.

Alf,
It is probably just a slip on your part but, for the record, we make no brass bullets.

Your example of two 44 bullets at equal velocity is erroneous. If you reduce an experiment to one non-deforming bullet of a particular SD and observe the penetration at a particular speed, you will find that the same bullet fired at a higher or lower speed will penetrate differently. You can do this 10 times or a hundred times at different speeds with one bullet and get different penetration results every time you change the speed. If the SD did not change over a hundred different shots fired with one bullet, but the penetration depth did, how can SD be the cause of varying penetration levels?

By the same token, if you can get deeper penetration with with a low SD bullet at a higher momentum level than with a high SD bullet at a lower momentum level, what does that tell us?

SD simply does not form part of the momentum or energy formulae.

MacPherson's book takes into account the full spectrum of of projectiles from non-deforming steel balls and cylinders to jacketed bullets and through to pure lead bullets and balls. He draws his conclusions from speeds ranging from a couple of hundred fps to speeds exceeding 4000fps and from impacts observed on a wide variety of media. In the acknowledgements, amongst others, MacPherson pays tribute to Dr. Martin Fackler, John Hess (Applied Mathematics and Fluid Engineer) and Dr Walter Gelon (Aerospace Engineer). It remains the definitive work on the subject and the laws of physics do not change.

.

Alf, I should have qualified my statement. The heavy bullet will penetrate better. Your conclusion (SD is the reason) is erroneous. The heavier bullet penetrates deeper because of higher momentum.

Bear with me and we will do this one step at a time. Using a box of identical undeforming bullets and the same impact medium, we fire one bullet to impact at 1000fps. We will get X penetration.

We load for the next shot and fire the bullet with an impact speed of 1100 fps. Will the penetration increase, decrease or remain the same?

Some basic facts.
Penetration is a function of momentum.
Wound cavity volume is a function of energy.
For any given bullet material for a given caliber increasing SD increases the length, and weight.
As a bullet expands the SD reduces.
All of these effects are occuring at the same time.
This allows room for any number of arguements.
Good Luck!

Posting for Chris Bekker:

Gerard,

You keep on trying to shift the arguments and to misconstrue what I am telling you. No matter how Alf presents his case for the validity of SD, you reject it. That is part of your shifting nature to twist what people tell you and then you try to lead readers onto another path in an incoherent fashion. I proved to you that momentum is only one of the drivers fitting into the holistic and complex dynamics of penetration. It is not absolute, just like SD is not absolute. SD cannot be used on its own - it is only one part of the greater picture. You still seem unable to see the relationship between SD and XSA, but accuse me of fuzzy logic. SD is the relationship of weight to frontal area and XSA is just the frontal area. You are just being a dickhead to make out that you do not see the relationship. When I used the round ball vs the bullet as an example to indicate shallower penetration, despite the same level of momentum, you can equally well extend that to a bullet that expands to a larger diameter. That shows that frontal area is an inhibitor of penetration and that happens with expanding bullets - the bigger the expansion the shallower the penetration. XSA is a critical factor in penetration dynamics alongside momentum, SD and construction of the bullet. In high-SD bullets we are putting more weight behind the bullets frontal area to aid penetration - it is that simple. Momentum over XSA is a better measure than just momentum on his own - I hope you can see this, but you keep on telling me that I should have only looked at momentum. Please don't try and confuse us with the 'facts'. Dr Norbert Hansen is also a supporter of Momentum/XSA and he does differ with Lutz Moller about penetration mechanics - so please do not bullshit the readers. I also never said that SD was a force - SD is a static ratio of a bullet that is not even in motion. You are willfully deceptive in twisting in what I am telling you in an attempt to ridicule - you are not succeeding. I hope the readers can see clearly what you are doing. Gerard you should know better that I will not let you get away with your crap.

Gerard you are known for launching character attacks on people including Dr Mauritz Coetzee and now you are trying to project it onto me - there is a word for that psychological literature that describes this devious behaviour. I find you over-sensitivity quite amusing regarding the relative smooth bullet of Lutz Moller versus the Impala bullet - you immediately try to make a point of that as if that is an issue? What is the point? The bullets look very different - any one can see the Impala bullet has deep grooves that run in a reversed way with a sharp cutting edge unlike Lutz's design. (I did not even refer to your bullet other than saying his bullet is close copy of your bullet which you claim was stolen from you). This just goes to show how petty you can be and to make non-issues the real issues - shifting and manipulating to confuse people of the real issues.

Why are you scared to admit that SD plays a role in penetration? Are you scared it would hurt the sale of your light-for-caliber bullets? It should not because you can drive the momentum value up with velocity - so what is the problem? Frangible bullets (bullet construction) that shatter, loose their effectiveness despite having a high SD. Mono-metal bullets do not suffer this fate to the same extent even if they lose their petals which vary from 15 to 23% depending on design. So all the key parameters need to be considered in an holistic approach to describe penetration characteristics. So the subject is more complex than it seems. There is absolutely no point to engage with you in any further talks, if you cannot see the above simple logic!

Chris

.

CAT FIGHT!!!



-Bob F.

Chris,
I ask a couple of simple questions each of which you should be able to answer in one sentence or with a "yes" or "no".

1. You say for the second time "but you keep on telling me that I should have only looked at momentum." Show me where I said that.

2. You state above that you were talking about Lutz's bullet when you mentioned a smooth bullet in your article. Here is the quote from your article: " Unlike the smooth surface of the GS-HV, the Impala Bullet provides......" Were you mistaken then or are you mistaken now?

3. In a previous post you state: "XSA is related to SD, not so? That's why momentum/XSA attempt to bring in both parameters by describing the force applied over the area." Is this fuzzy logic or not?

The rest of your emotional tirade is ignored.

Alf,
In my previous two responses to you, I gave you a qualified answer to every question you put to me. The principal reason why we still differ in opinion, I think, is because I have asked three questions of you which you have ignored. Slow down, consider my questions and give me the courtesy of an answer as you see it. That way we can structure a logical and unemotional discussion.

My questions were:

1. If the SD did not change over a hundred different shots fired with one bullet, but the penetration depth did, how can SD be the cause of varying penetration levels?
2. By the same token, if you can get deeper penetration with with a low SD bullet at a higher momentum level than with a high SD bullet at a lower momentum level, what does that tell us?
3. We load for the next shot and fire the bullet with an impact speed of 1100 fps. Will the penetration increase, decrease or remain the same?

Your last post essentially states two scenarios and you challenge me to prove you wrong. If you insist
Scenario one: You describe a trend whereby penetration seems to increase as SD is increased. If we ad a further example to your trend experiment by adding a .50 cal 400gr bullet at 2000fps, the trend further reinforces the SD connection as the .50 caliber will penetrate even less than the .45 cal bullet.

If we know what the density of the test medium is, we can calculate the penetration depth and come up with a number for each of the three bullets. (Can someone with the formulae at hand please do this. It is beyond my mathematical ability.)

This number will closely follow the ratio of momentum to cross sectional area of the bullet not the SD.

Remember that until now we have not introduced caliber variations into our discussion. Where the same caliber and bullet construction is compared, using only momentum as a penetration indicator is sufficient.

As soon as caliber is changed, that must be considered for the prediction to hold water. If the further variation of construction type is added, form factor must also be considered and sixpacks must be broken out.

