is a 5.56 x 45mm the same as a 223 cal?

Answer 1

Essentially yes! The main difference as mentioned above is a slight difference in the cartridge "neck" and SAAMI load presures. Also correct is that you can shoot 5.56 & .223 out of a 5.56 chamber, but cannot shoot both out of a .223 chamber. MOST guns today chambered for .223/5.56 come with whats known as a .223 Wylde chamber. Not quite 5.56 and not quite .223, its designed to give the best of both worlds so that either caliber (yes technically they are different calibers) will be fired as safely and accuratly as possible. You didnt ask, but figured Id mention anyway, but also very important in selection of a gun chambered in .223/5.56 is the twist rate of the barrel. If you see yourself shooting heavy bullets (55 grains and above, military surplus or hunting weight bullets) you want a barrel with a twist rate between 1 twist every 7 inches (denoted as 1:7) and 1 twist every 9 inches (1:9) this helps better stabilize the heavier bullets for uniform "spin" during flight. 1:9 is the most popular barrel twist rate. If you are looking for a fast moving, 35 grain spitzer bullet (match varmint ammo), a twist rate of above 1:9 is required, sometimes as high as 1:12 or 1:14. Lots and lots of information available here: http://www.ammo-oracle.com/body.htm good luck and safe shooting!

Answer 2

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. 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 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.

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.[2] 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.[3] 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.[4]


[edit] Comparison of 5.56 mm versus 7.62 mm NATO

Answer 3

Bound's hubby here:

The 5.56 NATO (European designation = 5.56x45mm, American designation = .223 Remington) is completely interchangeable with its civilian equivalents. As noted earlier by one of the respondents, military brass is thicker than commercial brass, which contributes to higher chamber pressures, especially if the same powder charges are used. But this is not unique to the 5.56 NATO round, it is a shared characteristic of the 7.62 NATO round (European designation 7.62x54mm, American designation = .308 Winchester) and the .30M1 (European designation = 7.62x63mm, American designation= .30-'06 Sprinfield)

An earlier respondent stated the military chambers are larger, yes, purely to ensure reliable functioning of ammo subjected to combat conditions. The larger chamber allows dirty or slightly dinged ammo to still function in combat conditions. Rifles generally can possess one of three types of chambers: military, commercial, and match chambers. These chamber types can possess different names. Military chambers are slightly larger to facilitate functioning in combat with dirty, damaged, or out of spec ammunition. Commercial chambers meet SAAMI specifications ... what all sporting rifles are expected to meet. Match chambers are tight tolerance chambers designed to reduce manufacturing tolerances and increase a firearms inherent accuracy.

Here endeth the lesson!

Answer 4

no, the 5.56 has higher chamber pressures. You can shoot .223 thru a 5.56 rifle, but not a 5.56 thru a .223.

Answer 5

Yes, they are essentially the same cartridge and they will interchange with no problems. One is metric (5.56) and the other is standard (.223).

Answer 6

Right on Johnny!