.223 Rmington v. 5.56 mm NATO


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RonDurango
05-01-2009, 01:50 AM
I have always believed that the .223 Remington and 5.56 mm NATO cartridges are exactly the same with the only difference being that one is a metric measurement and the other is non metric. Today, a friend of mine told me that this is not true and that there is a subtle difference in the head size or pressure or something such that .223's can be fired in a rifle designated .223 or 5.56, but 5.56 can only be fired in a rifle designated 5.56. Is there any truth to this?

Are these two calibers the same? Can both be fired interchangeably in a Colt or Rock River AR15 marked .223?

There are so many knowledgeable people on this board that I am sure several of you will have the answer. Thanks in advance for the info.

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Sir Knight
05-01-2009, 05:25 AM
My understanding is that externally the two are identical but internally the 5.56 has a thicker case which increases pressure because it decreases the internal space. Thus, what you have been told is true -- you can shoot a .223 out of a 5.56 but you shouldn't shoot a 5.56 out of something chambered for a .223

melensdad
05-01-2009, 07:08 AM
The 5.56 pressure is tested closer to the neck in accordance to military testing standards, the 223 pressure is tested according to SAAMI pressure testing procedures and tested in the middle of the case. The 5.56 runs at a much higher pressure than the 223. While the cases are identical in outward dimensions, the pressures developed in the 5.56 make it POTENTIALLY dangerous to fire in a rifle marked and rated for the 223 round. The chambers are typically much looser on a 5.56 gun than on a 223 gun. This also makes for some interesting pressure differences when the cartridges are swapped and fired in guns.

Think of it like you'd think of +P or +P+ rated ammo. You may get away with firing +P in a gun that is rated for only standard pressure, but you may not! And if you don't do you really want to be holding the gun when it fails?

The one caveat to using the 5.56 round in a 223 chambered/marked/rated gun would be with the Ruger Mini-14 rifle. At least at one time, and I do not know this to be true for all Mini-14 rifles, but I believe it is, the Mini-14 is rated for the 5.56 and that IS stated in the manual. I know my Mini-14 is rated for 5.56 but marked 223. Now it is possible some are not rated for both rounds.

Sir Knight
05-01-2009, 07:36 AM
I don't know what they are rated, but I can tell you that the recent batch of mini-14's do not say 5.56 anywhere on the gun nor did a quick glance of the manual indicate that they were 5.56 rated either. I did not read the manual in detail but scanned it looking for "5.56" and didn't see it.

You see, having recently acquired an AR-15, I developed an interest in something "similar". The mini-14 was priced a few hundred dollars less and "looked" less threatening so I looked into it for that reason but given the fact that .223 ammo is running around twice (or more) as much as 5.56, I decided against it.

If Ruger chambered it for the 5.56, that would be next on my list.

jamesa
05-01-2009, 08:20 AM
I bought a new mini 14 in 08,was told it will shoot 223 and 5.56 no problem,went to range shot both no problem.
Plus it hits the target now.
Jamesa

Sir Knight
05-01-2009, 08:40 AM
That's interesting to know.

You were "told" that it would shoot both. May I ask what they based this on? I'm curious before I invest in one.

mbsieg1
05-01-2009, 08:43 AM
My Ruger manual says it will shoot 5.56. I will try to find an online manual. This is a new gun bought this year so maybe it has changed. Mike

mbsieg1
05-01-2009, 08:47 AM
http://www.ruger.com/Firearms/PDF/InstructionManuals/55.pdf

Please look at page 11. This should help. Mike

MtJerry
05-01-2009, 10:00 AM
Can both be fired interchangeably in a Colt or Rock River AR15 marked .223?


Yes ...

BigSwede
05-01-2009, 10:36 AM
My AR (Olympic Arms) is marked with both .223 and 5.56 designations...

Stevejet
05-01-2009, 01:56 PM
I'm at work and also too lazy to look it up, but a good number of "articles" - as in printed material in gun magazines - has addressed this difference many, many times.

If the issue of differences is really important, perhaps a Google inquiry is in order.

jamesa
05-01-2009, 03:14 PM
Ruger tech told me.

Stevejet
05-01-2009, 07:28 PM
Found this on Google.

