Why Do We Use 5.56 instead of 6.8?

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5.56 is great because it allows you carry a whole lot of bullets. Why is this important? Well, let's look at basic infantry tactics. A squad moves to contact. Then, one fire team lays down a base of suppressive fire while the other manuevers on the enemy in order to close with and destroy their position or to continue suppressive fire while artillery, air, or armor are called in. Having lots and lots of bullets is very helpful in this situation.
5.56 is perfectly lethal and does its job well. It's a relatively flat shooter and easy to hit with between 0 and 300 meters. It does the job. It has killed plenty of Vietnamese, Grenadans, Panamanians, Nicaraguans, Lebanese, Palestinians, Iraqis, Afghans, Pakistanis, Filipinos, etc. Are there better stoppers out there? Sure. Is it as easy to carry 300 rds of them into combat? Nope.
 
I don't need combat experience to discuss what these projectiles will do. I have enough hunting experience to tell me what they will do when they hit a deer or other animal.

I never said a .308 or 6.8mm were magic bullets. But They are better cartridges and will increase the chances of stopping someone when shot.

A magic bullet would be trying to get an unusually small weak cartridge (born from a groundhog/ benchrest cartridge) to do the work of a larger cartridge designed to take down animals that are the size of a man or bigger.

There is no substitute for the impetus of somwhat slower but bigger projectiles.

Animals rarely get psyched when they are shot. They will run if they can. When you see more deer successfully taken when shot by a .308 than are successfully taken when shot by a .223 it's saying something about the cartridges.

Even more puny groundhogs will drag themselves away after getting hit by a 22 centerfire than when they are hit by a .243,25-06 or .308. You can kill a lot more groundhogs with fringe hits from the big high velocity calibers than you will with hyper velocity 22 centerfires.

I would feel a bit ashamed, even inhumane to go hunt whitetail deer with a .223 when I have a .308 in my gun cabinet.

I mean even with the best hunting bullets money can buy it is still a borderline deer cartridge at best.

The 223 biggest advantage is that recoil sensitive people can shoot it without being intimidated. More ammo can be carried.

Even the advantage that it maims more than kills because it stresses the enemies logistics caring for wounded soldiers.

I WOULD trust my life with a .223 in combat.

But why would I if I could get my hands on a 6.8, 308 or a 7.62x39?
 
Ned,
Human beings are NOT whitetail deer and shooting animals has no direct relationship to shooting men.

Even the advantage that it maims more than kills because it stresses the enemies logistics caring for wounded soldiers.
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I really wish people would stop repeating this old tired wives tale. No Army outside of the our Western allies pays anything more then lip service to treating casualties on the battlefield.

Look up the Hall Study which was released by Aberdeen Proving Ground in March of 1952 as BRL Memorandum Report no. 593, titled; An Effectiveness Study of the Infantry Rifle. The Hall Study concluded that soldiers armed with smaller caliber, high velocity rifles would be more effective then soldiers armed with the M1, in several ways. First and most importantly they possessed a greater single shot kill probability.

Three months later in June of 1952 the Army's Operational Research Office published the Hitchman Report, titled Operational Requirements for an Infantry Hand Weapon The Hitchman report concluded that it was possible to "create militarily acceptable damage at common battle ranges with missiles of smaller caliber then the present standard .30 caliber without loss in wounding effects and with substantial logistical and over all military gains.

Development of what became the 5.56x45 round we use now started from these reports. Nowhere does anyone mention we'll design a cartridge to wound so it will stress the enemy's logistical system.
 
Heinlein summed it up quite nicely. Anytime someone asks "why do they" or "why don't they," the answer is money.
 
Interesting thread. IMO, we will not see a caliber change until we see the adoption of a weapons system providing a strategically significant leap over the AR/Stoner system. As of now, there are better weapons out there but they aren't superior enough to make a critical difference in a conflict.
 
Kinetic energy is important and the 6.8 outdoes the .223 pretty easily on that.