Scenario two: You say: " Penetration is a direct function of terminal SD." Now you have to answer a question again. Use a type of bullet that has the same SD and terminal SD. (It does not deform) Fire two shots in succession, or three or four, increasing the speed by 50fps every shot. Which bullet goes deepest and why?

Bob F.
Catfight indeed. Can I help it if poor Chris gets so worked up?

IMHO,

1) Gerard is right
2) Chris is wrong, but well intentioned
3) Alf, idem 2

Of course to understand this a brief lecure on penetration mechanics will help

tks!

quote:

Originally posted by Gerard:
This number will closely follow the ratio of momentum to cross sectional area of the bullet not the SD.

The ratio of momentum to cross sectional area is exactly equal to the velocity times the sectional density.

(m x v)/A = (m/A) x V

Where m is the mass of the bullet, v is its velocity, and A is its cross sectional area.

The two derived quantities you are arguing about, momentum and sectional density, are the product of the mass with the velocity and the ratio of mass to cross sectional area, respectively.

momentum = m x v
sectional density = m/A

H. C.

.

quote:

Originally posted by Gerard:
By the same token, if you can get deeper penetration with with a low SD bullet at a higher momentum level than with a high SD bullet at a lower momentum level, what does that tell us?

This seems to be quite an argument, an argument with many of the variables left out!

Disregarding the non-deforming projectile as Chris' article mentioned talks of "X" bullets; let's look at a bullet's path from impact to stoppage.
Many, many are the variables here! A mushrooming bullet develops a "frontal area" over length of penetration. How fast this frontal area develops is a factor. The shape of the frontal area....... Its coefficient of form from how flat, how big, how rounded the radius; all variables! B.C. matters and is a varible too. So is density of the material period! A longer LIGHTER projectile has more friction penetrating because of more surface area along the shank. Penetrating rounds use tungsten because of its density. so now a less dense copper alloy penetrates better than denser lead being in the equation? Not unless it gains it with some other variable we haven't seen or have overlooked!

Chris tried to keep his frontal areas equal in his article hence the slower speeds. But even this isn't an exact. Velocity will "setup" the same constructed bullet sooner, maybe, hum another variable.

So if you drive a like mushrooming bullet FASTER it will penetrate deeper? Not proven in the formulas I seen here. It would be almost impossible to duplicate the time,distant, frontal area curves with the higher speed. If you did by some miracle then added speed would be added penetration.

The complexities are enormous as to variables to chart out any real data.

Frontal areas are really why we have an expanding bullet in the first place. Trauma, tissue damage, hemmorrhage, and an ulitmate timely kill are what we are all after.

The bigger the frontal area (and the sooner)with adequate penetration the better. The only deep penetrating light weight monolithic bullets accomplish such by having less frontal area for some, most, or all of the wound channel; or losing it along the way; again, a sea of variables involved for a scientific comparison that is absolute.

BigRx

.

Posting for Chris Bekker:

Gerard,

1. Answer to question 1:

In your very first post you wrote: ... "He goes through a lot of massaging and convolution to try and link SD to the penetration numbers. As he is so fond of "indexing", all he had to do was take the momentum numbers and "index" them to arrive at:" This states categorically that you focus on MOMENTUM and that you ignore Momentum/XSA. The massaging part escapes me totally as that implies fabricating to achieve a pre-conceived result. Convolution hints at me complicating unnecessarily, but that is not the case and simplified it step for step so people can follow me. The essence here is that you ignore the logic of the force applied (momentum) over the frontal area (resistance)


2. Answer to question 2:

On checking I found I did write GS-HV, my apology. In essence your bullet is very similar and so I do not think the word smooth is derogatory. I could have said the Impala bullet has a rougher surface. This is not an issue for me.

3. Answer to question 3:

Mo/XSA is not fuzzy logic - why should it be? Momentum is the force and XSA is the 'resistance factor' that must be overcome. Let me explain again. You admitted that a heavier bullet (high-SD) in Alf's scenario will penetrate deeper, but you attribute that to higher momentum and not SD. That is essentially correct, but the mass in the momentum formula (M x V) is linked to SD (Mass/D x D) and SD is also linked to XSA (DxD). XSA is the inhibiting factor. You seem to ignore this critical link. That is what I proved to you with the round ball and bullet scenario that had the same momentum - the bullet with its smaller XSA will penetrate deeper. We can also use a .458 bullet cut down to 180 grains and do a shootout with a 308 Win using a 180 gr bullet at the same velocity to keep the momentum the same. Guess which one will penetrate better? So, momentum is one driver and XSA is another driver and when both is considered it makes for a better measure than just momentum. Momentum has to be a driver because it captures mass and velocity.

By increasing SD for a given diameter (frontal area) we put in essence more weight per square inch behind the XSA and that results in better penetration. This is a fact. That means SD is implicitly involved but not a driver in the true sense. However, it is the factor that links mass with diameter. For simplicity we assume construction of bullets are the same, otherwise it becomes a driver as well. The form of the nose also plays a role as shown by Norbert Hansen, but we keep that also the same for simplicity. Also increased velocity in a given cartridge generally cannot make up the lost momentum value by going lighter on bullets. Let us look at an example where we push a 7 x 57 mm to its limits:

175 gr @ 2,450 fps = 61.3 Lbs/ft-sec
120 gr @ 3,100 fps = 53.1 Lbs/ft-sec

Again, that plays in favour of heavier bullets. That is why we say in general terms that higher SD assists with penetration. The fact remains we can prove positive correlation between SD and penetration depth in actual tests. If you prepared to take a second bond on your house I can do the test described above with the cut-down .458 bullet.

Chris

Hi Chris,
Nice try at trying to evade question one but I will not let you get away with it.

The question was: You say for the second time "but you keep on telling me that I should have only looked at momentum." Show me where I said that.

Question two: This is not about being derogatory, it is about the mistakes you make and getting huffy when your mistakes are pointed out. You profess to be a technical journalist. In technical writing it is vital to be meticulous about detail otherwise you promote confusion. That is the cardinal sin in technical journalism.

Question three: More evasion that you are not going to get away with. The fuzzy logic I quoted you on, is where you say Sd and XSA is related. One is a ratio and the other describes a surface area and through some magic you imply that is linked to force. Now you conveniently leave the embarrasing bit out. Nice try but it won't fly.

Finally you say: "The fact remains we can prove positive correlation between SD and penetration depth in actual tests."

That is not what your project X showed. Your article proved that depth of penetration of the various weight X bullets coresponded exactly to momentum and momentum/XSA, not to Sd. Below is the table from the article you wrote, showing the correlation to penetration, Sd and Mo/XSA. To this we can ad the indexed momentum values of

Bullet/Momentum/Index
175-----59.75----100
142-----50.51-----85
108 ----40.27-----67



Look at the examples we have concocted over the lenght of this discussion.

Without changing Sd, you can make a particular bullet penetrate more or less.
You can increase the Sd of two bullets and one could be made to penetrate less and the other could be made to penetrate more.
You can decrease the Sd of two bullets and have one that penetrates more and another that penetrates less.
You can have two bullets with differing Sd values that penetrate to exactly the same depth.

How you can make a link between Sd and penetration from all that, other than a coincidental one, is a mystery to me. I look forward to your next article in SA Hunter. Mainly I am curious to see what kind of rifle you are going to shoot those square cylinders from.

Alf,
As you are leaving, allow me to summarise.