There always seems to be a lot of confusion over the difference between a .223 and a 5.56 chamber. Is it safe to shoot this? Is it safe to do that? More confusion is added when some manufacturers advertise rifles with .223/5.56 chambers. I found this 'excellent' explaination on Wikipedia (http://en.wikipedia.org/wiki/.223_Remington) and wanted to share it on this forum.

The .223 Remington is a sporting cartridge with the same external dimensions as the 5.56x45mm NATO military cartridge. It is loaded with a .224" diameter, jacketed bullet, with weights ranging from 40 up to 90 grains, though the most common loadings by far are 55 grains.

The primary difference between .223 Remington and 5.56 x 45 mm is that .223 is loaded to lower pressures and velocities compared to 5.56 mm. .223 Remington ammunition can be safely fired in a 5.56 mm chambered gun, but the reverse can be an unsafe combination. The additional pressure created by 5.56 mm ammo will frequently cause over-pressure problems such as difficult extraction, flowing brass, or popped primers, but in extreme cases, could damage or destroy the rifle. Chambers cut to .223 Remington specifications have a shorter leade (throat) area as well as slightly shorter headspace dimensions compared to 5.56 mm "military" chamber specs, which contributes to the pressure issues.

While the 5.56 mm and .223 cartridges are very similar, they are not identical. Military cases are made from thicker brass than commercial cases, which reduces the powder capacity (an important consideration for handloaders), and the NATO specification allows a higher chamber pressure. Test barrels made for 5.56mm NATO measure chamber pressure at the case mouth, as opposed to the SAAMI location. This difference accounts for upwards of 20,000+ psi difference in pressure measurements. That means that advertised pressure of 58,000 psi for 5.56mm NATO, is around 78,000 psi tested in .223 Rem test barrels (SAAMI .223 Rem Proof MAP is 78,500 psi so every 5.56mm round fired is a proof load, very dangerous). The 5.56 mm chambering, known as a NATO or mil-spec chambers, have a longer leade, which is the distance between the mouth of the cartridge and the point at which the rifling engages the bullet. The .223 chambering, known as the "SAAMI chamber", is allowed to have a shorter leade, and is only required to be proof tested to the lower SAAMI chamber pressure. To address these issues, various proprietary chambers exist, such as the Wylde chamber[2] or the Armalite chamber, which are designed to handle both 5.56 mm and .223 equally well.

Using commercial .223 cartridges in a 5.56-chambered rifle should work reliably, but generally will not be as accurate as when fired from a .223-chambered gun due to the excessive leade. [3] Using 5.56 mil-spec cartridges (such as the M855) in a .223-chambered rifle can lead to excessive wear and stress on the rifle and even be unsafe, and the SAAMI recommends against the practice.[4] Some commercial rifles marked as ".223 Remington" are in fact suited for 5.56 mm, such as many commercial AR-15 variants and the Ruger Mini-14, but the manufacturer should always be consulted to verify that this is acceptable before attempting it, and signs of excessive pressure (such as flattening or gas staining of the primers) should be looked for in the initial testing with 5.56 mm ammunition.

This post has been edited by marsche: November 27th 2007 2:42 PM

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rotty
05-01-2009, 09:33 PM
Q. How can I tell if a round is SAAMI, US military, or 5.56 NATO Mil-Spec?

In the 1950's, the US military adopted the metric system of measurement and uses metric measurements to describe ammo. However, the US commercial ammo market typically used the English "caliber" measurements when describing ammo. "Caliber" is a shorthand way of saying "hundredths (or thousandths) of an inch." For example, a fifty caliber projectile is approximately fifty one-hundredths (.50) of an inch and a 357 caliber projectile is approximately three-hundred and fifty-seven thousandths (.357) of an inch. Dimensionally, 5.56 and .223 ammo are identical, though military 5.56 ammo is typically loaded to higher pressures and velocities than commercial ammo and may, in guns with extremely tight "match" .223 chambers, be unsafe to fire.

The chambers for .223 and 5.56 weapons are not the same either. Though the AR15 design provides an extremely strong action, high pressure signs on the brass and primers, extraction failures and cycling problems may be seen when firing hot 5.56 ammo in .223-chambered rifles. Military M16s and AR15s from Colt, Bushmaster, FN, DPMS, and some others, have the M16-spec chamber and should have no trouble firing hot 5.56 ammunition.

