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#740436 - 08/10/07 11:24 AM Dumb question on 5.56
Savage250 Offline
Die Hard Member

Registered: 11/30/04
Posts: 593
Loc: Oklahoma
I will be buying an Oly upper soon and their site says that their upper is 5.56 NATO. I thought that 5.56 was the same as .223 Rem. That's right isn't it??

Thanks,
_________________________
Anyone who is sworn-in to uphold the Constitution of the United States and then doesn't, should be convicted (not tried) of Treason and dealt with swiftly.
GAL 2:20
Savage250

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#740437 - 08/10/07 11:32 AM Re: Dumb question on 5.56 [Re: Savage250]
CatShooter Offline
PM senior

Registered: 01/24/02
Posts: 9094
Loc: The Socialist Republic of CT.
For the most part, they are the same, and won't effect you, but you will get five different opinions on this website (or any other), about what the subtle differences are.

Best advice is to call Oly and ask them. After all, they are the only people that really know.

.
_________________________
CatShooter
Spring has sprung, da' creek has riz, I wonder where dem kitties is.

Here kitty, kitty, kitty...

NRA Life member since 1965

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#740438 - 08/10/07 11:58 AM Re: Dumb question on 5.56 [Re: CatShooter]
slagmaker Offline
Die Hard Member

Registered: 11/17/05
Posts: 602
Loc: SE Indiana
5.56 and 223 are demenisionaly exeact duplicates of each other. The problem that can come up is if you shoot the NATO rounds out of a rifle that is chambered for only 223 you can damamge the internal workings "action" of your rifle due to the higher pressure/kick that the NATO rounds produce. I know that the NATO stuff used to use a hotter powder but as for the modern NATO I am not sure it may not be as hot as it used to be. I read this in an old reloading manual that my uncle had and for the life of me I cant remeber which one. If I can find it I will post the maker and edetion of the manual.

Best bet call Oly and find out
_________________________
"I would rather be ashes than dust! I would rather that my spark should burn out in a brilliant blaze than it should be stifled by dry rot. I would rather be a superb meteor, every atom of me in a magnificent glow, than a sleepy and permanent planet. The proper function of man is to live, not to exist. I shall not waste my days in trying to prolong them. I shall use my time." -Jack London *Dedicated to the crew of the Columbia - STS 107*

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#740439 - 08/10/07 01:46 PM Re: Dumb question on 5.56 [Re: Savage250]
Mavrick10_2000 Offline
Seasoned Member

Registered: 01/31/05
Posts: 372
Loc: Oklahoma
Like Slag said, higher pressures in 5.56. Check with Oly to be sure. Armalite, Bushmaster and a few others all support 5.56 pressures. I just can't remember if Oly is in the group.
_________________________
Bob Be Safe. Good Shooting! Former United States Marine NRA Life Member

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#740440 - 08/10/07 02:00 PM Re: Dumb question on 5.56 [Re: slagmaker]
CatShooter Offline
PM senior

Registered: 01/24/02
Posts: 9094
Loc: The Socialist Republic of CT.
Quote:

5.56 and 223 are demenisionaly exeact duplicates of each other. The problem that can come up is if you shoot the NATO rounds out of a rifle that is chambered for only 223 you can damamge the internal workings "action" of your rifle due to the higher pressure/kick that the NATO rounds produce. I know that the NATO stuff used to use a hotter powder but as for the modern NATO I am not sure it may not be as hot as it used to be. I read this in an old reloading manual that my uncle had and for the life of me I cant remeber which one. If I can find it I will post the maker and edetion of the manual.

Best bet call Oly and find out




Sorry... but NONE of the above is true.

You will hear tons of this stuff, and 99% of it is wives tales that get passed around with no fact behind it.

Both the civilian and military cartridges run in the same pressure range - ~55Kpsa, +/- 5Kpsa.

.
_________________________
CatShooter
Spring has sprung, da' creek has riz, I wonder where dem kitties is.

Here kitty, kitty, kitty...

NRA Life member since 1965

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#740441 - 08/10/07 02:26 PM Re: Dumb question on 5.56 [Re: Savage250]
bea175 Offline
Die Hard Member III

Registered: 11/30/04
Posts: 3295
Loc: Kingsport, TN, Graysontown, VA
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 (Rock River Arms)[1] or the Armalite chamber, which are designed to handle both 5.56 mm and .223 equally well.
_________________________
NRA Life Member Varmint Hunter ***. North American Hunting Club Buckmaster With Great Victories, Comes Great Sacrifice

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#740442 - 08/10/07 02:32 PM Re: Dumb question on 5.56 [Re: CatShooter]
Totch94 Offline
Die Hard Member II

Registered: 12/23/06
Posts: 1796
Loc: Central Mississippi
From the AR-15.com website:

Q. What is the difference between 5.56×45mm and .223 Remington ammo?

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.






