556 N 223,, the same or not ?

[Sigmar]

I have always been told 223 is fine out of a 556 barrel but not the other way around, headspace I think is the reason. However today I'm in a local gunshop where the owner is a "gunsmith", he says baloney. You can shoot a 556 out of a 223. So when I got home I pulled out my calipers and measured winchester 223, hornady 223 and independence 556. All the same weight cept the 556 is a noticeable hair longer. So wth is the correct answer ?

[Chuck 100 yd]

The 5.56 has a slightly longer neck than the .223 and can pinch the case mouth in some .223 chambers causing high pressures. The mil spec for 5.56 is also about 6,000 psi higher than the SAMMI spec .223 round. That is why it is said to be OK to shoot .223 in the 5.56 but not the other way around.
So bottom line, they are NOT the same.

[AJMD429]

What Chuck 100 yd said.

I would bet money (but not my fingers or eyes) that about any high-quality "223 Rem" gun would safely fire 55 grain "5.56 NATO" rounds, though. Main point to me is that if I got a good deal on 1,000 rounds of "5.56" ammo then I'd make sure to shoot it ONLY in a so-marked firearm. I keep things simple, and basically have never bought anything but "223" ammo other than an occasional box or two.

[Old Savage]

Well I would bet money there are differences because there are between 308 and 7.62x51.

[damienph]

Right or wrong; I shoot .223 and 5.56 interchangeably in three different ARs, a DPMS, Bushmaster and RRA and two bolts; a Savage 340 and a Savage 110. I have never had a problem.

[Mescalero]

It is a tale, told by an idiot, full of sound and fury; signifying nothing.

[damienph]

It is a tale, told by an idiot, full of sound and fury; signifying nothing.

Which is a tale? That they are interchangeable or not interchangeable? Which is idiotic? (who is the idiot )

[jkbrea]

The 5.56 has a slightly longer neck than the .223 and can pinch the case mouth in some .223 chambers causing high pressures. The mil spec for 5.56 is also about 6,000 psi higher than the SAMMI spec .223 round. That is why it is said to be OK to shoot .223 in the 5.56 but not the other way around.
So bottom line, they are NOT the same.

When I went to a patrol rifle instructor school, that is basically what I was taught. I order all our agencies ammo and we only order .223 because officers buy their own rifles and some are not rated for 5.56. Most barrels are stamped with either .223/5.56 or just .223. If it has 5.56, either round is safe.

I would venture to say the recipiant of either round could not tell the difference.

[Mescalero]

IF IT DOES NOT CHAMBER IN YOUR RIFLE, why are you trying to shoot it?

[sore shoulder]

Is Independence actual mil spec 5.56? And by that I mean does it have the higher velocities and the sealed case mouth and primer?

It's not the cartridge size that's the issue, it's the pressures.

Also the 5.56 chamber has a longer lead than a SAAMI .223 chamber.

If you wan to know if its safe, ask the manufacturer, they are the ones ultimately liable. IMO that gunsmith is irresponsible.

[Griff]

The mil spec for 5.56 is also about 6,000 psi higher than the SAMMI spec .223 round. That is why it is said to be OK to shoot .223 in the 5.56 but not the other way around.
So bottom line, they are NOT the same.

+1, the correct chamber for the NATO 5.56 has a longer leade, brass is the same length.

IMO that gunsmith is irresponsible.

+1, again, and for some facts and numbers: (to view my source article, click on the link in the "wrote" box... below).

The .223 Remington and 5.56×45 NATO cartridges are very similar, and externally appear the same. But there are some differences that lie beneath the surface.

The 5.56 case has thicker walls to handle higher pressures, meaning the interior volume of the case is smaller than that of a .223. This will alter the loading data used when reloading 5.56 brass to .223 specs.

Some 5.56 loads have a slightly longer overall length than commercial .223 loads.

The Chambers

The significant difference between the .223 Rem and 5.56 NATO lies in the rifles, rather than the cartridges themselves. Both the .223 and 5.56 rounds will chamber in rifles designed for either cartridge, but the critical component, leade, will be different in each rifle.

