.223 v 5.56 Nato. The difference being...?

P

Pond James Pond

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As the title suggests.

I'd always thought that these two cartridges were the same, just with different names. However, some bits of literature infer that there is a difference because a rifle "can fire both".

It can't be the case or bullet calibre, so what is it? Power/Pressure?
 
I do not know for sure but I think it has more to do with the chamber of the rifle then the bullet it self . There still has to be something else though . :confused:

Just copied this from another site .I found it on the internet so it must be true :D

There is some overlap in the rounds, Im not sure of excact numbers but basically the 5.56 maximum overall length is longer then the max overall length for .223. So if you have a rifle chambered on the short side of .223 specs some 5.56 ammo wont work or be way over pressured when fired in the shorter chamber. If you are buying an Autoloader for volume shooting you should get a 5.56 chamber so you wont have problems with military surplus ammo

There are some 223 Remington rifles in which you wouldn't want to shoot 5.56x45 cartridges, some in which you wouldn't think twice, and some that you'd want to check before trying.
CIP standards (Europe) require pressure testing be done with the transducer at the case neck, where SAAMI cartridges typically measure with a transducer at the case head. You really can't translate directly from one to the other, but it's possible, perhaps even likely, that NATO loads will be at a higher pressure than is permissible in 223 cartridges, though not by a huge margin.
Also, it's been a long time since the standard military loads included a 55 grain bullet, and leades in military barrels tend to be pretty generous, giving up a little potential accuracy with those bullets to allow room to chamber the longer, heavier bullets common in military loads. Some civilian 223 rifles may not have the freebore to allow those bullets to be chambered safely, and if you're jamming the meplat of the bullet solidly into the lands, you're going to raise pressures.
If you have a strong bolt action like the Remington 700 action, it'll take a good deal of overpressure, though it isn't smart to get too smug about it. Additionally, if you want to be obsessive, you can measure the leade in your rifle to make sure there's a little room for the bullet to jump before it hits the lands. There are several ways to measure, some rather tedious, and probably the simplest/safest using a little gizmo made by Stoney Point.
 
This should help.

http://www.gundigest.com/223-vs-5-56


A .223 chamber has a shorter leade, or free bore, than a 5.56 chamber. It's theoretically possible for a heavy (longer) bullet in a 5.56 round to be jammed in to the start of the rifling in a .223 chamber. This could theoretically cause a over pressure situation. The bullet needs to have a short free space for it's initial movement.

I use "theoretically" because I don't see any reports of this happening, and a lot of peeps use 5.56 in .223 chambers.

Commercial .223 brass can be thinner than 5.56 NATO brass. The NATO brass may have a smaller volume than .223 brass.
 
The difference between the 223 & 5.56 only came about after the internet. Before that they were interchangable.
 
A gunsmith friend tells me there are at least one dozen different 5.56mm/.223 chambers. Here are some: Click on reamer dimensions:

http://ar15barrels.com/tech.shtml


Commercial .223 brass can be thinner than 5.56 NATO brass. The NATO brass may have a smaller volume than .223 brass.
Click to expand...

Since 1968 i've been weighing the cases for my accuracy loads. Some British made 5.56mm military brass is very thick. US military 5.56mm brass is not heavier/thicker than .223 made commercial brass. The heaviest US made cases are Federal Gold Medal. The heaviest cases of all are those made by Lapua.

Click on brass weights:

http://ar15barrels.com/tech.shtml


This young man did some fine research:

http://www.luckygunner.com/labs/5-56-vs-223/

Since 1968 i have fired at least a half million rounds of US military M193 5.56mm ammunition in the .223 chambers of numerous guns with no ill effects. Some of my guns have been re-barreled five or more times. i would not attempt to fire a US military 5.56mm round in a .223 match chamber.

i'm not suggesting that you fire 5.56mm ammunition in the chamber of your .223 rifle.
 
supposedly it's mostly the pressure of the rounds with a very slight chamber difference but there are strong arguments that interchangeability is a myth and that it is not. I just either buy rifles chambered in 5.56 or 223 wylde and don't worry about it.
 
The big problem is shooting 5.56 in a .223 chamber and getting it hot. (Like at a carbine training class)

The tighter .223 chamber "can" cause the primers to "pop" out of the case of a 5.56 cartridge and fall into the trigger mechanism. If that gets into the wrong place it can deadline the rifle until you can get that primer out, which might entail taking the trigger group out of the rifle.

There are several examples of this in Pat Roger's and others AAR for classes. They would usually "fix" them with a 5.56 chamber reamer to open the chamber up some. Ned Christiansen makes a reamer for this.

I have never had or read about an issue with anything blowing up or other damage, but having a primer tie up a gun isn't something that you would want to happen in a defensive situation.

Just target shooting or plinking shouldn't really be a problem.
 
When something is 5.56 mm x 45 mm it meets specifications demanded by NATO. For example, the brass is a touch thicker, primers are harder, primers are crimped into the primer pocket (a pain for reloaders) and there is a laquer seal around the primer to prevent water from getting into the case. Also, depending on which version you obtain, it's either going to be 55 g or 62 g bullets.

Manufacturers of civilian (.223 Remington) ammunition don't have to meet these standards. They have others.

I believe that automatic weapons and semi automatic weapons are going to have slightly larger chambers than those that aren't. That extra bit of play makes them more reliable. I think that a 5.56 chamber is slightly larger than one that is .223. You should be able to fire .223 out of the 5.56 mm rifle, but could have a problem the other way around.
 
I was surprised when I loaded winchester brass in place of military brass. With military, I used 25.9 grains of 748, and with winchester it took 26.4 grains to get good results. Brass thickness made a significant difference.
 
coyota1

I have not started reloading yet . I don,t even have one peace of reloading equipment but I do save all my brass for when I do . How can you tell them apart ( military brass vs commercial brass ) once they have been fired and all sitting in a bucket together . I my start a new thread asking this question in more detail
 
I was surprised when I loaded winchester brass in place of military brass. With military, I used 25.9 grains of 748, and with winchester it took 26.4 grains to get good results. Brass thickness made a significant difference.
Click to expand...

What was the headstamp on that military 5.56mm brass?

i've weighed US made 5.56mm and .223 brass cartridge cases since 1968 for my accuracy loads. i've weighed thousands of cases and never found US military 5.56mm cases to be thicker/heavier than US commercial .223 cases.

See brass weights:

http://ar15barrels.com/tech.shtml
 
im sure your aware but always check the barrel for the caliber to be shooting .233 and .556 are not the same. just as 7.62x39 is not the same as .308 my ar-10 wont cycle 7.51 but works fine with .308
 
im sure your aware but always check the barrel for the caliber to be shooting .233 and .556 are not the same. just as 7.62x39 is not the same as .308 my ar-10 wont cycle 7.51 but works fine with .308
Click to expand...


HUH

We're not comparing 22s with 223 Remingtons, we are talking about Military vs. Comerical names for the same round.

Like the 30 cal M2 vs the 30-06.

You'll get a bigger difference using differant reloading dies.
 
How can you tell them apart ( military brass vs commercial brass ) once they have been fired and all sitting in a bucket together
Click to expand...

I don't know that there is a hard and fast set of rules.

I'd start by looking on the bottom of the case.

If you see a colored ring around the primer, it's probably military. Sometimes, the stamp will say .223 or 5.56. Sometimes you can tell by the manufacturer - that is two or three letters on the head stamp. LC is Lake City - that's probably military brass. I have some that are AD which was military made in the Middle East.

I'm sure there are folks who know more about this than I do. Your notion of starting a new thread on it is a good idea.
 
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