Look at the second last paragraph of Lutz's article where he says: "an increase in mass per cross sectional area keeps the bullet moving." That is the flaw. What keeps a bullet moving is not mass per cross sectional area, it is momentum per cross sectional area. In his last paragraph he states: "depth of penetration depends directly on terminal SD." Wrong again. Depth of penetration is derived from momentum per cross sectional area after the bullet has deformed, modified by a shape factor which cannot be accurately calculated. That is why we fret about "non deforming bullets" in discussions such as this.

An anecdote is appropriate and Chris could confirm this with Lutz if he likes.

I invited Lutz to come and hunt with us in 2002. He spent 5 days with us and we went after springbuck, blesbuck and kudu. I explained beforehand that the springbuck shooting was a cull hunt for meat and nothing special, but made him a present of a walk and stalk on a blesbuck and another on a kudu. When I picked Lutz up at the airport, he only had one rifle with him. Apparently his 8mm did not get onto the flight as he was overweight on luggage and he only brought his 6.5x65 RWS. His ammunition was 110gr jacketed soft nose bullets loaded to well beyond 3000fps, as I recall.

That evening at home, when I said that he could borrow one of my rifles for the kudu, he said it would not be neccessary as the 6.5 would be ok. He proceeded to log on to his website and showed me that, according to his calculations, the 6.5 is adequate. I politely disagreed with him and told him that he will use one of my 7x 57 rifles. As it turned out, he shot a couple of springbuck, a very nice blesbuck that just makes Rowland Ward but unfortunately no kudu. The terrain was mountainous and he never got off a shot. Was I wrong in not trusting his calculations about the 6.5 and the kudu, I think not.

The bottom line is that SD, by it's very definition is not a force. It cannot do work and is not contained in any formula that equates to work being done or the ability to do work. Sd only tells us how much floor space the object takes up while giving a reading on a scale.

I understand how one clings to concepts because "It has always been so." We all believed in hydrostatic shock, enrgy dump and heavy bullets for shooting in the wind, at some stage. Looking back at shooting thousands of bullets of all types into sand, water, wetpack, drypack, clay and animals over the last 25 years, has convinced me that it is time to relegate Sd to the same scrap heap.

I've been reading with utmost interest the last posts. I´ve a strong technical side and so I enjoy this threads very much!

I refuse to give much opinion here, since I'm not one of the main "guests" but I still believe that the logic posted by Gerard is the right one.

The other posts, especially the material by Herr Möller while very informative, are simply a nice try.

Think for a moment on the factors that affect penetration (weight, form, material, construction, speed and the same for the target ) and figure out two bullets of the same diameter, weight...but one of a conventional material and the other one of butter.

Both will have the same SD, don't they?

Well, of course not the same KE, Momentum of any other force we can think of. Go figure!

A simple way to visualize where to leave SD ... where it belongs... the scrap heap (sorry Gerard that I stole your phrase!)

quote:

Originally posted by HenryC470:

quote:

Originally posted by Gerard:
This number will closely follow the ratio of momentum to cross sectional area of the bullet not the SD.

The ratio of momentum to cross sectional area is exactly equal to the velocity times the sectional density.

(m x v)/A = (m/A) x V

Where m is the mass of the bullet, v is its velocity, and A is its cross sectional area.

The two derived quantities you are arguing about, momentum and sectional density, are the product of the mass with the velocity and the ratio of mass to cross sectional area, respectively.

momentum = m x v
sectional density = m/A

H. C.

Sectional density assumes a square bullet. It is a flawed artificial/arbitrarily defined term, with no real physical units. One of your equations there is not true. Which one?

Gerard is correct in recommended reliance on real values like momentum insteadf of the concocted Sd.

Why we refuse to understand that SD has no play with penetration? Is it so hard to accept that our previous knowledge is wrong, that we must revise all of our believes from time to time ?

Imagine that! we will still using muskets or arrows or stones!!

Please, just a little moderation here... there is no case in arguing that SD means more than nothing...

Do we need more proof?

Gerard, hope you and the others, will cross the pond someday to have a taste of our Red Stags!

PS: to Chris and Alf, don't feel beacuse of some comments, we area all here to help each other through this kind of discussion. It is good and makes us more knowledgeable

Ja,
Sd is not totally useless, but would be more useful and applicable if defined as a round cross sectional area instead of a square bullet XSA. At least it would have real units then.

Posting for Chris Bekker:

Purist will always insist that XSA be calculated the correct way, which is Pi multiplied by the Radius squared, and not by diameter squared that overstates the value somewhat and hints that we are supposedly shooting square bullets. The same principle applies to SD. No one can actually argue with this. However, I guess it was probably done for simplicity sake in ballistic literature just to explain the underlying logic and not to be absolute perfect.

When my test values are adjusted to achieve the same momentum value, it does show that by linear extrapolation with the derived factor of 11.8 it yields the same penetration depth for all 3 bullets, provided the bullets do not expand or expand to the same diameter. Sure that proves that momentum is the driver (driving force) and not SD. SD is only implicitly involved. Also, when the XSA expands to a larger diameter (inhibiting factor), the momentum is spread over a larger area and so penetration suffers. That makes XSA also a driver, even though it is not a force nor used in any formula that describes the ability to do work. SD only links up as it has a mass component and a frontal area component, but the absolute values are trapped in Mo and XSA. The equation below shows that when SD is multiplied with velocity we also get the same answer as Mo/Xsa:

(M x V)/(D x D) = M/(D x D) x V
Mo/XSA = SD x V

Let's test the formula that contains SD as an element, with the new increased velocities (ignore rounding differences as we did not express velocity to the 3 rd decimal value to equate 100%) just to make sure:

SD Velocity Mo/Xsa
.310 x 2,200 = 682
.252 x 2,712 = 682
.191 x 3,565 = 682

Mass Velocity Momentum Mo/Xsa
175 2,200 55.0 682
142 2,712 55.0 682
108 3,565 55.0 682

Penetration = (Mo/Xsa)/11.8 or (SD x V)/11.8 yields the same answer of 57.76

We can thus conclude:
Momentum and XSA are the prime drivers in penetration dynamics.
SD is implicitly embodied in the above two factors, but it's not a prime driver.
By driving velocity up with low-SD bullets, a Mo/XSA equilibrium can be reached.
The above increases in velocity cannot be reached with the same cartridge/rifle.
Thus increasing a bullet's SD has value in a given rifle, as it will always yield higher momentum.
These increased velocities seriously diminish bullet performance in lead-core bullets.
Low-SD bullets are destined to be for mono-metal bullets at high velocity.
High-SD bullets work better in Soft configuration at modest velocities.
This is a typical position fot a 7 x 57 mm mauser, when we use Impala's 110 gr bullet with 43.0 grains of S341 for a recommended velocity of 2,870 fps. I am getting 2,450 fps with 175 grainers, but I only load to 2,350 to 2,370 fps.

175 gr @ 2,350 fps = 58.8 Lbs/ft-sec
110 gr @ 2,870 fps = 45.1 Lbs/ft-sec

The thrust of this discussion over the last weeks was a pure focus on penetration, which is only part of a bigger thorny issue as to killing more effectively. Does the size of the hole count? Does the bullet that expands to double caliber perform better than a non-expanding solid when it goes through the heart or lungs? Does a flat-faced cylinder at high velocity make a bigger permanent cavity than a controlled expansion bullet that expands to 2.4 times original diameter?

Chris

(M x V)/(D x D) = M/(D x D) x V
Mo/XSA = SD x V

Is not correct.

