Talked Guns in College Class Today: Diameter and penetration

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bratch

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These are some quotes from my lecture today. Thought you guys mught find them interesting.

"diameter: Not critical if the diameter is greater than 0.25 in"

"Greater penetration can be achieved by sacrificing hole diameter as maximum penetration appears important. Under normal conditions, hole size may prevail because of the difficulties in removing debris in small-diameter perforations"

"This is the distance the bullet must travel before encountering the target . Excessive distance with any gun can result in:
Inadequate penetration
Inadequate hole size
Irregularly shaped or ‘keyed’ holes"

This is a photo that was included in my professor's presentation.
 

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I've always thought of effectiveness as maximum damage, not necessarily penetration.
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Remember that the quotes above were taken out of their context, so it's impossible to know exactly what he was "advocating", or even if he was advocating any particular position (versus explaining the various factors and hypotheses). In any event, "maximum damage" to non-vital structures will not incapacitate a target. Penetration is needed to ensure that whatever damage is done affects vital structures. A small hole in a vital structure is far more effective than a big hole in a non-vital structure. Of course, like anything else, it's possible to have too much of a good thing, but given the choice I will take over-penetration over under-penetration any day.
 
Not sure how much I believe him, taking just the quotes provided. For mortality I was under the impression that maximizing the amount of energy that's transmitted into your target is more important than penetrating. When you think about it, the human body isn't really all that deep when viewed from the front.

Just how little penetration is "under" penetration?
 
bratch's professor is correct

I've always thought of effectiveness as maximum damage, not necessarily penetration.
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You thought wrong.
I was under the impression that maximizing the amount of energy that's transmitted into your target is more important than penetrating.
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Your impression is wrong.

According to the FBI, penetration is more important than anything else when it comes to handgun rounds:

From
http://www.firearmstactical.com/pdf/fbi-hwfe.pdf

The crush mechanism, the result of penetration and permanent cavity, is the only handgun wounding mechanism which damages tissue. To cause significant injuries to a structure within the body using a handgun, the bullet must penetrate the structure.
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The critical wounding components for handgun ammunition, in order of importance, are penetration and permanent cavity. The bullet must penetrate sufficiently to pass through vital organs and be able to do so from less than optimal angles. For example, a shot from the side through an arm must penetrate at least 10-12 inches to pass through the heart. A bullet fired from the front through the abdomen must penetrate about 7 inches in a slender adult just to reach the major blood vessels in the back of the abdominal cavity. Penetration must be sufficiently deep to reach and pass through vital organs, and the permanent cavity must be large enough to maximize tissue destruction and consequent hemorrhaging.
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Bullet selection should be determined based on penetration first, and the unexpanded diameter of the bullet second.
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It is essential to bear in mind that the single most critical factor remains penetration. While penetration up to 18 inches is preferable, a handgun bullet MUST reliably penetrate 12 inches of soft body tissue at a minimum, regardless of whether it expands or not. If the bullet does not reliably penetrate to these depths, it is not an effective bullet for law enforcement use.
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The critical element is penetration. The bullet must pass through the large, blood bearing organs and be of sufficient diameter to promote rapid bleeding. Penetration less than 12 inches is too little, and, in the words of two of the participants in the 1987 Wound Ballistics Workshop, "too little penetration will get you killed." Given desirable and reliable penetration, the only way to increase bullet effectiveness is to increase the severity of the wound by increasing the size of hole made by the bullet. Any bullet which will not penetrate through vital organs from less than optimal angles is not acceptable. Of those that will penetrate, the edge is always with the bigger bullet.
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In what class was this discussed?
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I'll let that cat out of the bag later. I want everyone to have fun with this for a little bit.

Here is another quote

"BHP may impose limitations on some"
 
I stand corrected. So how do they balance the need to penetrate with the risk of cleanly going through the target?
 
...how do they balance the need to penetrate with the risk of cleanly going through the target?
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Are you referring to "over-penetration"?