Taylor KO factor is only one equation and if a person chooses to ignore it I have no complaints but you cannot ignore momentum.

bullet momentum/ impetus is much more significant when you want to drop the bad guy more reliably.

A heavier object has more inertia than a smaller one. When you have it traveling at a velocity that isn't too far below its competition it will be noticed. Against people in body armor, momentum becomes very important. You may not defeat the body armor but you can still shock the bad guy.

.223 hits on ceramic plate may not even be noticed in the heat of combat. Kinetic energy is not measured in gravitational pounds. It cannot move a 1300 lb object one foot in a frictionless enviroment. Momentum can move an object. A .223 has on average about 25 to 29 lb ft sec of momentum. If it transfers that much momentum to a 25 lb object in an enviroment free from friction it will move that object 1 foot per second. Or it can launch a 1 pound object 25 feet per second. It could in a controlled enviroment move a 150 lb object 1/6 of a foot per second.

The 6.8 has momentum into the 40+ range. So it generally has close to twice the momentum.

Spec ops give the 6.8 the nod. I would trust their opinion over a soldier who has also seen combat but only observed the capablities of the .223.

Than bullet performance is considered. We can theorize that if the bullet design is the same (fmj) than we can use Taylors knockout formula to compare performance. The formula adds the last bit of information , bullet diameter.

Bullet diameter will help determine how much of the momentum will remain physical momentum. A bigger bullet will not penetrate or generate heat as well as a smaller diameter bullet. This is why the 45 acp scores so high is because it doesn't particularly penetrate well but it shocks its target a lot more. KO factor helps determine how strong a shock a cartridge will deliver not particularly what the permanent damage it will do.

This equates into what cartridge will deliver the most immediate stops. In this comparison, the 6.8.
 
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The point of shooting a deer with a big bullet is so that it does not run and you can't find it later.

The point of shooting a human with a .223 is to inflict a terminal wound on him - one which will put him down instantly, or in a matter of seconds or minutes, or cause his comrades to expend energy and time trying to get the incapacitated or mortally wounded person out of harm's way. It takes a man out of the fight. Since we don't plan on eating them later, it does not really matter if they retreat or not so long as they've been effectively taken out of the fight (which they very much are in most circumstances). With that in mind, any tidbits about deer hunting do not really apply to the argument at hand.

But just to put it out there: a .223 will put a deer down almost instantly very well if the shooter does his/her part.

Another thing to keep in mind is that you are comparing what a .308 does when looking at what the .223 does. The .308 hits more than twice as hard as the .223 and almost twice as hard as 6.8 (some common loads average at about 3,300 ft-lbs). So really, why argue for the 6.8 when it still doesn't come close to the performance of your one-hit fringe hit stopper that is the .308? We're arguing intermediate calibers here, and the longer-range and flat-shooting 5.56 is an intermediate caliber that is more than adequate. So why switch? Because we want to make sure the marines have a caliber good for killing their enemies and then being able to go hunt deer to celebrate their victory? The .223 would be good for that already anyway.
 
Ive never met a "Spec Ops" guy who said the 5.56 was a bad round. Hell three of my old squad mates are Green Berets now. The ODA squad at my FOB in 05 all used 5.56 M4s and didnt complain. They could use anything they want, hell their sniper had a 300 win mag, but they still used the 5.56.

I like how people on these boards with no combat experience like to tell veterans with combat experience whats what.

Ive personally seen plenty of bad guys killed with the 5.56. Ive never seen anyone hit with a good COM shot with the 5.56 live. I have seen it once with the 7.62. Why?? Because that guy was one tough sob.
 
Christ you aren't kidding.
And what the heck is 'Spec Ops?' Are you talking Naval Special Warfare, Army Special Forces, MARSOC, JSOC, or what? No one in the community uses that term.
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I am glad I am not part of the community. It saves a lot of typing to just categorize them all into a simple word.

They are all under SOCOM anyways arent they? Special operations command = spec ops.

spec ops

http://www.fas.org/irp/agency/dod/socom/index.html

My last two cents

If you can convince me that a .223 can take down a man more reliably than a 6.8mm or a .308 than my understanding of physics is exactly the reverse of everything I have ever been taught.
 