Q. Which should I be looking for in an AR15, a 5.56 NATO or .223 Remington chamber?

This is really a matter of the role for which you plan to use your AR. .223 Remington chambers will give you slightly better accuracy, which is important for a match or varmint rifle. Any loss of feeding and cycling reliability and the restriction against shooting military ammo isn't as important as the accuracy gains for a rifle used in these roles, because for these rifles, accuracy is everything. People who just want to plink or who plan to shoot military ammo (such as most of the cheap surplus ammo available), and especially those who may use their AR as a weapon, should choose 5.56 chambers.
_________________________
"A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms shall not be infringed."
Second Amendment to the US Constitution December 15th 1791

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#740443 - 08/10/07 03:16 PM Re: Dumb question on 5.56 [Re: Totch94]
NM Leon Offline
Retired PM Staff

Registered: 02/05/05
Posts: 10335
Loc: AZ, NM, TX
SAAMI: UNSAFE ARMS AND AMMUNITION COMBINATIONS/TECHNICAL DATA SHEET


In Rifle Chambered For...
223 Remington

Do Not Use These Cartridges
5.56mm Military
222 Remington
30 Carbine
_________________________
"Government is not a solution to our problem, government is the problem." Ronald Reagan.

"Americans have the right and advantage of being armed-unlike the citizens of other countries whose governments are afraid to trust the people with arms." James Madison

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#740444 - 08/10/07 03:39 PM Re: Dumb question on 5.56 [Re: bea175]
CatShooter Offline
PM senior

Registered: 01/24/02
Posts: 9094
Loc: The Socialist Republic of CT.
Also... about 90% not true.

The military ammunition is NOT loaded to proof load standards.

The mean pressures of mil ammunition is in the range of 55Kpsia. The reason being is that since militrary ammunition is used in automatic weapons, the worst possibility is that a case throws a primer or sticks a case, and someone dies for it - no manufacturer would EVER send out service ammunition that ran 78Kpsia... and no type of firearm would be able to endure much of that ammo, without failing... certainly not a automatic weapon.

And the lock up of a M-16 is nowhere as strong as a M700.

... and where the sampling port on a pressure gun is located, has no bearing on the read pressure, except that it reads the pressure from that point on. In the case of the .223, since the peak pressure does not happen until the bullet is 5 to 8 inches down the barrel, it makes no difference whether the pressure port is on the shoulder or in front of the mouth, since both are exposed to the full pressure, and ALL pressure gages are calibrated for their specific uses.

In the hundreds of millions of mil-surp ammo sold and shot in civilian rifles, I have never heard of a single rifle failure of a well made rifle being damaged by military ammo being shot in it.

I knew this tread was on the way to the toilet when I read the question...

... and it'll get thicker and thicker.

.
_________________________
CatShooter
Spring has sprung, da' creek has riz, I wonder where dem kitties is.

Here kitty, kitty, kitty...

NRA Life member since 1965

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#740445 - 08/10/07 04:09 PM Re: Dumb question on 5.56 [Re: CatShooter]
Wingman26 Offline
Die Hard Member

Registered: 12/10/06
Posts: 802
Loc: Shawnee Oklahoma
Let's see....who do we believe? Since SAAMI is the organization that sets the standards for the industry, their credibility is quite a bit higher...
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#740446 - 08/10/07 04:11 PM Re: Dumb question on 5.56 [Re: CatShooter]
Savage250 Offline
Die Hard Member

Registered: 11/30/04
Posts: 593
Loc: Oklahoma
Thanks to all for the replies. I didn't mean to get anyone all worked up, I am just in the market for a "Varmint Style" AR and I was looking at Oly's K8CA and they say it's chambered in 5.56 only. If my accuracy is going to suffer while shooting .223Rem ammo in a 5.56 chamber, then I will try and go a different route. Where would you guys recommend getting a varmint (complete upper only) AR from??