The accepted formula for Sd is as above (M/D^)
The accepted formula for Mo/XSA is (MxV)/(Pi r^)

Also I see:
"We can thus conclude:
Momentum and XSA are the prime drivers in penetration dynamics.
SD is implicitly embodied in the above two factors, but it's not a prime driver.

I have to go lie down now.

II.c. Mechanics of Penetration

Penetration is simply the depth to which a bullet passes through a target.

Factors affecting penetration for modern weapons, in order of importance are: 1) bullet construction, 2) bullet shape, and 3) impact velocity. In general terms velocity is the most important factor, but most rifle cartridges develop similar velocities, so within this typical range of interest, as we will see, other considerations prove more significant.

Bullet construction is the most important factor because it will determine whether the stresses of impact allow the bullet to overcome the resistivity of the target. In other words, is the bullet tough enough to survive the impact and penetrate, or will it shatter, and if so, how far will the fragments penetrate? Advances in metallurgical processing of bullets have made contemporary designs superior to anything used in the last century, giving small-bore bullets the effectiveness of huge lead balls. The target material will greatly affect the selection of bullet material, but in general, toughness (malleability) is more important than hardness. Other features, such as bonded cores and tapered or partitioned jackets permit greater penetration by controlling the expanded presented area and retaining bullet mass.

Bullet shape is next in importance because a pointed bullet which does not deform becomes unstable at impact velocities of interest and will not penetrate as deeply as a flat-nosed or round-nosed bullet of the same weight and velocity. Non-deforming round nosed bullets generally penetrate more deeply than flat-nosed bullets, depending on the width of the flat nose and the radius of the round nose. Since nearly all rifle bullets today are pointed designs intended to deform, bullet shape also applies to expanded or fragmented bullets.

Sectional density is bullet weight divided by the diameter squared. In simplistic theory, it describes the relative ability of a bullet or fragment to penetrate. For a given caliber, the heavier bullet will have a higher sectional density. However, this value does not consider bullet construction, the shape of the nose or the effect of ablation (loss of bullet mass). At impact, the effective sectional density becomes the retained bullet weight divided by its expanded represented frontal area (which initially is smaller than the nominal caliber). Thus, practically speaking, two bullets having the same sectional density can have very different penetrations after impact, depending upon their shape and toughness. Sectional density is a misleading indicator of performance for bullets of different constructions and materials; sometimes even for similar apparently designs. Varmint bullets have low sectional densities, but even these values suggest better penetration than they are capable of providing when compared to big-game bullets of heavy jacketed, bonded core or monolithic construction. Similarly, the stronger premium bullets (such as the Barnes X-Bullet) are capable of penetrating as deeply as bullets of conventional construction having much higher sectional density.

Finally, impact velocity determines the hydrodynamic pressure, which may be thought of as the resistance to penetration encountered by the bullet. Impact velocity has a significant effect upon bullet deformation (involving both bullet construction and shape), but beyond this it also affects the amount of cavitation caused by the bullet in tissue. In theoretical terms, a projectile creates a cavity which is proportional to its kinetic energy (actually, the permanent volume of the cavity may be considerably less than the theoretical expected volume). The cavity extends radially (what I term cavitation) and along the path of the bullet (penetration). The more it cavitates, the less deeply it penetrates. High velocity can have a detrimental effect upon penetration in a fluid, due to the "splash effect". It can destroy the bullet or cause it to create an enormous cavity without penetrating (which is not necessarily undesirable in certain tactical situations).

Most rifle bullets are designed to perform reliably within a rather narrow range of velocities, usually 2000 to 3000 fps for most conventional rifle bullets. Below this velocity range, the bullet may not expand; above it, the bullet may shatter on impact. This is a limitation imposed by material properties and design characteristics. For this reason, bullets which are intended for pistol hunting loads would be inappropriate for use in high velocity rifles, since their impact velocities would be very much higher than those they were designed for (although they may perform perfectly for long range shots where the velocity has moderated). Other bullets, referred to as "custom" or "premium" designs, can be successfully used for a wider range of impact velocities, perhaps as low as 1700 fps and as high as 3300 fps (though most designs tend to work better at one end of the velocity spectrum than the other). They are typically designed to expand easily at low velocities but retain their weight (at least most of it) at high impact velocities. Bullets designed for the older low-velocity rifle cartridges and for handguns can be relied upon to expand down to about 1400 fps in the case of rifles and 900 fps in handguns.

Against hard solid targets, such as armor or heavy bones, high impact velocity is the most important factor contributing to maximum penetration (assuming that the bullet remains intact), because this has a shattering effect upon the material. Maximum penetration in a fluid medium, however, is achieved when cavitation is held to a minimum, as in the case of a non-deforming, round-nosed bullet travelling at "moderate" velocity. Heavy big-bore, flat-nosed, hard-cast lead-alloy bullets are favored by handgun hunters for large game because they are more efficient than jacketed soft points. The broad flat nose on the relatively large caliber bullet provides adequate cavitation, so expansion isn't necessary. Since there is no expansion, there is also no energy lost to bullet deformation ­ all of the remaining kinetic energy of the extra-heavy bullet is directed toward penetration with acceptable cavitation.

Posting for Chris Bekker:

Gerard,

I wish to highlight another interesting discovery that came to light. Look at the energy values ... whilst the energy formula is the most scientifically correct formula to describe the ability to do work, it does not accurately predict penetration levels. Momentum does a better job and further down I will demonstrate that Mo/XSA does an even better job.

Bullet / Speed / Momentum / Mo/XSA / Penetration / Energy/ E-Index
175 --- 2,200 ---- 55.00 ----- 682 ------ 57.76 ---- 1,881 --- 100
142 --- 2,712 ---- 55.00 ----- 682 ------ 57.76 ---- 2,320 --- 123
108 --- 3,565 ---- 55.00 ----- 682 ------ 57.76 ---- 3,049 --- 162

The above values of Mo and Mo/XSA are the same for all bullets only because the XSA stayed the same throughout as expansion was not varied. Just a word to elaborate on the interaction between Mo/XSA and SD. Whilst Mo and XSA are both drivers, the real or final penetration indicator turns out to be Mo/XSA. Despite the fact that the XSA was calculated by D x D, the ratio of Mo/XSA correlated very well with penetration. To illustrate the link I am talking about, we need to do a table to model the effect of differing XSA's whilst keeping the momentum values the same each time. Consider a scenario where we cut .458 Barnes Solid down to 180 grains and do a shootout with a 180-gr Barnes Solid in .308 calibre. As the XSA of the .458 bullet is larger, it will not penetrate as deep as reflected by the Mo/XSA yardstick. In fact the Mo/XSA figure dropped to 45.2% of our base line (1 st rifle in table) and so does the SD. For brevity sake I will model only 2 scenarios comparing different bore diameters (XSA):

Example 1:
~~~~~~~~
Cartridge / Bullet Mass / Velocity / Momentum / XSA / Mo/XSA / SD
308 Win ---- 180 gr --- 2,625 ---- 67.50 --- .094864 -- 711.54 -- .271
458 Win ---- 180 gr --- 2,625 ---- 67.50 --- .209764 -- 321.79 -- .123
Percentage of base figure ************************* 45.2% -- 45.2%

Example 2:
~~~~~~~~
Cartridge / Bullet Mass / Velocity / Momentum / XSA / Mo/XSA / SD
30-06 Spr -- 220 gr ---- 2,415 ---- 75.90 --- .094864 -- 800.09 -- .331
375 H&H -- 220 gr ---- 2,415 ---- 75.90 --- .140625 -- 539.73 -- .223
Percentage of base figure ************************* 67.5% -- 67.5%


I could have elected to use one caliber throughout and just varied the expansion, but the principle is the same - a larger XSA inhibits penetration and therefore it is a key driver in penetration dynamics. Here you can see how SD varies in sympathy with Mo/XSA. Let me not be lazy and do an example with the same caliber but with 2.0 times and 2.5 times expansion of diameter (in this calculation XSA and SD should be based on its terminal measurements) like it typically happens in real life with Softs.

