What is the optimal penetration depth for the 5.56/.223 round?

What EXACTLY does penetration depth mean?  (I think it means how deep does it penetrate before starting to fragment).

Is the "optimal" depth the same for all calibers?

Who came up with this number?

How did they obtain this magic number?

(Edited for spelling error)

12-18 inches, has to do with distance it takes to reach the vitals of a human being from odd angles.



No, has nuthin to do w/ fragmentation.


Yes, for self-defense purposes if it won't reach past 12" pick another round/type.



Mike

No way, optimal is 4-6".  With 12"+, it would go right thru an average person.  Even with Santa's belly, a frontal entry after 12-16" would be exit behind him.  Your typical heart, lungs, spleen, liver are all reachable within 2-4" of your chest from the front.  Only a shot from the side would travel the longest but you have the arms and ribs to deal with first.

Sorry Hail Mary your post is [BS]

See here: [url]http://greent.com/40Page/general/fbitest.htm[/url]

exerpt:
[b]FBI Ballistic Test Protocol:[/b]
Briefly, the performance standards are simple. A handgun bullet [b][red]must consistently penetrate a minimum of 12 inches of tissue in order to reliably penetrate vital organs within the human target regardless of the angle of impact or intervening obstacles such as arms, clothing, glass, etc. Penetration of 18 inches is even better[/red][/b]. Given minimum penetration, the only means of increasing wound effectiveness is to make the hole bigger. This increases the amount of vital tissue damaged, increases the chance of damaging vital tissue with a marginally placed shot, and increases the potential for quicker blood loss. This is important because, with the single exception of damaging the central nervous system, the only way to force incapacitation upon an unwilling adversary is to cause enough blood loss to starve the brain of its oxygen and/or drop blood pressure to zero. This takes time, and the faster hemorrhage can occur the better.

Believe they know "a bit" more than you do about this subject.

Mike

Thanks, Mr. Wilson.  I didn't even feel like touching that this morning.

Yep, 12-18" is considered ideal. Less penetration may mean shots that must enter the body from an odd angle (not straight into the chest frontal shots) will lack sufficient penetration to reach the vitals. This also applies in cases where a person may have an arm/s raised up at chest level (like when they are pointing a weapon at you). If your bullet must pass through that arm, it still needs to be capable of reaching the vitals. This is where lightweight varmint ammo sometimes comes up short and why it should be avoided for self-defense.



Penetration depth is how far the bullet penetrates before coming to a rest. You are thinking of the "neck", which is the distance penetrated before fragmentation begins.  



Yep. It applies to the 9mm, .40, .45, 12 gauge, .223, .308 or any other caliber used for self defense.



The FBI after learning some tragic lessons following a 1986 shoot-out in Miami, FL.



It isn't so much magic as it is practical. If you have a bullet that is capable of penetrating to a depth of 12-18", you have a better chance of reaching deep vital organs and blood vessels. Just as Dr. Gary Roberts told me in a post this morning, you don't choose ammo for best case scenarios, but rather the worst. In most cases 8-9" of penetration may be all that's needed to be effective. But there will be situations where it will not be enough. Again, these are angled (profile) shots where the bullet may have to pass through the upper arm and traverse the chest cavity before reaching the heart, major blood vessels or the spine. The bigger the person, the more difficult. Bones only add to the problem. So while in most cases less penetration is good enough, it's a good idea to have a round that will penetrate deep enough no matter the circumstances. You can't always pick your shot.

-Charging Handle

This is singling out handgun ammo.  It expands, not fragments.  So saying it should penetrate 12" makes sence.  But when talking about 5.56/.223 I still thought "optimal penetration depth" refers to how far it goes BEFORE fragmenting, not entirely how far it will go.  Hey, I could be wrong, I'm not an "ammo geek".

Thanks for clearing that up.  So, now I have ANOTHER question (you knew this was coming).  What is the optimal "neck" for 5.56 self defense rounds?

Yes it is singling out handgun ammo, but the same is true for all rounds.