According to the FBI document, you should not be concerned about "over-penetration."
 
It was actually my Drilling and Completions II class. All of the quotes are regarding perforating oil wells. The picture is of what different drilling fluids can do to perforation performance.

It was probably my coolest single day of class in college. We talked about det cord and shape charges on top of the quotes I posted.
 
All of the development of modern small arms projectiles places emphasis on both expansion and penetration, the sum of which is terminal performance.

To grossly exxagerate the point that neither by itself is effective, we can look at a baseball and a piece of wire. Neither is likely to inflict a fatal wound on a human. A baseball has a very large diameter and creates good blunt trauma, but will certainly not penetrate organs. A .030" wire shoved through the body, even the heart, lacks the diameter to cause lethal levels of bleeding.

Similarly, a .50 caliber bullet that does not penetrate vital organs is no more effective than a .17 caliber bullet that penetrates them but does not cause a substantial permanent wound cavity. But a .400" bullet that both pentrates vitals and expands to over .8" with sharp tearing and cutting edges will do a very good job of interrupting vital functions. There is a happy medium. Penetration is the more important of the two, but expansion is not to be understated. Just ask a returning soldier who emptied his M-4 magazine of non-expanding .224" bullets into an adrenaline-high enemy. Bet he would have preferred something that did a bit more damage. The guys I know wish the .30 caliber was still used. They also prefer a .45 to a 9mm.

If expansion was not a necessary component of terminal performance, the bullet manufacturers would not have spent millions of dollars developing bullets that do so, especially those premium bonded or partitioned bullets.
 
Why do we do this to ourselves?
Over and over, endlessly debate this issue?
I can shoot you through the abdomen with a .50 BMG with 12" of penetration and not kill you.
I can shoot you through the carotid artery with a .22 and half an inch of penetration and you will bleed to death.
 
Well, your class is certainly more informative.

I'm taking a physics class now, wherein the professor (a PhD in physics) declared that on the "really powerful rifles," the bullets go so fast that they burn up in the atmostphere--"just like the space shuttle." I kept my mouth shut.

:banghead:
 
Sounds about like the blasting course I took 20+ years ago. How to design a shot based on the materials to be fractured (data obtained from test holes, many of themn then used as part of the blast grid), timing, and fusing. Also covered was cutting steel bars, columns, pipe, and I-beams with cord or shaped charges, creating shaped charges for penetration, blasting reenfrced concrete structures, etc.
It was a really cool class. The class project was a gravel pit shot.
Another lab was cutting sections of an I-beam sticking out of the ground about 10 feet. Each group of 4 got to chop another foot off the beam using shaped charges.
"Explosive Engineering" by Paul Cooper is a more recent text that covers everything from the chemistry to the basic uses of explosives.
 
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Just ask a returning soldier who emptied his M-4 magazine of non-expanding .224" bullets into an adrenaline-high enemy. Bet he would have preferred something that did a bit more damage. The guys I know wish the .30 caliber was still used. They also prefer a .45 to a 9mm.



Rolls eyes.
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Would you like to know their ranks? Why do you think the military is dropping the 5.56 in favor of the 6.8? Just for the helluvit?


M4? Won't the round fragmentation of the 223 create much more devastating wounds?
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:confused: A FMJ projectile fragmenting in soft tissue? Tumble and yaw, yes, but not fragment.
 
The current military ball 5.56 ammo, M855, is designed to break at the cannelure and fragment when the bullet yaws and attempts to reverse it's orientation once it enters a medium such as flesh. This is easy to duplicate in gelatin or other similar medium. A certain velocity is required and for the moment it escapes me but if memory serves the distance that the rounds will fragment is about 150 meters in the 20" rifle and about 90 meters in the 14.5" M4. The older round, M193, had a longer fragementation range due to it's lighter bullet weight, 55 grains vs. 62. These bullets will even reverse orientation and fragment when shot in water if the velocity is high enough.
 
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