Example 3:
~~~~~~~~
Cartridge / Bullet Mass / Velocity / Momentum / XSA / Mo/XSA / SD/ Expansion
7 x 57 mm -- 175 gr --- 2,350 ---- 58.75 --- .322624 -- 182.10 -- .077 -- 2.0 x
7 x 57 mm -- 175 gr --- 2,350 ---- 58.75 --- .504100 -- 116.54 -- .050 -- 2.5 x
Percentage of base figure ************************* 64.0% -- 64.0%

From the above we can safely conclude that the bullet that expands to 2.5 times of original diameter will penetrate 36% less (100% - 64%) than the bullet that only expands to double diameter - XSA in action. Again SD varies in sympathy with Mo/XSA. The only time SD does not vary in sympathy with Mo/XSA is when there is no expansion of diameter and increased velocity must make up the lost ground for low-SD bullets to equal the same high momentum value of high-SD bullets.

Chris

Adding the energy column puts an interesting slant on those three bullets. If they all penetrate equally well, the lightest bullet with the highest energy value, will also cause the greatest hydrodynamic impulse, resulting in the largest wound cavity volume of the three. It will therefore kill most effectively.

From your last paragraph above, I deduce that we have come full circle to my original position that the Sd of a bullet sitting on the loading bench is irrelevant. It does not indicate the likely penetration of the bullet and will in any case change on impact to an unknown value or, in severe cases disappear completely.

I still think that we are overlooking the important factors... somehow we're trying to fit a nonsense idea into reality, playing with numbers, a very common misconception.

However I appreciate and value those efforts, because from them, arise the true

IMHO, no formula or whatever will be effective as long as it doesn't take into consideration, materials, construction, shape, etc

Please remember the "butter" bullet

Posting for Chris Bekker:

Gus and Gerard,

Gus, bullet construction is very important and it would be near impossible to assign values to them. In our discussion we used numbers to evaluate the main drivers of penetration and so we had to assume that all other variables stay constant for the sake of the debate. The durability of the bullet becomes an issue the moment its threshold strength is exceeded - its weight retention ratio, its rate of expansion. This determines the 'performance band' the bullet can operate within most effectively. Inherent in this are the materials it is made from and the thickness of jackets - gilding metal, tin or pure copper. Also the shape of the tip - some bullets do not expand at low velocities and are intended for extreme impact velocities (2,750 fps plus), like the Failsafe bullet. In contrast, Woodleigh bullets with ample lead exposure at the tip expand quickly and reliably at low velocity, but over-expand at high velocity. If the construction is weak (thin jackets, brittle lead and not bonded), like in conventional bullets, it cannot withstand the rigours of higher velocities of present day cartridges. Mono-metal bullets by design are much stronger. Yes formulas cannot trap all the imponderables.

The criticism that Gerard levels against Softs because they change their pristine SD in the terminal phase is really a one dimensional view as far as lesser penetration results from ever expanding mushrooms. Clearly this is related to bullet construction issues. However, bullet expansion is also a design criteria to increase the lethality of the bullet to make a bigger hole. We are essentially shooting bullets that expand because we want them to expand. Otherwise we should not shoot them at all, just like we do not wish to shoot rubber bullets that will bounce of an animal, whereas for crowd control it may be appropriate. So, SD changes during penetration is desirable and exactly what we expect from a hunting bullet. For extreme penetration requirements, nothing can beat a non-expanding mono-metal bullet. We have to recognize their are horses for courses.

Shooting a runaway buffalo from behind, through its huge grass-filled guts, and still expect to reach the heart with a large expanding Soft must surely be one of the dumbest things one can do. You still have a chance with a solid, but to gamble that the animal's hart is exactly in your line of fire in a gallop is yet another thing. Regularly we see and hear that buffalos run off with lung-shots administered with Solids. Some SA hunters shoot springbuck with varmint bullets at extreme velocities. When frowned upon, they tell you they go for lung-shots and it works for them. I have seen how conventional bullets mess up the frail bodies of springbuck - one cannot afford to loose meat on a small animal like that and mono-metals (Barnes-X, Impala and GS-HV) are arguably better matched if you want to put unspoiled venison on the table.

I do not buy in that high energy kills better. Even if they cause bigger craters on entry the theory is still suspect to me. These 'craters' or cavities are also very different for Softs vs Solids. Solids just zip through - I have never witnessed a crater. Softs that shatter, yes they create a mess and split up in multiple small and ineffective projectiles (lost momentum) and may not reach the vitals. Furthermore, the cell structure of animals is such that they do not react the same as when a can filled with water is shot, as they are compartmentalized at the micro level and are thus much more flexible than a homogenous fluid. With reference to Gerard's statement about the value of ENERGY, just the following perspective.Let us shoot solids with a .223 Super (hypothetical cartridge) and compare it with an old favourite, the 30-06 Spr. I shall keep momentum values the same, but over-energize the low-SD bullet:-

--- Cartridge --/ Mass / Velocity / Momentum / Energy /-- SD --
.223 Super ---- 55 gr --- 9,500 fps --- 74.64 -----11,025 --- .158
30-06 Spr. --- 220 gr --- 2,375 fps --- 74.64 ------ 2,756 --- .331

The energy value of the trusty old 30-06 Spr is only 25% of the 'mighty' .223 Super.
Would the .223 Super produce a better wounding and thus a better killing effect?
Seldom if ever, will a high-SD bullet not provide you with the desired result!
We should not ignore the numbers - they tell a story and should make us think about the relevance of the energy formula in a hunting scenario. Pretty useless if you ask me.

Chris

Posting for Chris Bekker:

Since we have some hard data on penetration that correlates very well with Mo/Xsa, it calls the Penetration Index (PI) calculation into question as it is based on energy. The PI formula takes only 10% of the energy value, multiplies it with the sectional density, and divides the answer with the cross-sectional area of the bullet. Not only does the energy premise bother me, but also the logic of the second term, which is SD/XSA. Formulating it this way means that we are dividing twice by the the bullet's frontal area. I can understand Mo/Xsa, which is what I have already proven. I think the time is appropriate to explore this matter further.

Formula 1:
************

PI = (10% of KE) x SD /XSA

A reader by the name of 'Will' posted another formula on AR that Art Alphin of A-Square fame is using and I quote him:

Formula 2:
************

"PI=(KE)(SD)/(100 A)

KE=bullet kinetic energy, ft-lb
SD=sectional density, lb/in^2
A=bullet x-sectional area, in^2"

The difference being that Art Alpin is dividing by 100 (or multiplying by 1/100), whereas in formula 1 we are multiplying by 10/100. Either way the question is ... if energy is so significant, why then only 1 or 10% of the Kinetic Energy? May be the division by 100 is just to get a more "manageable" figure. Be that as it may, I would like to see someone prove to me that the PI formula does in fact correlate well to my penetration test results iro the 3 bullets. Frankly, I cannot see it, but I will remain open minded. If the generally accepted Penetration Index is not a valid yardstick, then it is also time that we reject it.

Yours truly
Chris

Chris,

As long as we use any formula that doesn´t take into account materials, constructio, shape, etc, we are going to still trying to turn lead into gold...