Thanks for the help guys,
_________________________
Anyone who is sworn-in to uphold the Constitution of the United States and then doesn't, should be convicted (not tried) of Treason and dealt with swiftly.
GAL 2:20
Savage250

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#740447 - 08/10/07 04:19 PM Re: Dumb question on 5.56 [Re: Wingman26]
CatShooter Offline
PM senior

Registered: 01/24/02
Posts: 9094
Loc: The Socialist Republic of CT.
Quote:

Let's see....who do we believe? Since SAAMI is the organization that sets the standards for the industry, their credibility is quite a bit higher...




Yeah.. but what did they say, and why did they say it, and when did they say it.... and how does it apply to this.

It is easy to grab quotes from the internet, you can make a case for almost anything... but do they apply to the question, and are they relevant.

As to head space... the difference in head space between the .223 and 5.56 is 0.0003" (that's 3/10,000 of an inch)... there is not a gunsmith in the world that can hold chambers to 3/10,000"... and 90% can hold them to 20 times that amount.

And no cartridge maker can hold brass to 30 times that, so it's all about how many angles can sit on the head of a .223.

.
_________________________
CatShooter
Spring has sprung, da' creek has riz, I wonder where dem kitties is.

Here kitty, kitty, kitty...

NRA Life member since 1965

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#740448 - 08/10/07 04:43 PM Re: Dumb question on 5.56 [Re: CatShooter]
Restless Offline
New Member

Registered: 08/08/07
Posts: 22
Loc: OK
From the AR15.ocm site.

The current military specifications for the M16 5.56 series call for headspace of not less than 1.4646” and not more than 1.4706” on a new rifle. The commercial SAAMI gauges are marked in 1,000ths of an inch instead the 10,000ths of an inch that the dedicated M16 gauges are. When installing a new barrel, the commercial gauge measuring 1.465" can be used in place of the M16 "Go" gauge. Consider the 4/10,000ths of an inch difference an extra margin of safety. The commercial 1.470" gauge (the commercial "Field" gauge) can be used to confirm that the headspace is within spec for a new rifle. Unfortunately, there are no gauges available to measure between 1.470" and 1.4730", the latter being the measurement on the M16 "Field" gauge.

The M16 Field Service gauge measures a dimension of greater than 1.4730”. A rifle with a bolt that does not close on a Field Service gauge is considered safe to fire by the army, but not the Marines who use the military "No-Go" gauge for that measurement. Without using military Go or No-Go gauges, or commercial gauges marked with their measurements, you cannot know whether or not it is truly in spec. An interesting tidbit of information is that the Colt M16/AR15 Field gauge measures a dimension in excess of 1.4736”. It seems that the military has built in a bit more of a safety factor with their gauge.

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#740449 - 08/10/07 04:56 PM Re: Dumb question on 5.56 [Re: Restless]
Lungbuster Offline
Die Hard Member II

Registered: 12/07/04
Posts: 1170
Loc: Idaho
Savage250, If this is going to be a hunting rifle I wouldn't think your accuracy is going to "suffer" at all, You probably wouldn't even notice a difference. If you are buying it to shoot tight groups, that may be a different story....
_________________________
Then there came from hunting, the weather-eyed shooter.

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#740450 - 08/10/07 04:56 PM Re: Dumb question on 5.56 [Re: CatShooter]
NM Leon Offline
Retired PM Staff

Registered: 02/05/05
Posts: 10335
Loc: AZ, NM, TX
Quote:

Quote:

Quote:

I thought that 5.56 was the same as .223 Rem. That's right isn't it??



It is easy to grab quotes from the internet, you can make a case for almost anything... but do they apply to the question, and are they relevant.



SAAMI: UNSAFE ARMS AND AMMUNITION COMBINATIONS/TECHNICAL DATA SHEET
In Rifle Chambered For...
223 Remington

Do Not Use These Cartridges
5.56mm Military
222 Remington
30 Carbine




Seems pretty relevant to the original question to me. You're right though Cat, it IS easy to grab quotes from the internet. Even quotes from the folks who set the standards for sporting arms and ammo. Even quotes showing the latest info available from those folks, info that's on their website today.

Savage250, unless you distrust SAAMI for some reason, you can see that they are not treated the same. However, nowhere does it say you can't shoot .223 in a 5.56 chamber, and in fact, especially with an AR where the chambers are usually not tight because of the operating system, I've never heard of anybody having problems firing milsurp ammo from a .223 chamber, though that's not to say it couldn't happen, hence the warning.

Call the rifle manufacturer and get THEIR advice regarding THEIR rifle.
_________________________
"Government is not a solution to our problem, government is the problem." Ronald Reagan.

"Americans have the right and advantage of being armed-unlike the citizens of other countries whose governments are afraid to trust the people with arms." James Madison

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