7.62 NATO/.308 "margin of error"

[MachIVshooter]

Any thoughts on why or if a 7.62 NATO/.308 fmj wound (without yawing) would incapacitate more effectively than an identical shot with a 9mm pistol?

Here's my line of thought - the common knowledge is that the rifle will always be better than a pistol (even if the pistol bullet is larger). If the permanent cavity size is smaller with the rifle round and the temporary stretch cavity (fmj bullet, not yawing) has little if any effect on elastic tissues, it seems that there would be very little difference in the resulting wound.

The bolded part is the flaw in your thinking. The permanent cavity isn't just the diameter of the bullet; It is also that of tissue which was stretched beyond it's elastic limits. The higher velocity of the rifle bullet causes much more stretching, and so you end up with larger cavities of both types.

Hangun permanent cavities tend to be only tissue that was directly contacted by the bullet or secondary projectiles due to the low velocity. The hydraulic pressure created by the much higher velocity of the rifle bullet often creates a wound channel much larger than the projectile itself. It is generally accepted that the point at which we begin to witness the hydrostatic shock component resulting in rifle-type wounds is around 2,000 FPS.

 

[Robert101]

The diameter and weight of the bullet is very important. For bullets traveling the same speed, the heavier and larger bullet will inflict more damage. Just ask our current military if the .223 is more effective than a 7.62.

 

[WNTFW]

This video starts at about :40 in after the posters intro.
"9mm vs .45 vs Rifle A Dr's View of Gunshot Wounds"
http://www.youtube.com/watch?v=tku8YI68-JA

34 minutes but a good watch. It is from the perspective of treating the wounded. There are some xray & maybe NSFW.

Pretty sure it was posted on here before.

What I draw from personally is rabbit/bird hunting. Mainly because my sample size was there. Some animals seemed to just drop immediately while others just went on with what I can only describe as more will to live. That is with all inputs on my end of the equation appearing equal. In actuality the inputs probably had way more variance than I thought.

I am sure even if you could quantify all the factors it would a very complicated equation. Plus anecdotal evidence needs to be considered.

 

[riflefan]

As a person who has treated many gunshots over the past 14 years I can tell you it is not a simple question to answer. An individual hit in the heart will almost immediately lose blood pressure and consciousness with death very close behind. A lung shot will immediately drop respiratory capacity by at least 50% and start bleeding, leading very soon to likely respiratory failure. A shot to liver or spleen will result in quick but not immediate loss of blood pressure and consciousness.
Arteries are very tough and elastic and would be difficult to damage with hydrostatic shock, veins not as much but still pretty tough. Muscle can be damaged by shock but the immediate effect is for the muscle to contract and control bleeding, it will later relax and start to ooze. This is the reason some of you may not see a bruise form until the next day. Lung tissue, liver tissue and the spleen are very delicate and can not withstand little if any stretching, nor the kidney.
All in all shot placement with a FMJ should determine the speed of incapacitation. With an expanding round tissue destruction is greatly magnified.
Also with any wound the body can deal with and compensate for a clean smooth wound much better than a jagged or torn edge wound.

 

[ramsfan]

Lung tissue, liver tissue and the spleen are very delicate and can not withstand little if any stretching,

Is the lung tissue easily damaged by temporary cavity stretch?

I have read in other places the lung tissue was fairly resistant to temporary cavity. Is this just a result of less resistance by lung tissue so the temporary cavity dimensions are small?

 

[riflefan]

The lung tissue will not stretch and is very fragile. However, the effect of a temporary cavity will be partly mitigated due to hollowness "air passages" within the lung. It is not a very dense organ. The tissue within that is actually torn will be severely damaged but the area will be a smaller hole because of density.
An example to think of would be to look at highspeed bullet footage. When a bullet is traveling through air it compresses and the area disturbed is small compared to when a bullet hits ballistic gelatin. The denser the media the larger the temporary cavity at a given speed.
I am not very articulate but hope this helps.

 

[ramsfan]

That helps. Thank you.

 

[ramsfan]

Muscle can be damaged by shock but the immediate effect is for the muscle to contract and control bleeding, it will later relax and start to ooze

This will be my final question. Is the muscle damage from the temporary cavity stretch mainly bruising or is there a considerable amount of tearing also?

In general, is the injured area of muscle surrounding the direct bullet path a matter of millimeters or is it several inches?

 

[helotaxi]

This will be my final question. Is the muscle damage from the temporary cavity stretch mainly bruising or is there a considerable amount of tearing also?

In general, is the injured area of muscle surrounding the direct bullet path a matter of millimeters or is it several inches?

