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AR-15 ammo

Discussion in 'Rifle Discussion' started by hottip, Jun 1, 2012.

  1. hottip

    hottip Washington New Member

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    I have an Olympic Arms AR-15 and have been using 223 FMJ amo in it. Someone told me that I should use 5.56 ammo but I don't see the difference. Anyone have any recomendations and reasons one is better that the other, because I just don't get it.
     
  2. Nwcid

    Nwcid Yakima and N of Spokane Well-Known Member

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    There are very minor differences. For all practical intent they are both fine and safe in an AR.

    If you search the net for .223 vs 5.56 you will learn things you never knew you didnt want to know.........
     
    mjbskwim and (deleted member) like this.
  3. Key-Hay

    Key-Hay North Carolina Active Member

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    .223 in a 5.56 barrel is fine but don't shoot 5.56 in a barrel chambered for .223. If you barrel is wylde chamber your good for either. Rock Rivers and Bushmasters are Wylde (typically in higher end ARs).
     
  4. Key-Hay

    Key-Hay North Carolina Active Member

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    .223 in a 5.56 barrel is fine but don't shoot 5.56 in a barrel chambered for .223. If you barrel is wylde chamber your good for either. Rock Rivers and Bushmasters are Wylde (typically in higher end ARs).

    The 5.56 mm NATO and .223 Remington cartridges and chamberings are similar but not identical. Military 5.56×45mm cases are often made thicker and therefore have less case capacity.[18] However, the NATO specification allows a higher chamber pressure. NATO EPVAT test barrels made for 5.56 mm NATO measure chamber pressure at the case mouth, as opposed to the location used by the United States civil standards organization SAAMI. The piezoelectric sensors or transducers NATO and SAAMI use to conduct the actual pressure measurements also differ. This difference in measurement method accounts for upwards of 20,000 psi (140 MPa) difference in pressure measurements. This means the NATO EPVAT maximum service pressure of 430 MPa (62,000 psi) for 5.56 mm NATO, is reduced by SAAMI to 55,000 psi (380 MPa) for .223 Remington.[19] In contrast to SAAMI, the other main civil standards organization C.I.P. defines the maximum service and proof test pressures of the .223 Remington cartridge equal to the 5.56 mm NATO.
    The 5.56 mm NATO chambering, known as a NATO or mil-spec chamber, has 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 Remington 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)[20] or the ArmaLite chamber, which are designed to handle both 5.56 mm NATO and .223 Remington equally well. The dimensions and leade of the .223 Remington minimum C.I.P. chamber also differ from the 5.56 mm NATO chamber specification.
    Using commercial .223 Remington cartridges in a 5.56 mm NATO chambered rifle should work reliably, but generally will not be as accurate as when fired from a .223 Remington chambered gun due to the longer leade.[21] Using 5.56 mm NATO mil-spec cartridges (such as the M855) in a .223 Remington chambered rifle can lead to excessive wear and stress on the rifle and even be unsafe, and SAAMI recommends against the practice.[22][23] Some commercial rifles marked as ".223 Remington" are in fact suited for 5.56 mm NATO, such as many commercial AR-15 variants and the Ruger Mini-14 (marked ".223 cal"), 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 NATO ammunition.[24]
    It should also be noted that the upper receiver (to which the barrel with its chamber are attached) and the lower receiver are entirely separate parts in AR-15 style rifles. If the lower receiver has either .223 or 5.56 stamped on it, it does not guarantee the upper assembly is rated for the same caliber, because the upper and the lower receiver in the same rifle can, and frequently do, come from different manufacturers – particularly with rifles sold to civilians or second-hand rifles.
    In more practical terms, as of 2010 most AR-15 parts suppliers engineer their complete upper assemblies (not to be confused with stripped uppers where the barrel is not included) to support both calibers in order to protect their customers from injuries and to protect their businesses from resultant litigation.
     
  5. mortre

    mortre Yelm, WA Active Member

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    Should be good for either. FWIW my Olyarms AR-15 runs just fine with .223 Rem and my .223 Rem reloads. It has also ran fine with M855 and M193, however it choked on MK262 Mod 1 rounds. Doesn't really bother me as the barrel isn't twisted for that bullet anyway. If you stagger a mag with .223 and 5.56 rounds you can tell 5.56 is running at higher pressure levels. Looks like the Barnes 2010 manual lists loads for both. One example of same powder/bullet showed a starting load .5 grains higher in 5.56 than the max load for .223.
     
  6. PDXSparky

    PDXSparky Keizer / Hillsboro Well-Known Member

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    Did "someone" give you an explanation as to why? Otherwise, "someone" is just talking out their a**.
     
  7. madcratebuilder

    madcratebuilder Ardenwald, OR Well-Known Member

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    Some .223 can be under powered compared to nato 5.56 and cause short stroking and other problems. Your using .223 fine so no reason to change.
     
  8. mjbskwim

    mjbskwim Salmon,Idaho Well-Known Member

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    I did not read your other post as it was too long and drawn out,but I would guess most wylde chambers are just a 556 chamber with a new name (with in micro millimeters).
    I mean if it shoots both,safely ,as does the 5.56,what else would they change? And why?

    I believe the only time you have to check on this is for most bolt actions,as they are mostly chambered for 223,not 5.56
     
  9. DoubleTapDrew

    DoubleTapDrew Oregon Well-Known Member

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  10. DirectDrive

    DirectDrive Vancouver, WA Member

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    I wouldn't pay any attention to this "someone".

    As stated above, .223 is safe in 5.56 chambers but it's loaded to lower pressures.
    Be happy, you're cycling fine with your .223 ammo.
    Some AR's have to be "tuned" to cycle lower pressure .223 (and cheap imported) ammo.