I understand and share your comments on how difficults could it be to consider the variables involved, but to take a shortcut in order to have a formula at hand... well in my opinion that is not going make any science!

The real models as developed by the labs use many other variables and finite-elements computational models in order to predict within reason the behaviour of colliding objects.

Unfortunately, this sport is plagued by many, some of them writers of fame, that have no technical background and while valuable, try to make "formulas" out of nothing, creating "black magic" out of pure BS... correlating apples to eggs, and they do this simply because nobody out there cares.

In short, any model not only should correlate nicely with actual results, they also are useful to predict them, and must pass a series of questions and math analysis to thest the "robustness" and most important to test the "extreme points" in this case, a good example could be the "butter bullet"

Science history is full of many "models" that "fit" or at least makes sense... on the other hand, as mentioned before, we have in our sport tremendously wrong notions : "Killing Power", "Hydrostatic shock", "Lethality factor" and a plethora of "formulas" that any serious engineer or scientist could only take as jokes...at best

Chris,
Your .223 Super is an exellent example. It proves several points very nicely. I have often said that, if you want to test a theory, take it to extremes. If it holds water there, it is usually good theory.

Asuming for the moment that it would be possible to fire a bullet from a shoulder fired weapon at 9500 fps (what a thought!), the real scenario would be that the trusty old 30-06 would pale into insignificance as far as terminal performance is concerned.

Of course the bullets would have to exhibit similar deformation characteristics, say a double caliber expansion and similar weight retention, so your lead jacketed 30-06 bullet would be matched by a .224" bullet made from unobtanium and loaded with powder from the experimental program currently under way on Delta 17 in the sixth quadrant.

To your table we would ad columns for Mo/XSA and penetration which is estimated according to the constant factor of 11.8 for your test medium.

Cartridge -- Mass -- Velocity - Momentum - Energy --- SD -- Mo/XSA-- Penetration
.223 Super - 55 gr - 9,500 fps - 74.64 ----11,025 -- .158 --- 474 ------ 40.2
30-06 Spr. - 220 gr- 2,375 fps - 74.64 ---- 2,756 -- .331 --- 251 ------ 21.2

Whether you buy in that high energy kills better or not, it is documented fact that the wound channel volume is in direct relationship the kinetic energy. Regardless of the shape of that cavity, more energy equals more cavity volume. You ask the question: " Would the .223 Super produce a better wounding and thus a better killing effect?"

Based on the fact that the 22 bullet in your example will go almost double the depth with a much larger wound cavity volume, I think it would be fair to answer with a resounding YES. The other advantages of the additional speed of the 223S would be much less wind drift, unbelievably flat trajectory and time of flight so short, you could take running shots out to 500 with it.

Just in case you misconstrue the purpose of the above exercise, I must explain: It is patently clear that a bullet that is of superior construction compared to another, can do the same job or better, with less weight (and less of the mythical Sd).

Posting for Chris Bekker:

Gerard,

My question was ... Would the .223 Super produce a better wounding and thus a better killing effect? You answered ..."Based on the fact that the 22 bullet in your example will go almost double the depth with a much larger wound cavity volume. I think it would be fair to answer with a resounding YES." I beg to differ, as you seemingly gave no credence to the .308 bullet's larger diameter. Excess and unneeded penetration does not assist to kill better. You also assumed that the smaller caliber bullet at higher velocity would make a larger permanent cavity. Since the energy of the .223 Super was 400% higher than the 30-06 Spr. you need to prove a cavity 4 times as big to support your claim that ... "it is documented fact that the wound channel volume is in direct relationship to the kinetic energy". As the .223 Super does not exist as yet, even though you wish it did, I would like you to prove it in the following two cartridges that are readily available:

-- Cartridge --/ Mass / Velocity / Momentum / Energy /-- SD --
7 x 57 mm -- 175 gr -- 2,350 fps -- 58.75 -- 2,146.5 -- .310
7 mm STW - 120 gr -- 3,427 fps -- 58.75 -- 3,130.2 -- .213

The purpose here is not to show penetration depth (although they would be the same in this case, as Mo/Xsa is the same), but rather the size of the wound channel. I have done my test and shared it with one and all - now it is your turn to do this test and show me that you obtained a bigger wound channel. The energy in the faster cartridge is 45.8% higher, so I need to see a hole that much bigger. As you can't do this test with a Barnes-X that would shed its petals above 2,700 fps, I suggest you use non-expanding Barnes Solids to avoid other variables kicking in. Supporting pictures would be appreciated.

There is one more problem - we are talking about the killing effect and we cannot kill paper. The cell structure of animals is such that they do not react the same as when a can filled with water is shot, as they are compartmentalized at the micro level and are thus much more flexible than a homogenous fluid or paper. This is of vital importance ... how would these two bullets react when shot into living tissue?

In closing a 22 Cheetah can launch a 50 gr bullet at 4,315 fps for an energy level at 2,068 ft-lbs, whilst a 30-30 Winchester launch a 170 gr bullet at 2,090 fps for an energy level of only 1,649 ft-lbs. Based on your logic that the 25% higher energy cartridge will produce a bigger wound track volume, all the owners of 30-30's should trade their guns in for 22 Cheetah's. I do not believe you are going to have much success in convincing them.

Chris

quote:

Cartridge --/ Mass / Velocity / Momentum / Energy /-- SD --
7 x 57 mm -- 175 gr -- 2,350 fps -- 58.75 -- 2,146.5 -- .310
7 mm STW - 120 gr -- 3,427 fps -- 58.75 -- 3,130.2 -- .213

For a start, I would not dream of shooting a 120gr bullet from a 7STW at 3427fps. What would be the point? Alf managed to get 3750 fps with a 130gr bullet and dropping 10 grains off the weight will be good for at least another 100fps. I would also not use a 175gr monometallic bullet in a 7x57 as it will not stabilise sufficiently for decent terminal performance. The 175gr bullet in the comparison will have to be a bimetal bullet of some sort. So let us redo your table with real life values:

-- Cartridge --/ Mass / Velocity / Momentum / Energy
7 x 57 mm -- 175 gr -- 2,350 fps -- 58.75 --- 2,146
7 mm STW --- 120 gr -- 3,850 fps -- 66.00 --- 3,951

Are you seriously going to tell me that the 7x57 is going to be the more lethal of the two? Are you serious about your belief that faster bullets do not cause larger wound channels? If you are, then I must ask: How much hunting have you done?

The other part of this comparison is the external ballistics. This really blows the heavy bullet into the weeds. Both are zeroed at 200 and wind is 3 o'clock 15mph.

Cartridge -- Mass - Path @ 100 - Path @ 300 - Wind Drift @ 200 - TOF @ 200
7 x 57 mm - 175 gr -- +4.38" ----- -18.54 ------ 12.45" --------- 0.32637 sec
7 mm STW -- 120 gr -- +0.78" ----- -4.02 ------- -1.70" --------- 0.17689 sec

The test you require has been done and reported, not by me but by an independent tester. You would in any case not believe a test that I do, would you?

The rifle used was a 7-08, close enough to a 7x57 and the bullets used were Nosler Partition 175gr at 2400 fps and 120gr HV at 2910 fps. Penetration depths were identical and wound channel volumes were very similar. Given the speeds, expanded diameters and Mo/XSA of the two bullets, the penetration was precisely to be expected. Given the enrgy levels of the two, the wound channel volumes are precisely what was expected. So if you seriously believe that adding almost 1000 fps to the 120gr bullet will not increase the wound channel size or depth, I must question your lack of logic here.

