Okay I know this is an idiot question but.

[Gunner]

Will a .223 rifle also shoot 5.56? I just want to make sure

Thanks
Landon

[patrick0685]

from what i understand 5.56 cases are slightly different from .223, but also understand 5.56 barrels can shoot both, .223 barrels you should stick with just .223, iv also heard that you can get a more accurate .223 barrel/gun than a 5.56. open to all corrections

[scratchy]

They are not the same. Weapons chambered for .223 Rem should not be used to fire 5.56 ammunition. Generally, rifles chambered for 5.56 can fire either. Do the proper homework before firing 5.56 in a .223 chambered rifle.

http://en.wikipedia.org/wiki/.223_Re...s_5.56_mm_NATO

[spencerhenry]

i read it on the internet so it must be true.

.223 and 5.56 are exactly the same in dimension according to several of my loading manuals. military brass is supposed to be thicker walled. my most accurate AR is labeled 5.56 nato, but i load it with .223

[theGinsue]

Scratchy is correct.

There are pressure considerations that can get you into trouble.

In a gun chambered for 5.56mm, you can shoot both 5.56 & .223
In a gun chambered for .223, you can ONLY shoot .223.

Everyone knows someone who says that they shoot 5.56 and .223 interchangably in any .223 rifle. While you might just get away with doing this for a while, it would be nothing short of playing roulette - it might be the first round or the 50th that blows the gun apart and takes your hands and face with it.

[68Charger]

This is the best illustration of the difference in dimensions that I have seen:

http://www.ar15barrels.com/data/223vs556.pdf

[theGinsue]

I actually had this information in a document on my work computer, so, here you are:

Source: http://en.wikipedia.org/wiki/.223_Remington

The .223 Remington is a sporting cartridge with the same external dimensions as the 5.56x45mm NATO military cartridge. It is loaded with a 0.224-inch (5.7 mm) diameter, jacketed bullet, with weights ranging from 40 up to 90 grains (5.8 g), though the most common loadings by far are 55 grains (3.6 g).

The primary difference between .223 Remington and 5.56x45mm is that the .223 is loaded to lower pressures and velocities compared to 5.56 mm. Thus, .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.



223 Remington versus 5.56 mm NATO

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)[2], and the NATO specification allows a higher chamber pressure. Test barrels made for 5.56 mm 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 5.56 mm NATO, is around 78,000 psi tested in .223 Rem test barrels (SAAMI .223 Rem Proof MAP is 78,500 psi so every 5.56 mm 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[3] or the Armalite chamber, which are designed to handle both 5.56 mm and .223 equally well.

These 5.56x45mm NATO cartridges are identical in appearance to .223 Remington. They are, however, not completely interchangeable.

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 lead. [4] 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.[5] 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[6], 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.

[cleaner72]

Scratchy is correct.

There are pressure considerations that can get you into trouble.

In a gun chambered for 5.56mm, you can shoot both 5.56 & .223
In a gun chambered for .223, you can ONLY shoot .223.

Everyone knows someone who says that they shoot 5.56 and .223 interchangably in any .223 rifle. While you might just get away with doing this for a while, it would be nothing short of playing roulette - it might be the first round or the 50th that blows the gun apart and takes your hands and face with it.

Ginsue is correct its all about the pressures..... 5.56 will take both .223 only in a .223

[SA Friday]

OK, here's a monkey wrench it everything for you all: Why? The 5.56 chamber actually has a little less metal around it in comparison to the 223 if the specs chart attached is correct. All barrels in an AR fit in the upper at the same diameter, right? The rounds can only be loaded to a certain length as the mag is the limiting factor for OAL in both chambers. So, the amount of pressure difference can't be all that much; 5,000 PSI maybe? So, which factory is loading 60,000 PSI 223 or 5.56 ammo? I don't know of any pushing the limits that hard with any bullet weight, not even nato. 223 and 5.56 will both chamber in each other's chambers with full bolt lock-up.

So... I don't get it. SAAMI sets standards, but that doesn't mean the standards are completely correct as they have to set the standards for the lowest common denominator. 45LC and 45-70 are both great indicators of this. You can load 45LC to surpass 44 Mag ballistics if shot out of a Ruger, but the same will kaboom another gun made to the black bowder specs. Has anyone actually seen (don't want to hear you read it in a blog this one time on AR-15 dot com...) an AR kaboom from this? No other reason it could have kaboomed? I have to ask as I've been shooting 15's and 16's since I was 11 and have yet to actually see one blow from using 5.56 in a 223 chamber in an AR, and bro, I shoot quite a bit. I could see how this might be an issue in a Mini 14 or bolt gun, but an AR? Na, I just don't see it happening.

I'm open on this one. I could be disuaded from my position, but you better have some good evidence/bonafides to change my opinion on this one.