and momentum conservation, projectile mass is favoured in lieu of velocity in penetration.

You have learned nothing from this thread, as usual, because we discussed the fact that, if the higher speed bullet gives sufficient penetration, the higher energy value causes a larger temporary cavity and, as we have seen, this contributes to the lethality of the shot. This renders your question about balls and bullets irrelevant, as it has on the past four or five occasions where you put forward that simplistic idea. In fact, you have said yourself that this is a stupid position to take when you made this statement:

quote:

The stupidity of making SD an absolute figure can be seen in the comparison of two bullets; one made from very soft rubber and the other from copper. The rubber bullet will probably bounce off the target, whereas the copper bullet will penetrate and cause severe damage.