The leade is the area of the barrel in front of the chamber prior to where the rifling begins. This is where the loaded bullet is located when a cartridge is chambered. The leade is frequently called the “throat.”

On a .223 Remington spec rifle, the leade will be 0.085”. This is the standard described by the Sporting Arms and Ammunition Manufacturers’ Institute, Inc. (SAAMI). The leade in a 5.56 NATO spec rifle is 0.162”, or almost double the leade of the .223 rifle.

A shorter leade in a SAAMI spec rifle creates a situation where the bullet in a 5.56 NATO round, when chambered, can contact the rifling prior to being fired. By having contact with the rifling prematurely (at the moment of firing), chamber pressure can be dramatically increased, creating the danger of a ruptured case or other cartridge/gun failure.

The reverse situation, a .223 Rem round in a 5.56 NATO gun, isn’t dangerous. The leade is longer, so a slight loss in velocity and accuracy may be experienced, but there is not a danger of increased pressures and subsequent catastrophic failure.

How serious is the danger of firing 5.56 ammo in .223 guns? Dangerous enough that the SAAMI lists 5.56 military ammo as being not for use in .223 firearms in the technical data sheet titled “Unsafe Firearm-Ammunition Combinations.”

ATK, the parent company of ammunition manufacturers Federal Cartridge Company and Speer, published a bulletin entitled “The Difference Between 223 Rem and 5.56 Military Cartridges.” In this bulletin, ATK stated using 5.56 ammo in a .223 rifle could result in “…primer pocket gas leaks, blown cartridge case heads, and gun functioning issues.”

However, the danger may be lower than SAAMI or ATK suggest. In Technical Note #74 from ArmaLite, the company states “millions of rounds of NATO ammunition have been fired safely in Eagle Arms and ArmaLite’s® SAAMI chambers over the past 22 years,” and they have not had any catastrophic failures.

According to ArmaLite:

“Occasionally a non-standard round (of generally imported) ammunition will fit too tightly in the leade, and resistance to early bullet movement can cause elevated chamber pressures. These pressures are revealed by overly flattened primers or by powder stains around the primer that reveal leaking gasses.”
...

[Chuck 100 yd]

Great reply Griff ! Never hurts to know the truth.

[Sigmar]

Thanks guys, thats what I've always been taught, doesn't hurt to verify again

[mikld]

I have a Handi Rifle in .223. When I shot 5.56 (milspec and surplus) in it I got pierced primers, 2 or 3 out of 20, and only fair accuracy. I sent it to the factory, (about '90) and they replaced the barrel, saying nothing about .223 vs 5.56. Read a little/did some research. I tried 5.56 again, pierced primers. I handloaded some .223, light to medium loads w/50 gr. bullets, shoots fine, no pierced primers, good accuracy...

[williamranks]

There's an article on it in the 2013 Gun Digest, got mine at Walmart.
Basically a .223 chamber has to be reamed slightly to shoot 5.56 like Griff said.

[cas]

The CARTRIDGE is the same size, the max CUP and chamber specs are not.

I HAVE seen problems from people firing 5.56 in a .223 a number of times. Badly stuck cases and blown primers from the pressure spike.

http://www.thegunzone.com/556v223.html

[Tycer]

There's an article on it in the 2013 Gun Digest, got mine at Walmart.
Basically a .223 chamber has to be reamed slightly to shoot 5.56 like Griff said.

Sounds like an easy fix. Spin a finishing reamer in there if you want to shoot both in one marked only 223.

[piller]

Good info. I have one of DPMS's ugly black rifles. I just looked and it is marked Cal .223-5.56MM and it shoots whatever brand I buy for it. The accuracy is on par with the M16A2 that I shot for qualification in the Army. Apparently there is not much difference in accuracy with anything from 45 to 62 grains when I shoot them. Maybe a better shot than I could see the difference.

[damienph]

Beginning my post with the statement ”Right or wrong” may have sounded cavalier to some of you but that was not my intention. By “right or wrong”, I only meant that I didn’t know that it was considered wrong, or unsafe, to fire 5.56 ammunition in a .223 chamber.