Military M16s have slightly more headspace and have a longer throat area, compared to the SAAMI .223 chamber spec, which was originally designed for bolt-action rifles. Commercial SAAMI-specification .223 chambers have a much shorter throat or leade and less freebore than the military chamber. Shooting 5.56 Mil-Spec ammo in a SAAMI-specification chamber can increase pressure dramatically, up to an additional 15,000 psi or more.

The military chamber is often referred to as a "5.56 NATO" chamber, as that is what is usually stamped on military barrels. Some commercial AR manufacturers use the tighter ".223" (i.e., SAAMI-spec and often labeled ".223" or ".223 Remington") chamber, which provides for increased accuracy but, in self-loading rifles, less cycling reliability, especially with hot-loaded military ammo. A few AR manufacturers use an in-between chamber spec, such as the Wylde chamber. Many mis-mark their barrels too, which further complicates things. You can generally tell what sort of chamber you are dealing with by the markings, if any, on the barrel, but always check with the manufacturer to be sure.

Typical Colt Mil-Spec-type markings: C MP 5.56 NATO 1/7

Typical Bushmaster markings: B MP 5.56 NATO 1/9 HBAR

DPMS marks their barrels ".223", though they actually have 5.56 chambers.

Olympic Arms marks their barrels with "556", with some additionally marked "SS" or "SUM." This marking is used on all barrels, even older barrels that used .223 chambers and current target models that also use .223 chambers. Non-target barrels made since 2001 should have 5.56 chambers.

Armalite typically doesn't mark their barrels. A2 and A4 models had .223 chambers until mid-2001, and have used 5.56 chambers since. The (t) models use .223 match chambers.

Rock River Arms uses the Wylde chamber specs on most rifles, and does not mark their barrels.

Most other AR manufacturers' barrels are unmarked, and chamber dimensions are unknown.

Opinion: In general it is a bad idea to attempt to fire 5.56 rounds (e.g., M193, M855) in .223 chambers, particularly with older rifles.

Fact: SAAMI specifically warns against the use of 5.56mm ammo in .223 chambers. The .223 SAAMI specification was originally made with bolt rifles in mind.

For more see the SAAMI website ammo warning.

Zen900
05-01-2009, 10:21 PM
http://www.midwayusa.com/Search/#340702____-_

.223 and 5.56 are the same size critter however, click on the pic of the ammo box in this link and read towards the bottom of the page about the SAAMI warning. There seems to be no way to end this debate one way or another. I just ordered this ammo for my mini-14 but I'm not sure if I should have. I did not read the SAAMI warning till just now. I'm sure you can load any ammo too hot though. Why should 5.56 or .223 be any different? I don't think this AE ammo is too hot for my mini. There is some 50gr .223 ammo on CDNN riht now that runs 200fps faster than this American Eagle ammo is chrono'd at. The SAAMI warning does not mean all 5.56 is loaded equally does it? Can you not also load .223 too hot?

Stevejet
05-02-2009, 01:08 AM
Yahoo Search provides this sample:

The question of whether these two cartridges are the same comes up often and I found a Winchester press release that is listed below. The cartridges look similar, but are not the same and it may be dangerous to fire 5.56mm ammo in a .223 Rem rifle. With all the 5.56mm surplus ammo on the market, it should not be fired in a .223. See the information quoted below from Winchester:



"Law Enforcement News and Press Releases Details


News and Press Releases

.223 Rem VS 5.56mm

Paul Nowak
5/4/2001
.223 Rem VS 5.56mm

There are a lot of questions about these two cartridges. Many people think they are identical - merely different designations for commercial and military. The truth is that, although somewhat similar, they are not the same and you should know the differences before buying either cartridge.


The cartridge casings for both calibers have basically the same length and exterior dimensions.
The 5.56 round, loaded to Military Specification, typically has higher velocity and chamber pressure than the .223 Rem.
The 5.56 cartridge case may have thicker walls, and a thicker head, for extra strength. This better contains the higher chamber pressure. However, a thicker case reduces powder capacity, which is of concern to the reloader.
The 5.56mm and .223 Rem chambers are nearly identical. The difference is in the "Leade". Leade is defined as the portion of the barrel directly in front of the chamber where the rifling has been conically removed to allow room for the seated bullet. It is also more commonly known as the throat. Leade in a .223 Rem chamber is usually .085". In a 5.56mm chamber the leade is typically .162", or almost twice as much as in the 223 Rem chamber.
You can fire .223 Rem cartridges in 5.56mm chambers with this longer leade, but you will generally have a slight loss in accuracy and velocity over firing the .223 round in the chamber with the shorter leade it was designed for.
Problems may occur when firing the higher-pressure 5.56mm cartridge in a .223 chamber with its much shorter leade. It is generally known that shortening the leade can dramatically increase chamber pressure. In some cases, this higher pressure could result in primer pocket gas leaks, blown cartridge case heads and gun functioning issues.
The 5.56mm military cartridge fired in a .223 Rem chamber is considered by SAAMI (Small Arm and Ammunition Manufacturers Institute) to be an unsafe ammunition combination.