I have no experience of hunting with a 30-30. I have lots of experience hunting with a 22x64 (it is like a 22 Cheetah on steroids). I have taken it afield in comparison with a 243, 270, 7-08 and 308. Up to blesbuck, it killed as effectively and was a lot easier to hit with, given the lack of drift, flat trajectory and short time of flight. Have you ever compared 5 or 6 different calibers side by side under actual field conditions on live game? I do it regularly. On the occasion above we shot a total of 72 springbuck over three days. Another such occasion, albeit curtailed, is reported here.
This type of testing is hard work, but someone has to do it!

I was on the range doing BC tests with .223 and a 40gr HV some years ago. I couple of guys came along with a 30-06 and 180gr jacketed lead bullets. After a while they were curious about what we were up to and I explained about the two chronographs and the wetpack to catch the bullets at 100 metres. They asked if I would take a couple of shots over the chronos with the 30-06 and I obliged. We used a 40cm wetpack at that stage and when we walked up to it, these fellows immediately looked at it from behind, expecting exit holes from the 30-06. We peeled off the layers and found the fragments of the 30-06 between 6 and 9 cm into the pack and we found the four 40gr HVs 13 to 15 cm in. The 30-06 was at a MV of just under 2700 fps and the 223 was going at 3800 fps. Go figure.

Posting for Chris Bekker:
Hello Gerard,

1. The only reason I pitched the velocity of the 7 mm STW at 3,427 fps was to keep momentum values the same to eliminate yet another variable. Similarly I can easily obtain a higher velocity of 2,525 fps with my 7 mm Mauser. I simply pitched the velocities at 2,350 and 3,427 fps merely for comparative purposes. Nevertheless, this test can be done with relative ease and might just give us a clue as to which way the wind is blowing.

2. I would have liked to see a test proving the energy theory of making a bigger cavity. In such a test it is important that we compare apples with apples - not a Nosler Partition with a GS-HV. So we can't just lean on this test that was done. Just like I did my test with 3 different bullet weights we should do it with 3 different energy levels. Also the other penetration test that you bring in as testimony is a skewed one. I am sure you can see the inequity in your penetration test comparing frangible Softs in .308 caliber with mono-metal bullets in .223 caliber and I surely need not to comment further on that as there is nothing to be figured out.

3. Once we have done a test in a certain medium (wet paper or ballistic gelatin) we still have to relate it to the wounding effect in animals. Cavities are not the same in living flesh as opposed to paper and water. We are talking about the killing effect in game so biology now enters the equation as well. I am now going to ask Alf kindly to come in here to give us a lecture on this issue as a medical doctor. I think most readers will gain a valuable insight from this.

4. Ok, let us move away from the 30-30 because you have not used that one. Let me use another one that you may be more familiar with - a 9.3 x 62 mm versus a 7 mm STW - you can drive both to max and ignore momentum values if that is what you want. The principle is actually the same. For the sake of the discussion I will pitch the following:

-- Cartridge ---/ Mass / Velocity / Momentum / Energy
9.3 x 62 mm -- 286 gr -- 2,250 fps -- 91.93 --- 3,216
7 mm STW --- 160 gr -- 3,200 fps -- 73.14 --- 3,639
More powerful ************************ 13.2%

Our target is an angry Cape Buffalo bull in the Zim Valley and Ganyana is our guide . Based on you preference (conviction) I am sure you would pick the cartridge with the lighter bullet at the faster velocity. Whilst underway in the Jeep to the hunting terrain, you can let ol' Ganyana in on the superiority of your energy theory and get a good chuckle out of him. Also steer him in the direction of the wonderful .223 Super with the possibility of reaching 11,000 ft-lbs making everything redundant and manufacturers will then be able to offer us only one cartridge from duiker to elephant - laugh out loud! After all we have been on the moon already and it should not be too outrageous. Needless to say I will pick the proven buffalo cartridge. What is more, I will not worry about the extra penetration afforded by a non-expanding solid, I will much rather opt for a strongly constructed controlled expansion bullet, such as the 286-gr Rhino Solid Hank bullet, that expands to 21.5 mm or 2.3 times of original diameter and its penetration has been proven as sufficient countless times. The critical element to recognize in this is the size of the hole through the vitals and not the deeper penetration of a non-expanding solid. To aid bigger expansion we generally opt for bigger bores that also provide more momentum as opposed to the misleading energy statistic of super fast cartridges. Most Softs are rendered useless anyway at close range with a MV of 3,200 fps against buffalo and so high energy actually has the reverse effect.

5. As I said previously (pardon me for repeating it) - in a given cartridge a bullet/load combination yielding the highest momentum (high-SD bullet @ moderate velocity) will always perform better than the highest energy combination (low-SD bullet @ high velocity). High induced energy levels becomes self destructive on Softs and are so destined for those bullets that can take the "abuse".

6. You mentioned that you would not dream of using a the 175 gr Barnes-X as it would not stabilize. My experience tells me a different story. Firstly, the retrieved bullets in my wetpack test was found straight ahead with their mushroom pointing to the backstop. Unstable bullets normally tumble. Secondly, in big game such as kudu they go straight through on angled shots and none has been found so far. Thirdly, I have modeled it on WINGYRO (it is a program that calculates the gyroscopic stability of spin-stabilized projectiles) using the following statistics, having measured the bullet myself:

Bullet Length = 37.5 mm or 1.476"
Nose length = .571"
Specific gravity of material = 8.93
Twist rate = 1 in 8.66" (being the standard)
Stability Factor (SF) = 1.19 from as low as 2,100 fps
For stability in air we require SF = 1.0

Even though we do not seem to see eye to eye, the discussion has been an interesting one so far and I hope the readers have enjoyed it.

Chris.

Posting for Chris Bekker:

Trajectories:

Gerard,

Gerard you have cheated. You must have used a blunt nose for the 7 x 57 and a spitzer for the 7 mm STW. The 175 gr Barnes-X bullet has a BC of .521 and that is what you should have used. Even the Nosler Partition has a BC of .519. I used Quick Target to model the trajectory and wind deflection of the Barnes-X bullet at 15 mpu and a MV of 2,350 fps to restate your figures. Since you are working with imperial units I assumed the distance is also in yards. The result I got is shown under (a) and for ease of reference I will show your figures under (b) and (c) :

Cartridge --------- Mass -- Path @ 100 - Path @ 300 - Wind Drift @ 200 - TOF @ 200
a) 7 x 57 mm --- 175 gr ----- +3.60" -------- -11.70" ------------- 5.10" ---------- 0.2745 sec
b) 7 x 57 mm --- 175 gr ----- +4.38" -------- -18.54" ------------ 12.45" --------- 0.3264 sec

c) 7 mm STW -- 120 gr ----- +0.78" ---------- -4.02" ------------- -1.70" --------- 0.1769 sec

I did not check the statistics of the 120 gr bullet as the BC is not known to me and will assume it is correct. Trajectories and wind deflection are solely determined by BC and the launched velocity (MV). Sure an additional 1,500 fps in favour of the bullet used in the 7 mm STW will make up for the lower BC of the lighter bullet and still show a flatter trajectory as well as less wind deflection, but I did not expect you would cheat so openly. Using a heavy bullet at 300 yards at low velocity also goes against common sense, but for the sake of making an academic (theoretical) point it is fine.

