Hollow point ammo... And why heavier are more consistent

So your here now zombie?


We have shown in the other thread... where I actually had time to flesh things out better than this thread... and also others.

That you are the one misinterpreting the math and laws of physics.

You said many things that just don't jive with the laws of motion...Your zero force statement was just... wrong...

You haven't posted in that thread in a while, more was added, you should go look at it. There are more experiment results as well.


I have talked to people on this face to face, all good minds with a firm grasp of these things... all agree that momentum is key to penetration.

You seem intelligent, this isn't a bash on you, just a statement that you are incorrect.


You bash looking at results and then trying to give reasons to why the result happened... you say that isn't how science works.


You realize that the laws of motion, gravity, evolution, and many others all got their start from this process, and were later refined with controlled testing.


As I explained in the other thread, energy determines the cavity left by the bullet that is larger than the bullet diameter. Higher energy gives a larger cavity

But momentum determines the penetration depth.

Go to the other thread to see the math and explanations.



Also... I can honestly say, I have never received an F on an exam. :p
 
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marine6680 said:
... you are the one misinterpreting the math and laws of physics. ...
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Possible, but I don't think that's been demonstrated. I sort of lost interest once Ed Ashby's report was mentioned, as that's when I knew that a serious discussion was probably impossible. I mean that without any intent to insult, BTW.

marine6680 said:
There are more experiment results as well.
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I shouldn't have to explain what was pretty obviously wrong with the "potato and nail" experiment.

marine6680 said:
I have talked to people on this face to face, all good minds with a firm grasp of these things... all agree that momentum is key to penetration.

You seem intelligent, this isn't a bash on you, just a statement that you are incorrect.
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I appreciate the spirit in which those comments are offered.

I'd offer in return that I would be wrong if we were talking about penetration through fluid structures (where drag is a very big deal) or the penetration of shafts (like nails, or arrows) which experience increases in drag during penetration ... or penetration into inelastic solids with near zero plastic ranges (like a potato, lol).

Perhaps my mistake is in assuming that we are talking about the penetration of projectiles (i.e. "pellets" or "missiles" as commonly referenced in ballistics literature) into elastic solids with a wide plastic range. In such structures (muscle as an example) drag is a fairly insignificant factor.

marine6680 said:
You bash looking at results and then trying to give reasons to why the result happened... you say that isn't how science works.
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Well, that's either a partial misrepresentation on your part or a failure to communicate well on mine. The test of a good hypothesis is not whether it matches a small subset of observed phenomena, but rather whether it can predict the results.

That's the problem with the formulas offered by Hatcher and Taylor for instance ... they came up with mathematical models which seemed to describe the observed behavior, but failed when the variables went beyond a very narrow range of values. Bad math, horrible physics ... yet some people still insist they were/are correct. Its' somewhat indicative that they also consider(ed) momentum a big deal.

As a metric, momentum doesn't tell you much of a predicative nature, which is another clue.

marine6680 said:
You realize that the laws of motion, gravity ... got their start from this process, and were later refined with controlled testing.
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I am purposefully leaving out "evolution and many others" because it invites a lot of off-topic discussion which is unnecessary. The laws of motion were actually derived almost from pure philosophy, and confirmed by testing. The proof of their validity is their ability to accurately predict almost any (non-relativistic) physical phenomena involving inertia, action/reaction, acceleration, etc.

This predicative quality is key to any valid scientific explanation, as it directly invokes the principle of universal physical principles.

This conversation is at a point where it holds little practical value. If people simply choose duty-rated ammo in a common duty caliber, the differences in terminal ballistic performance will be nearly insignificant. However poorly someone reasons out the cause of those differences ... not an argument which holds my interest. Nobody is likely to get killed because they misunderstand the physics of this problem.

I am content to get paid to to scientific measurement for a living and leave it at that. I don't need anything more than that, the physics themselves and the fact the stuff I do "works" (both in the lab and in practice) to be content, and it's not worth by getting snippy (or snippier, lol) over it.
 
I will say zombie... You are easier to discuss with than many on the internet.

I would say that I believe that at handgun velocities, test gel is a semi solid that reacts like a fluid on impact. So describing the math in relation to fluid dynamics and particle motion through said fluid is the way to go.

You mentioned a study and some people that were brought up and made you step back from the topic... In all honesty, this discussion was the first I had heard of them...

I tried reading the linked study, and didn't make it far. I am unsure when it was done, but the lack of SI units and the mixing of so many other unit types, it hurt my head a bit.

This has gotten into less practical and into the pure physics behind it all.

For me, it's just good fun, I win, I lose, I learn, I teach... I just enjoy talking about the underlying rules and laws of the universe. Heck I even dabble in philosophy and psychology too.


This has provided more entertainment and enjoyment than most TV for a while, so I found it far from pointless.
 