Before buying either of these two types of ammunition, always check your gun to find what caliber it is chambered for, then buy the appropriate ammunition. Most 5.56mm rounds made have full metal jacket bullets. Performance bullets - soft points, hollow points, Ballistic Silvertips, etc. - are loaded in .223 Rem cartridges. Firing a .223 Rem cartridge in a 5.56mm-chambered gun is safe and merely gives you slightly reduced velocity and accuracy. However we do not recommend, nor does SAAMI recommend, firing a 5.56mm cartridge in a gun chambered for the .223 Rem as the shorter leade can cause pressure-related problems.

Winchester Law Enforcement Ammunition East Alton Illinois



Copyright 1997-2005 Winchester Ammunition, East Alton, IL 62024"

All the best...
Gil

Zen900
05-02-2009, 02:00 AM
The 5.56 cartridge case may have thicker walls, and a thicker head, for extra strength. This better contains the higher chamber pressure. However, a thicker case reduces powder capacity, which is of concern to the reloader

The 5.56 and .223 brass are the same. They vary no more than a remington 30-06 brass case from a Winchester 30-06 brass case. However, look at the 7.62x25 bullet. You can shoot nearly any 7.62x25 round out of your CZ52 pistol EXCEPT a variety mfg'd in Bulgaria that is loaded very hot for submachine guns. If you shoot this stuff in your CZ52 you may crack the slide.

The difference in 5.56 is not brass or bullet size but powder type and amount of powder. Apparently there may be some very hot 5.56 NATO loads out there but I've never seen any brands specifically ID'd as was the case with the Bulgarian 7.62 ammo. Even there it was not all Bulgarian ammo. It was just a specific brand in Bulgaria made for a specific gun. All the other 7.62x25 Bulgarian ammo was acceptable to the CZ52.

RonDurango
05-02-2009, 12:46 PM
Thanks for the input to my original inquiry. Having read your replies and checked with Rock River, my final conclusion is relatively straightforward. The .223 and 5.56mm are two are different cartridges with the 5.56 being a higher pressure round that should not be used in a weapon rated only for .223. However, some AR15s, specifically those made by Rock River, are rated capable of firing either round according to Rock River's website. So, the only way to be sure is check with your manufacturer.

Sir Knight
05-02-2009, 01:26 PM
Any rifle that can fire the 5.56 can also fire the .223 but not the other way around.

Sir Knight
05-02-2009, 01:27 PM
My Ruger manual says it will shoot 5.56. I will try to find an online manual. This is a new gun bought this year so maybe it has changed. Mike
http://www.ruger.com/Firearms/PDF/InstructionManuals/55.pdf

Please look at page 11. This should help. Mike
Ruger tech told me.That being the case, there may be a mini-14 in my future.

melensdad
05-02-2009, 04:21 PM
When speaking about calibers people use .223 and 5.56mm interchangeably. Just like some use 'clip' and 'magazine' and they are also not the same. Sometimes things are even more confusing with ARs. On some of their ARs Colt marks their lower receivers as .223 but then 5.56mm NATO on their barrels. Colts are chambered in 5.56mm NATO. This is okay since you can shoot .223 Remington in a 5.56mm NATO chambered barrel with no problems.

Max chamber pressure for 5.56mm NATO spec is 62,366 psi.
Max chamber pressure for .223 Remington SAAMI spec is 55,000 psi
5.56mm NATO, .223 Wylde and Noveske chambers can handle the high pressure levels of 5.56mm NATO ammo just fine. The 5.56 Noveske Match Mod 0 chamber is similar to the .223 Wylde chamber but is better suited for full auto use versus the .223 Wylde.