Chris

Your points in order:

1. File under excuses for mistakes made.

2. You stand by your conviction that more energy does not result in a larger wound channel volume. So a 300 Win Mag will not shoot a bigger hole in something than a 308 Win. A wound channel from a 7mm RUM will be the same size as the one from a 7x57. What can I say. Go ahead and believe it.

3. I do not understand the statemnt but get a vague feeling that you admit to little experience under actual hunting situations.

4. Where on earth did you get this one from? The entire thrust of my replies to you have always been to forget about Sd and consider momentum, Mo/XSA and bullet construction. When I mention in passing that the role of Ke is in relation to wound channel volume, suddenly you make as if I am a proponent of energy kills. Read my lips: If two bullets of equal momentum and equal construction have differing enrgy levels, the one with more energy will kill more effectively. If you beleive anything else, I have to ask how much actual hunting you have done and I exclude the stalking of wetpacks, building material and other inanimate objects.

5. You repeat your belief that a 30-30 with a 170gr bullet is more lethal than a 308Win with a
150gr bullet. I do not know how you are going to get out of that hole.

6. In WinGyro, in the Display Results window, look at the right hand column. The heading states: Twist in inches/turn for SF=1.5. Any idea why it is 1.5? Your SF 1.19 is woefully inadequate for general hunting to 500m and you will experience many failures through bullets that tumble and turn. You just havn't shot that many yet. Two swallows doth not a summer make. Here is a clue: We have never made a monometal bullet heavier than 160gr in 7mm and that was the old HP range. In HV the maximum is 130gr and that bullet is the same length as a Sierra 175gr BT. Barnes do not make a TSX or a XLC in longer than 160gr. I will put money on it that the 175gr X bullet is on thin ice as well. You better buy a bunch before they are also discontinued.

You say I cheated. Did you miss my first paragraph where I said: "I would also not use a 175gr monometallic bullet in a 7x57 as it will not stabilise sufficiently for decent terminal performance. The 175gr bullet in the comparison will have to be a bimetal bullet of some sort."?

Pay attention Chris, you waste a lot of time when you go riding off in several directions all at once. Does it matter whether the heavy bullet loses by a country mile or a city mile? It loses by a huge margin either way and whining about it will not change anything.

This reminds me of the time around 1991 when a novice hunter bought a 7x57 from me. A couple of weeks later he phoned me in anger and asked why I sold him a rifle that he cannot shoot kudu with. Apparently he tried to book a hunt with an outfit in the Eastern Cape and was told that the 7mm is not allowed. Minimum caliber at their place was .30, the farmer said. I got the number and called them pretending to book a hunt. I mentioned that I have a 7mm RM (I lied) and was told that it will not be sufficient. I said ok, I also have a 30-30 (I lied again) and the farmer was happy with that and wanted to book the hunt for me. I take it you know the guy or have at least conversed with him about these theories on slow heavy bullets.

Posting for Chris Bekker:

Gerard,

This was the poorest response I have received from you so far and I detect your dissatisfaction the way the thread is going for you. The way you conduct this discussion won't further our discussion and is beginning to show its futility.

When I tried to keep the momentum values the same in the scenario I have given you, you accused me of pitching it at too low a velocity and said ... "I would not dream of shooting a 120gr bullet from a 7STW at 3427fps" Then you said ... "So let us redo your table with real life values:

-- Cartridge --/ Mass / Velocity / Momentum / Energy
7 x 57 mm --- 175 gr -- 2,350 fps -- 58.75 --- 2,146
7 mm STW -- 120 gr -- 3,850 fps -- 66.00 --- 3,951"

You deliberately increased both the momentum value of the 7 mm STW after I stated clearly that I wanted to keep it the same for the sake of a fair test! I find this quite amazing that you always veer off. I wanted to see that energy directly relates to the size of the cavity and particularly that flesh differs from homogenous mediums. Now you accuse me of a lack of hunting experience (jumping to conclusions). The point is even if the initial part ( a few inches) of the temporay cavity is bigger due to higher energy (like a splash in water), it does not really help the killing mehanism farther down where the vitals are. The permanent cavity is more closely linked to kill animals more effectively.

In the latest Man Magnum Ganyana describes where he followed up on a buffalo that took a solid bullet through both lungs from .375 H&H and it was still in full flight 12 hours later. Experience has shown that the .375 Rhino bullet that expands to 2.4 times drops buffalos much more effectively. This is not speculation, it is a fact and you can debate this with Ganyana or Katte Katzke if you so wish. I wish to quote Ganyana when he wrote about "Frontal Shots on Buffalo" where he made the point that even if the heart of a buffalo is punctured with a conventional round nose FMJ it leaves a small hole which is invariably sealed as the heart begins to contract to pump the blood and he has seen it to run another 5 kilometers and when you later find them they are dead. Ganyana also mentions another interesting observation ... that his 9.3 x 62 mm with RWS Tug bullets, which expands well, is highly effective on buffalo as the expanding bullet will tore a hole through the heart that is too big to be sealed ... the bigger the hole, the more quickly the animal will collapse. He also confirms, from his experience the effectiveness of the dual-diameter monolithic solids that have cutting shoulders ... in fact in .366 calibre bullets (9.3 x 62 mm) they leave a bigger permanent wound channel than a .500 calibre bullet in round nose FMJ with a smooth surface. We also know that a solid with a broad flat meplat cuts a wound channel that is unlikely to seal and works better than a round nose solid despite the same energy. We have to recogonise these facts. Then the cherry on the cake ... the 380 gr .375 Rhino bullet opens up to 27 mm and cuts a huge hole through the hart with its 4 sharp petals and is also more effective than a soft that mushrooms in a ball like appearance with smooth edges. See the attached picture of a retrieved 400 gr .416 Rhino bullet.

Here Katte sits with Jack Krieger of Krieger barrels fame with a buffalo with an unusually big boss.



The phrase that you composed, after you have cheated was most hilarious Boet, and I am going to repeat it here just to enjoy it one more time ..."Does it matter whether the heavy bullet loses by a country mile or a city mile?" Gerard, it does matter because Cape Town is farther away from Johannesburg than Bloemfontein. Your comparison was willfully skewed and you thought I would not notice. If you want to do comparisons out to 300 yards, we should at least compare two Spizers with each other, and not slip a blunt nose in and then don't state the BC's. Also trajectories were never the point of discussion - we were talking about cavities caused by energy, but you veered off.

I have given you the proof that the 175 gr Barnes-X bullet is doing a fine job on big animals even at low velocity with a stability factor of 1.19 even though it is somewhat lower than the generally accepted 1.3 to 1.5 level. I do want to make a promise to you that I won't hunt at 500 yards with this load as anyone who attempts that must be an imbecile. The 7 x 57 is my bushveld rifle and I use my 300 H&H for longer ranges out to 350 yards. I further undertake not to use my 300 H&H at a 1,000 yards, I will leave that to the benchrest crew. Concentrate on the real issue ... we were talking about doing tests in wetpacks, and it worked fine in my tests, but you veered off to stabilization issues to create confusion.

I guess this brings our discussion to an end then.
Take care and happy hunting.
Chris