You use handguns for the same reason you use shotguns or rifles - to reliably stop the aggressor.  Distances to the vitals don't change based on the weapon used.


NO!  As mentioned above that is often reffered to as the 'neck'.  You want the neck to be as short as possible.

You are only kidding right? If this was sarcasm you need to insert one of those little smilies after your message like this..... [:D].



I have read that the average thickness of the adult human torso is 9". So in many head on frontal shots, the "adequate bullet" may exit the body. But in doing so it is robbed of much of it's momentum. As light as the .223 is to begin with, and if the bullet is a fragmenting one, whatever exited the body would not pose a tremendous risk to others anyway.



Ok. But what do you do if you have to make a shot like this and you have a round only capable of penetrating 4-6"? Heck, a round only capable of penetrating 4-6" may lose most of it's effectiveness while passing through the arm of the badguy as his arms are at chest level while pointing a gun toward you! This is why the experts recommend against varmint bullets and birdshot for home defense. Don't choose ammo for the best cases scenarios, choose for the worst. With that said, why choose a load that will only penetrate deep enough in some situations when you can have one that will in nearly all situations?

-Charging Handle

Believe according to the "Ammo Faq", tacked to the top of the Ammunition Forum here: [url]www.ammo-oracle.com[/url]

The new BH 100grn. mag length bullet might be optimal (based on the shown gelatin test), but for certain brouhaha is the best to answer this question...

M193 is NO slouch in this reguard.

Mike

For 223, read here: [url]http://www.olyarms.com/223cqb.html[/url]

Seems a pretty good article,
Mike

That could vary. For the heavier match loads such as the 75/77 gr, a neck of 1.5" is pretty good. However a neck that short with a 55 gr M193 bullet may not be so ideal. It's really rather bullet specific.

-Charging Handle  

You pretty much have it! If you have a fragmenting bullet that yaws early, fragments violently (and early), and the fragments continue penetrating out to at least 12" (14" might be even better), then you likely have a very good round. In fact, that description screams BLACK HILLS 77 gr NOSLER NATO PRESSURE AMMUNITION! And for soft points, you are looking for the same general thing, which is at least 12" of penetration in gel/tissue and robust expansion. Some softpoint .223 loads like the 64 gr powerpoint may also have a tendency to fragment somewhat as well. Others such as the bonded TBBC may retain nearly all of their weight but still expand very nicely.



That's what Tatja and Brou say and that's good enough for me! Haha. But seriously, a good fragmenting bullet creates a larger wound channel than a softpoint and that's why it's favored by them.

-Charging Handle

Even though the article is geared towards handguns, I think it gives the most concise summary of the 12" rule and other important factors: [url=http://www.btammolabs.com/fackler/ideal_police_bullet.pdf]The ideal police bullet[/url]

You can then read the other articles in the thread I have tacked under [url=http://www.ar15.com/forums/topic.html?b=3&f=16&t=164814]Wound ballistics information - Articles by Dr. Fackler[/url] tom compare the specific performance of M193 and SS109 to the criteria set forth above.

You can also refer to [url=http://www.btammolabs.com/fackler/effects_of_small_arms.pdf]Effects of small arms to the Human Body[/url], which has comparative thicknesses of the thigh and torso overlayed on the bullet's permanent cavities.

Thanks everybody.  Great info.  Thank god I'm not confused about the neck/penetration issue any longer.

Mike,

Be aware (C_H will have deja vu) that the OAI version of Taubert's article has been heavily edited.

[grammah]

As always I suggest people interested in fragmentation start with [url=http://www.ammo-oracle.com/#m193orm855]The AR15.com Ammo-Oracle section on fragmentation and terminal performance.[/url]

There are two basic ways (and perhaps the ONLY two ways) to incapacitate an aggressor.

You can deny the muscles signals from the brain.

You can deny the brain oxygen.

In ballistics the best way to accomplish these are:

1.  A direct CNS hit that does enough damage to cause instant loss of motor control or consciousness.  This basically means the head or the spine.