SAAMI spec .223 Remington chambers can be dangerous if 5.56mm NATO ammo is used in them, especially in older guns. Typically, in ARs it isn't dangerous, but .223 Remington chambers usually won't don't run well at all with 5.56mm NATO pressure ammo. The rifles will typically have failures to extract, blown primers, which will sometimes lock up the gun or make it not be able to fire. Sometimes that primer that's been blown out of the casing ends up under the trigger in the lower receiver and can keep the trigger from camming down when the shooter pulls the trigger to fire the rifle and the rifle won't fire.

Popeye
05-02-2009, 05:50 PM
Ruger is known for cutting "sloppy" chambers.

Sir Knight
05-02-2009, 07:15 PM
So does that mean a 5.56 can or can not be safely fired from a mini-14 chambered for the .223?

Popeye
05-02-2009, 07:17 PM
Yup. That's what it means.

Sir Knight
05-02-2009, 07:50 PM
"can or can not" ?

Popeye
05-02-2009, 08:20 PM
Can

Stevejet
05-02-2009, 09:29 PM
5.56MM ammo should NOT be fired in a .223 Remington chamber.

It (5.56MM) "can" be fired, BUT,,,,SHOULD NOT be fired from the .223 chanber!

paulb
05-02-2009, 09:44 PM
Says right in the Ruger manual you get with the mini 14 that you can use either!! Any other .223 you can't use both.

Popeye
05-02-2009, 10:06 PM
I say again, Ruger cuts sloppy chambers.

melensdad
05-03-2009, 08:14 AM
"can or can not" ?
Can
Says right in the Ruger manual you get with the mini 14 that you can use either!! Any other .223 you can't use both.
I say again, Ruger cuts sloppy chambers.
My Mini14 can shoot 5.56 or 223. Says so in the manual. The gun is marked for 223. The current manual on-line indicates that military ammo can be used in the Mini14 so my 10+ year old Mini14 and a modern version of the same gun can both use either round. Now Ruger may cut sloppy chambers, to that I do not know, but it strikes me that they may have considered the 5.56 surplus supply when they designed the Mini14 and simply cut the chamber for a 5.56 but designated the rifle as a 223 because Bill Ruger, when he was alive, was not a big fan of semi-autos, standard capacity magazine that would hold over 10 rounds, etc. So I suspect that slapping the 223 designation on the gun was a marketing designation to make Mr Ruger happy, while cutting a chamber to accept 5.56 surplus was a wise marketing choice to make consumers happy. JMO

Sir Knight
05-06-2009, 03:35 PM
Okay, I think I finally have all of this figured out. A couple of days ago we got a shipment in of several of them from Ruger and some were labeled ".223" while others were labeled ".223 (5.56)". The manuals that came with the .223 models make no mention of shooting the 5.56 out of it but the manuals that were included with the .223 (5.56) ones said that one could shoot the 5.56 out of it.

Based on that, I am concluding that Ruger makes two versions of their mini-14: (1) one that can handle the 5.56; and (2) another version that can't handle the 5.56 -- sort of similar to the SP101 -- some are .357mag while others are .38 only.

Eekamouse01
09-25-2009, 01:48 AM
I don't know what they are rated, but I can tell you that the recent batch of mini-14's do not say 5.56 anywhere on the gun nor did a quick glance of the manual indicate that they were 5.56 rated either. I did not read the manual in detail but scanned it looking for "5.56" and didn't see it.

You see, having recently acquired an AR-15, I developed an interest in something "similar". The mini-14 was priced a few hundred dollars less and "looked" less threatening so I looked into it for that reason but given the fact that .223 ammo is running around twice (or more) as much as 5.56, I decided against it.

If Ruger chambered it for the 5.56, that would be next on my list.
Just to reiterate on this, less there be any more confusion, both the out-of-production models, as well as the newer Mini-14 Ranch rifles fire both 5.56 and .223 rounds, as can be seen at the beginning of both owners manuals: "...The RUGER® MINI-14® RANCH RIFLES are offered in two calibers: the
.223 Remington (5.56mm) cartridge and the 6.8mm Remington SPC cartridge.
The Target Model uses .223 Remington cartridges only," (Sturm, Ruger & Co 2009) http://www.ruger-firearms.com/Firearms/PS-InstructionManuals-RI.html

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