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I will say zombie... You are easier to discuss with than many on the internet.
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I try, lol.

... at handgun velocities, test gel is a semi solid that reacts like a fluid on impact. So describing the math in relation to fluid dynamics and particle motion through said fluid is the way to go.
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Ballistic gel is actually a "colloid", and specifically fluid microscopically dispersed within a solid. The properties exhibited are those of an elastic solid with a fairly wide plastic range.

In a strictly fluid medium, drag is a very big deal, and therefore momentum is as well. In a elastic solid (like gel, skin, bone or muscle), shearing resistance is the thing you are concerned with, and drag has very little to do with the problem, unless the penetrating object accumulates drag (like a spike or the shaft of an arrow). Shearing resistance does NOT increase with velocity in this type of medium. It actually decreases in elastic mediums. That's why KE is the big deal for these kinds of problems.

This has provided more entertainment and enjoyment than most TV for a while, so I found it far from pointless.
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If I can make a suggestion, noodle away on the "potato experiment" for awhile. If you happen upon the "grand aha" which demonstrates it to be a worthless example, you'll amuse yourself to no end ... discovery is fun.

You'll also find it interesting to note that the "Taylor Knockout Formula" is being actively defended by some in another thread: LINK ... nonsense dies hard when people want to believe something which makes them comfortable with their assumptions, preferences or prejudices.
 
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zombietactics said:
In a strictly fluid medium, drag is a very big deal, and therefore momentum is as well. In a elastic solid (like gel or muscle), shearing resistance is the thing you are concerned with, and drag has very little to do with the problem, unless the penetrating object accumulates drag (like a spike or the shaft of an arrow). Shearing resistance does NOT increase with velocity in this type of medium. It actually decreases in elastic mediums. That's why KE is the big deal for these kinds of problems.
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The fascinating part to me is that we got through 5 pages of the other thread with no explanation from you except the logical fallacy of "I am an expert, trust me." Only now, in this thread, do you offer any sort of explanation regarding your contention that KE matters more than momentum.

However, it seems to me that the statement quoted above is the opposite of your previous statement:

zombietactics said:
Well, there are lots of simple experiments from which you'll derive the same results. One of my favorites is dropping two weights (heavier vs. lighter) on top of nails from varying distances to see how far the nail is driven (or 'penetrates')

Amazingly, it is always identical KE which produces identical penetration.

I'd like to see the experiments demonstrating the opposing hypothesis, or at least falsifying this one.
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Unless you have nails that have wider tips than bodies, they are "accumulating drag" and they are certainly closer to spears and arrows. Wood may be consider "elastic" but it is no where near on the same level as muscle/flash.

zombietactics said:
demonstrates it to be a worthless example,
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For my "worthless" potato experiment, would you prefer that I drop heavy and light weights on the nail to drive it into the potato? I can do that, but that's not how bullets (or spears or arrows) work.
 
But how do we know if our experiments in the lab translate into the real world?
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Dr. Fackler has stated that the street/field/battlefield are the ultimate laboratories.

The lab people like to dismiss anything that they cannot quantify in the lab. You are missing half the answer if you do it that way.
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Care to provide examples?
 
Brian Pfleuger said:
The fascinating part to me is that we got through 5 pages of the other thread with no explanation from you except the logical fallacy of "I am an expert, trust me."
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That's - strictly speaking - not true. I've done quite a bit more than simply making an empty claim to expertise, or "argumentum ad verecundiam".

I'm not trying to pull rank, but let's be candid here ... how far would you get into a discussion of pizza, or the restaurant business in general, before mentioning that you actually operate a pizza place ... if people with no particular experience were posting up what you saw as raw conjecture or incorrect information?

Brian Pfleuger said:
Unless you have nails that have wider tips than bodies, they are "accumulating drag" and they are certainly closer to spears and arrows. Wood may be consider "elastic" but it is no where near on the same level as muscle/flash.
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Yep ... I gave a bad example which relates to a different test case altogether. My fault for muddying the waters.

Brian Pfleuger said:
... For my "worthless" potato experiment ...
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I think if you stew on it a bit, you'll come to a certain realization about how you set that up. It's better for you to discover it on your own, than for me to wade further into "being a pedantic jerk" territory. ;)

I find encouraging that you and I agree on Taylor's Knockout Formula being total nonsense ... because it (without any real doubt) is nonsense.
 
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For the potato thing... It's not really a fluid.

It may fit more into the elastic solid definition better. I may puzzle over it some... Though, it may either elude or be so obvious that I would smack myself at its discovery... We will see perhaps.



You are right about the makeup of ballistics gel.


Though I think it crosses the threshold of elastic solid to semisolid.

I am sure there is a quantifiable way to distinguish between the two though, but I am not immediately familiar with it.