A few years ago, I was fortunate to trade into a quantity of M193 55 gr FMJ ammunition. The ammunition was boxed MAL 9-82 M193 and a loose packed mix of LC 01 & LC 02 XM193. It all shot fairly well in my ARs so I tried it in my two Savage bolt rifles. The 5.56 chambered easily, the bolts on both rifles closed and opened without any difficulty or extra force. The ammunition wasn’t incredibly accurate in any of my rifles but shot well enough to plink with.

I never had any high pressure signs, such as excessively flattened or loose or pierced primers. As I said before, I fired the MAL and the LC in both rifles with no ill effects what so ever. Two friends of mine also tried the MAL in their rifles with no problems. One was a Stevens 200 and the other was an H&R Handi-rifle.

A side by side comparison of a Remington UMC 55gr FMJ and the Lake City 5.56 M193 looked identical to me.

After reading through the other posts in that thread, I started looking (on the internet) into the differences between the two cartridges. It seems to me that the problems of high chamber pressure in the .223 chamber are associated with the higher pressure M855 ammunition, not necessarily with the M193 which according to what I have since read is loaded to the same pressures as .223 and lower than the M855. Essentially every article that I read ended with the statement that “dangerous pressures MAY occur”.

My post WAS NOT a recommendation that anyone fire 5.56 ammunition in a rifle chambered in .223. I was merely stating MY experiences with 5.56 ammunition in MY two Savage bolt action rifles. In my rifles, I had no problems shooting the M193 5.56 ammunition that I had interchangeably with .223 Remington ammunition. Remember, the SAAMI warning states that dangerous pressures “MAY” occur.

I have been handloading since 1976 and have loaded tens of thousands of rounds for at least 40 different cartridges over the past 37 years without any mishaps what so ever. I have been a shooter since I received my first rifle, a Remington 514, for my seventh birthday in 1961. I honestly had never heard of the problems with interchanging .223 and 5.56 and if I had problems chambering the rounds or had experienced any high pressure signs, I would have stopped at the first indication.

To be called an “idiot” by a fellow forum member and the implication that my post was “a tale,… full of sound and fury; signifying nothing” was in my opinion, uncalled for and insulting, and tends to stifle any conversation, at least for me.

[Mescalero]

I did not mean to insult anyone.
If you feel that way I apologize.
It was a quote from Shakespere.
That is all.
Interchanging of the two cartridges has been going on since it''s inception.
Only the introduction of newer modern loadings has changed the parameters.

[Old Savage]

Because I have a BLR made by Miroku marked .243 Only that will pierce the primers on some factory ammo or would before the chamber was cleaned with polishing paste I am aware that in some instances tight chambers combined with small leade and tight barrel dimensions can cause problems or cartridge failure I can see the possibility of the issue. I also have a 308 that will get cases stuck using at least one kind military ammo. Of the many other rifles I have had loaded for or shot there has been no identifiable issue and had I not experienced these incidences I might have considered that they were theoretical. There were a few of one make of .243 some time ago that came apart with some throat erosion with a certain style of leade. This is a game of trying to stay on the safe side.

On the discussion I might say from an observers stand point (don't own a .223) The initial post asks a question. The next by the OP states a personal conclusion to there were two different takes to interpret. My wife tells me that people often do not take what I am explaining if it is technical the way I mean it. Mescalero is not as I recall one who tends to insult people but seem to me to address issues yet it could be taken as personally insulting, he did venture into a literary reply here. On the OPs side is the common disclaimer used by many writers " these loads have been safe in my guns" implied - as I load.

This has been an interesting discussion - points I had no idea were included in the issue - and since I intend to get a .223, relevant in a personal sense. Thanks for the post and the contributions.

And now I see that mescalero - that rascal, has snuck in and stolen the "sound and fury" from my Shakespeare recognition before I could make it, while i wqs posting - dagnabit!

[mikld]

The 5.56 has a slightly longer neck than the .223 and can pinch the case mouth in some .223 chambers causing high pressures. The mil spec for 5.56 is also about 6,000 psi higher than the SAMMI spec .223 round. That is why it is said to be OK to shoot .223 in the 5.56 but not the other way around.
So bottom line, they are NOT the same.

Chuck got it!...