If you can convince me that a .223 can take down a man more reliably than a 6.8mm or a .308 than my understanding of physics is exactly the reverse of everything I have ever been taught.
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That's your problem, there is a lot more then physics involved. Terminal performance of the round, physiology, and plain old human spirit all figure into this equation. You can just forget any kind of mathematical formulas. There are too many variables to figure into it.

5.56x45 has been killing our enemies since the early 60s. Are there better rounds out there? Probably. Are any of them going to give us enough of an improvement to justify the change? No.

I personally like the 6.8 SPC. I've talked to Dr. Gary Roberts who did the ballistics testing on the round and assisted the members of 5th Special Forces who developed it on their own at length about it. I think it's an improvement, but the 6 million dollar question is, is it enough of an improvement to justify the expense to change? Considering that there are no systematic lethality problems with M193, M855 or MK262, I don't think it is a big enough improvement over what we are using.
 
Nobody is saying the 5.56 is better at taking down an enemy than a 6.8 or a .308. But saying its not good at it is just plain false.

There will always be a bigger and better. But in combat you have to balance recoil, weight, accuracy, range and effectiveness with your load. You can easily upgrade the last one but it will usually negatively effect the other aspects. The 5.56 works very well as a combat round because it has all the basics balanced pretty well.
 
In my opinion the amunition the troops use has to do two things good.
To reliably kill humans and to have some barrier penetration capability so it can get to the human hiding behind it.
With a small caliber, because of the low weight, you can't do both this things great. You can do one of them great and the other one bad, or try to do them both so-so.
First the 5.56x45 was doing the killing good, but had really poor penetration.

After some modifications, the penetration was improved but because of that bullets are now more stable and don't fragment as reliable. Without early enough tumble and fragmentation you are just left with a small .22 hole in the bad guy. Unless something vital was hit, that small hole won't drop the bad guy and he can still fight.

A larger caliber, heavier modern bullet, has a lot more chances to do both much better. More mass means higher kinetic energy and momentum to help with both
1)better barrier penetration and
2)more and bigger fragments to damage tissue and kill the bad guy faster.

Sure most of us here in the west hemisphere would stop fighting right there and then if we got hit by a non fragmenting 223, but we find our troops fighting jihadists this days.
This guys are there to try to bypass the slow and painful "going to heaven system".

Think about it. This guys live in some bad, poor places, all they have is the Islam.
They got tired of the hard life they have to put up with every day so "martyrdom" looks like a quick way to change the crappy hard life (most of this poor guys have to put up with), for heaven.

This guys are not there sent by someone by force, they are there to kill our troops and die as martyrs in the process. Going home wounded is not what they are looking for.
So many of them don't stop fighting when the heaven is so close.
That's why now I think a heavier bullet would be a lot better against this type of enemy because modern bigger bullets, like 6.8x43mm, DO kill faster.

Just like the appearance of the kamikaze planes made the navy to arm a lot of their fighters with 20mm cannons instead of .50's. The fifties did kill planes, specially unprotected/unarmored Japanese planes, but the quad 20mm package killed them a lot faster.
We all saw plenty of WW2 footage with burning kamikaze planes crashing onto US ships. Is a bout the same with the enemy our troops face this days.

I also think that against the enemy we face today the care for the wounded enemy combatants is falling on our friendly forces more then we would like to admit.
There are plenty wounded enemy combatants treated out of our money.:(
 
lets just make the 5.56 a hare bigger,let's say we open it up to 6mm and add a cm or two to the width ,this would give you 65 to 110 gr and more powder;).
 
Jaws.... the problem is that a marginally bigger round still has to hit a vital area to drop a bad guy DRT reliably. In all reality if a .308 drops a bad guy DRT a 5.56 in the same spot probably would have also. A larger bullet isnt going to make that huge of a difference in non COM hits unless you really stepped it up to something like a .338 Lapua or a .50 BMG.