There is definite sheer within the gel, that is evident from the tearing exhibited in the "wound cavity". The bullet is exceeding the limits of that, causing a failure of the structure, it does not self heal with time.

Though I think it also acts in very fluid like ways as well. BB calibrations look like the material flowed around the BB more than ripped/sheared apart.


I think we have reached the point where...

If the gel behaves like a liquid or has liquid like properties when a bullet is fired into it, then momentum is the ruling factor.

If it is only an elastic solid, then energy is the ruling factor.



It is also quite possible the answer lies in between those... The gel acts like a little of both, in a bit of a grey area of not fitting well onto either definition neatly.

That would mean that both measures factor in, and maybe why it confounds the issue and causing these debates.


Edit: new replies I have not read before posting this... Must go look.
 
Duncan MacPherson, who wrote the book "Bullet Penetration: Modeling the Dynamics and the Incapacitation Resulting from Wound Trauma" (see - http://pw2.netcom.com/~dmacp/ ), describes properly prepared and calibrated ordnance gelatin as a "soft solid".

In a elastic solid (like gel, skin, bone or muscle), shearing resistance is the thing you are concerned with...
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Except for bone, MacPherson has identified Inertial Force as the primary force involved, with Shear Force playing a much lesser role, becoming important only as the bullet has substantially slowed down. See - http://www.firearmstactical.com/tacticalbriefs/2006/04/03/0604-03a.htm (Scroll about 2/3 down the web page to the section titled: "Extract from 'Wound Ballistics Misconceptions.' (Duncan MacPherson, Wound Ballistics Review, 2(3): 1996; 42-43)".
 
zombietactics said:
"being a pedantic jerk"
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Pedantic is my favorite word.;)

I find this subject to be very interesting... literally sleep disturbingly... interesting.

The more I have considered it, the more I believe that we are both simplifying it beyond a useful level.

For instance, considering a bullet... once it has entered the flesh, the friction is a fixed (for simplicity) vector, directly opposite the momentum vector. Friction is the only "thing" countering the momentum.

Kinetic energy is "work" energy and is used to do all work. This includes expanding the bullet and pushing flesh out of the way (essentially perpendicular to the momentum vector).

That means that it is not kinetic energy OR momentum that are responsible for penetration, it is both.

Since kinetic energy can not be changed without changing the momentum and neither can momentum be changed without changing the KE, "using up" (decreasing) one of them also uses up the other. They are, in fact, both being decreased, simultaneously and constantly, by the forces that are decreasing the other.

This also means that a larger diameter bullet with the same momentum as a small diameter bullet would require more kinetic energy if it were to penetrate the same distance, as it has to do more work to move a greater amount of flesh.

That larger diameter bullet can be heavier and moving slower or it could be lighter and moving faster. If it is lighter but moving faster, it is also shorter. If it is shorter, the friction vector countering the momentum will be smaller but the amount of work by the kinetic energy done to move the flesh will be larger, relative to time.

It is "better" to make the bullet heavier by making it longer rather than wider because only the friction on the outer surface of a cylinder counters the momentum while if it is made wider, the amount area counteracting the KE is proportional to the area of a circle. (This is essentially Sectional Density).
 
At least I am not the only one who loses sleep due to late night musings.


We may be over simplifying things, sometimes it helps to do so to convey the basic idea to other, some who know little on the subject.



But yes energy and momentum are linked, one can not be gained or lost without the other. The main argument is which is the primary player in penetration.

The answer may not be simple, changes in the different factors may change which is the primary driving factor

For 9mm bullets, momentum may drive... For the best .357 loads, energy may take over.


To really know, we would need to do much much testing in as controlled and precise ways available.

I doubt any of us has the time, money, or materials needed.


But we can still argue on the internet. :D
 
I'm being lazy ...

So someone please calculate the momentum of a 230gr .45ACP round traveling ~850fps ... and then the KE.

And then calculate the momentum of a 5.56 62gr m8555 spitting pure hate at ~3000fps ... and then the KE.

Using SI would be helpful.

I'll get to it eventually if nobody else does.
 
Care to provide examples?
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The 115 grain JHP +P+ 9mm and the 125 grain 357 magnum are both phenomenally successful in real world shootings but fail to penetrate to the desired depth in gelatin based upon an arbitrary baseline.
 
The 115 grain JHP +P+ 9mm and the 125 grain 357 magnum are both phenomenally successful in real world shootings but fail to penetrate to the desired depth in gelatin based upon an arbitrary baseline.
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And let's review your previous statement...

The lab people like to dismiss anything that they cannot quantify in the lab. You are missing half the answer if you do it that way.
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So what are "the lab people" dismissing?
 
Is it arbitrary...

I wouldn't say that, it was based on many factors. It is the best criteria available to quantify several factors of good ammunition performance.

Perfect? No.


The examples you provide are just the exceptions that test the rule.

Outliers always exist within data.
 
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