As with most things, it depends. The amount of energy transferred to the tissue is what will determine the answer to both of your questions. In the case of a through-and-through from a bullet that either didn't expand, expanded minimally or was traveling very slowly, little energy is transferred and the muscle damage would be mostly bruising and the area fairly localized. This is the primary reason that 9mm FMJ bullets are so ineffective. Minimal damage and the wound channel (both permanent and temporary) is quite small.

 

[riflefan]

As helotaxi said above it all depends. The variable are such a wide spread it is almost impossible to give definite answers. The main principle is bullet speed along with hole size and location all combine to determine outcome. Also there is some variance from one persons anatomy to another. A projectile that hits an artery in one may miss by just enough in another to drasticly change the outcome. If you really want to stop something or someone, the bigger the hole the better.

 

[ramsfan]

To sumamrize what I've learned from this thread.

It is POSSIBLE that a 7.62 NATO FMJ round (M80 ball for example) can pass through the chest and if it misses the heart, spine and any major vessels, the result is a more or less caliber sized wound and the shootee can still be functional. They will not drop like a sack of hammers (unless psychological effects put them down).

It is not very likely because:
>>> Good chance that heart, spine or a major vessel are likely to be hit
>>> Possibility of bullet yawing creating a much larger wound
>>> Good chance the bone will be hit creating a much larger wound
>>> Small possibility of an effect from temporary cavity if it passes very close the the heart or spine

 

[hardluk1]

The temporary wound cavity from a 30cal. from a faster bullet would be larger if nothing but velocity changes. Other than size that is. Thats the difference in the shock wave or hydrostaic shock.

Now change nothing but caliber size again to stay a 50 bmg and parts can and do leave the body do to hudrostatic shock.

Now use a hunting load for the 308, a 125gr ballistic tip at 2800fps and it can turn much of the inside of a 200 lb deer into a liquefied lumpy mess that can pore out when unzipped. Thats where bullet type plays into this game of civilan and military ball bullet types.

 

[Trent]

Ramsfan -

There's enough supporting anecdotal evidence to this to definitely back up your synopsis.

A man at a local gun show in Bloomington IL was shot in the chest by a high velocity 223 round out of a mini-14 a few years ago. He was reported by eye witnesses to be walking around and alert for quite some time before collapsing. (Due to sucking chest wound, he was getting deprived of oxygen as his chest cavity filled with air every breath.)

He was in the hospital 9 days.

But no, it was definitely not "dropping like a sack of potatoes".

Granted, that's a 223 not a 308, but the round went through and through, including a double lung penetration.

There's many other stories out there as well.

308/7.62 NATO is not a guaranteed one shot stop, not even center of mass in the vital cluster.


EDIT: for whatever reason, maybe shock - the man wasn't actually even AWARE that he'd been shot for about 25-30 seconds, according to eyewitnesses. Must have rung his bell pretty damn good for him not to even register it. Something worth considering if you're up against someone who's hell bent on doing you in. They might not even KNOW they are hit until they are, themselves, unconscious.

 

[Shawn Dodson]

 

[ramsfan]

It is easily understandable how/why a 7.62/.308 soft point would immediately put someone down.

I would not expect the same from a FMJ round like the military uses, yet it seems to be the frequently repeated that in combat it puts the target down and they stay down.

I would expect that even a .30 caliber full metal jacket bullet would not have such an effect unless it directly hit a vital structure, hit bone or yawed. The military round (M80 ball for example) could quite possibly pass through a body with only a caliber sized wound and not immediately incapacitate.

If an m855 round zipped right through enemies with only a .22 cal icepick wound, wouldn't M80 ball zip right through with only a .30 cal icepick wound?

It takes multiple m855 through and throughs for a stop but just 1 m80 through and through gets the job done?

 

[rodinal220]

Not unless it has the worlds tiniest proximity fuse

 

[Sam1911]

It takes multiple m855 through and throughs for a stop but just 1 m80 through and through gets the job done?

No, a blanket statement like that is not legitimate. Sometimes it takes more than one hit with the m855 round. Sometimes it takes more than one hit with the 7.62 round. All things being equal. And all things are never equal.

Legend, myth, perception, hype, subjective observation/anecdote, wishful thinking, self-fulfilling enthusiasm, and a tiny sprinkling of raw objective fact all go into our collective understanding of what each cartridge will do.

 

[Robert101]

I understand the desire to discuss lethality of a particular round or bullet. However combat circumstances are constantly changing. Don't rule out the need to penetrate barriers, shoot longer distances. This plays into my selection of why the 308 does have a substantial margin over a 223.

 

[mljdeckard]

There is no guarantee that any given bullet will ever do any particular thing. But with a 7.62 anywhere close to center of mass, I'll call incapacitation or death highly likely in any set of circumstances.