Also if the 5.56 doesnt yaw or fragment it still does more damage than just a .22 caliber hole. You got the whole "hydrostatic shock", or whatever you want to call it, aspect of rifle ballistics.

Also, in my experience, a 5.56 that hits bone leaves really gruesome and nasty wounds. Ive seen shots that exited the shoulder blade leave exit wounds almost the size of baseballs.

I will say though that I do believe the current bullet we have loaded could be better. I believe the somewhat complex nature of its construction can affect how the bullet performs from lot to lot. I saw a test somewhere where they shot them into ballistics gelatin. Some rounds yawed early and some yawed at close to 11-12 inches. I believe switching to a heavier plain jane FMJ bullet similar to the M262 would be better.

If I had to go back into combat again and could choose any weapon, I would still choose my 20" M16 DMR I had in 05.
 
Hydrostatic shock is unpredictable in its effects. It depends on where it hits and whether it hits fatty tissue, muscle tissue or bone.

Heavier bigger diameter bullets (that still deliver Hydrostatic shock) are much more predictable in what they will do.


My uncle in WW2 fought against the Japanese and survived several bonzai attacks as a BAR gunner. He wouldn't have trusted his life to a .223 against an enemy who is prepared to die.


A lot of the problem is not if the US can switch but trying to get NATO to switch. The US has proven time and time again to switch a cartridge if it is advantageous but that was before NATO.

You are no longer dealing with engaging targets some distance away like in the Gulf War (That was when I served). You have an enemy now who is so close that using your sights may not always be the most practical thing to do due to reaction speed.

A USAS-12 firing slugs would be the best weapon for this kind of fighting.

A .308 or a 6.8 would be the next best thing.

The MK262 is a good idea and if the army doesn't switch calibers I hope they at least can switch bullet weights.

In Vietnam the claims of US troops kill rates against the Vietnamese could never be substantiated scientifically.

Absence of evidence was the problem. Despite the claims of US troops far fewer bodies were found on the battlefield despite the sure claims of soldiers that they shot many Vietnamese.

The US suspected a Vietnamese conspiracy that they dragged away their dead before US troops could overrun the area for propaganda reasons.

This seems highly unlikely for if it is the case very few of these body draggers were ever caught and considering their stealth they should have been able to overrun every base we had in Vietnam with their magical Ninja abilities.

More than likely the "dead" carried themselves off the battlefield.

In close quarter fighting training can only carry you so far in a firefight. A bullet does not become afraid. it will fly straight and true in whatever direction it is fired. The biggest reason why US troops do not suffer more deaths is due to high quality body armor that can stop high powered rifle bullets. Also an abundant supply of grenades.
 
Ned, first of all, Thank You for your service.What branch were you with? Ned,the NVA did drag their wounded and dead off. This was heard at night. Ned, I know you do not like the 5.56 round. My experience was with the M 193 round. It killed. I never had a man get up. Ned, you seem to have it in for Nam vets. We put up with a lot when we came home and I guess a few more comments will not affect us. I hope your anger can be laid to rest. It was my honor and duty to fight for The USA and to help provide a future for those that came after us. I will leave a verse that has given me great comfort in the years after Nam and still to this day. Jeremiah 33:3.
Peace to you. Byron
 
The 5.56 works, anyone who says otherwise doesnt know their Butt from a goundhoghog hole.
Now with that said, there is no advantage to switch to the 6.8 for the military. In fact the 6.8 was offered to the military then offered to the professional security world because the military is not interested. So no US unit uses it in the M-4 or M-16 period. Even the top SF units use the 5.56 in the H&K 416, not 6.8.
Im sure this question will be asked a million more times before most get it through their heads.
The US has killed and permanently stopped more enemy combatants with the 5.56 than anyone else, why should we switch? Why did the Israelis switch from the 7.62 of their own rifle design to our M-16 in 5.56 many years ago, it worked better. why did every country in the free world switch aside from a few, it works better.
Until something that shows much more capability and reliability comes along it will continue to work better.
If you ever went to combat with the 5.56 you would never ask why.
 
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