2.  A hit causing sufficient vascular damage to cause the individual to "bleed out" quickly enough to get them out of the fight via hypoxia before they can do anyone damage.

1. is pretty hard to do consistently and bad-guys don't usually cooperate.  (The nerve core in your spine is about the width of your pinky- sure, Clint Eastwood shoots the rope that his partner is hanging from in The Good, The Bad, The Ugly, but he's a better shot than you.  Also, he probably is better looking too!).

2. is easier, but still difficult and is FAR more dependent on bullet performance than 1.

Given this, the best rounds are those that, whatever else they might do, will inflict severe vascular damage.  Since almost all penetrating projectiles (regardless of performance) will destroy CNS structure they come into contact with we don't really bother evaluating this.  We aren't worried about the rounds that end up perfectly placed since even an ice pick would do the job if perfectly placed.  We worry about the rounds that, given the practical nastiness of a gunfight, aren't perfect headshots.  These rounds have to incapacitate also.

This means they have to:

A.  Get deep enough to reach major vascular structures even if they have to pass through an arm, thick clothing, a leg, etc before they encounter important vascular structures.  The average human torso is 9 inches deep front to back.  Minor vascular structures bleed, but not fast enough to be an issue.  We can't wait that long.  Major structures start 3-5" under the skin, except in the extremities.

B.  Do as much damage to as many of them as possible to increase the speed of hemoraging.  Bear in mind also that even if the heart is utterly destroyed the brain contains enough oxygen to continue major functions for 10-15 seconds.

It takes about 1 liter of blood loss to induce shock in most individuals.  2.5 liters of blood loss is generally fatal.  Cutting major vessels can result in as much as a liter and a half per minute.  45 seconds, however, is still a long time for someone to keep fighting.  Cutting a few major vessels is better, obviously.  Leaving a pair of holes for the blood to clear out of is also helpful.  (This is why I actually believe rounds should exit).

Fragmentation is important in .223 / 5.56 rounds because they don't make very big holes without it.  With it, they are devastating.  (Look at some of the gel pics).

Ideally then you want something that penetrates deep and does a lot of damage after about 3" of penetration.

Clearly, the "neck" (or the distance before the round yaws and begins to break up) must be inside of 3" or so to increase the chance of doing vascular damage.  You also don't want yaw to start to late in case you are shooting at a Heroin addict and his torso is actually only 5" deep.  (By the way, ALL pointed bullets yaw.  Not all fragment).

Also, projectile penetration (both handgun AND rifle) should exceed 12" to make sure that sufficient penetration to pass through extremities and still do major vascular damage exists.

Right now the best rounds I know about for these purposes are the 100 grain OTM round we tested and the 77 Nosler NATO round we tested.  ([url=http://www.ar15.com/forums/topic.html?b=3&f=16&t=167591]77 Grain Testing here[/url] and [url=http://www.ar15.com/forums/topic.html?b=3&f=16&t=145122]100 Grain Testing here[/url]).

Both of these have very short necks (under 2") and LOTS of fragmentation.  They make big and deep holes.

The 100 grain OTM basically yaws IMMEDIATELY.  It's problem is that bullet drop is huge after 150 meters or so.

The 77 grain Nosler has a longer neck, and slightly less fragmentation (there is just less lead to fragment) but is still an outstanding distance performer.

Now, if you don't want to go to the 77 grain Nosler (they are quite pricy) you might want to think about the 68 or 69 grain SMK rounds or plain ole M193.

All of these typically penetrate 12" and fragment nicely.

Feel free to post any other questions, but take a look at the [url=http://www.ammo-oracle.com/]AR15.com Ammo-Oracle[/url] too.

If I may be so bold, it appears that ALL OTM bullets will fragment once you get in the 68gr and heavier range at reasonable velocities. Not all have been tested, but it stands to reason that the jacket thickness is not able to withstand the forces exerted when the bullet begins to yaw. The Nosler 77 OTM is obviously a very good performer, but even a 68/69gr SMK is a bullet that I wouldn't want to be shot with personally.