Firing 5.56 in a .223 chambered rifle

Discussion in 'Auto & Semi-Auto Discussion' started by RufusTFirefly, Sep 29, 2011.

  1. RufusTFirefly

    RufusTFirefly New Member

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    I own an FNC semi-auto that is stamped "CAL. 223 REM SPORTER". Now the Belgian military FNC is chambered for 5.56 NATO. I got a gonga deal on 2,000 rds of 5.56 many years ago and have been firing those thru the FNC ever since. I was always under the impression that the two rounds were identical.

    Now I am reading that there is a *slight" difference in the chamber dimensions of .223 weapons and 5.56 weapons- and that higher than acceptable pressures can occur if 5.56 is fired in a weapon chambered for .223.

    So what do you all say? Is this overreactive hype? or should I be concerned?

    Thanks,

    Rufus
     
  2. 303tom

    303tom New Member

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    They are the same round, one military & one civilian !!!!!!!!!!
     

  3. neilage66

    neilage66 New Member

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    From wiki: .223 Remington - Wikipedia, the free encyclopedia

     
  4. canebrake

    canebrake New Member

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    They are NOT the same.

    [​IMG]

    Call FN and ask them.
     
  5. Yunus

    Yunus New Member

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    303tom, would you please edit your post. They are not the same round and someone searching via google with this same question might come across this thread and see your reply. They are similar but it's dangerous to shoot a 5.56 round in a .223 chambered firearm.
     
  6. 303tom

    303tom New Member

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    No i won`t !
     

    Attached Files:

  7. 303tom

    303tom New Member

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    Yes there is a difference between the military & civilian chamber, the military chamber is roomier to accommodate trash.
     
  8. 303tom

    303tom New Member

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    And before you get started on the thickness of the military case, yes they are that is to accommodate rough handling so you don`t have a bunch of dented up cases.
     
  9. Yunus

    Yunus New Member

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    Well at least your willing to contradict yourself in the same thread.

    Also as was posted by neilage66 and the OP there are pressure differences.
     
  10. JonM

    JonM Moderator

    Thats not true. I went through armourer school and it pretty much detailed the wiki article so much in fact i think they got the wiki info from the military training manuals.

    The thickness is not to promote rough handling the military doesnt reload. Military brass is recycled or left on the battlefield. Recycled brass the military sends back is melted to make new cases. The thickness is to prevent case failure due to the higher pressure loading of the 5.56 cartridge.

    Im not sure where you are getting your info. But the two are not the same at all. Ive personally seen two kabooms in the last decade from using nato surplus in civvy ar15 chambered for 223.

    Military 556 in 55 grn loading hits nearly 3200fps civvy 223 can barely reach 2900 fps in safe loadings.

    Military chambers have a long lead so they can use tracer ammo safely which has a greater bullet length than the same weight bullet in fmj format. Accuracy in military arms is not the main goal so a little extra bullet jump to hit the lands is not a big deal if the thing shoots 3 inches instead of 2.
     
  11. 303tom

    303tom New Member

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    Believe the (MYTHS) if you wish I know better, I been dealing with firearms & reloading for over 40 years, enough said !
     
  12. JonM

    JonM Moderator

    When some folks are given myths as facts then shown the real fact they cling to the myth cuz thats just the way its always been. It doesnt mean your stupid or wrong to just accept new info. It happens to me all the time. Taking it personally is the way to insanity.

    Ive had my assumptions and misinformation on things challenged here and ive gone to the effort to look for myself. Its not bad or makes you bad to change your mind especially where safe use of firearms is concerned.

    The two are close but they are very different. Much like 7.62x51 nato and 308 winchester. If you fire a 308 in a 7.62 chambering you stand a good chance of damaging your gun.

    Its the same principle as firing 38 in a 357.
     
  13. bkt

    bkt New Member

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    I tell you what...you prove to me that all the folks online who recommend against firing a 5.56 in a chamber rated for .223 are idiots who don't know their butts from page one and I'll listen to you. Until then, maybe you should throttle back on the hubris a little bit.
     
  14. alsaqr

    alsaqr New Member

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    Yep, the SAAMI myths are flying around today. US made 5.56mm cases are not thicker than US made .223 cases. The thickest US made cases are .223 Federal American Eagle and Gold Match. Some Brit 5.56mm military cases are thicker than any US made cases.

    The thickest and heaviest cases are made by Lapua. For 45 years i've weighed the cases for my accuracy loads. Before getting on a board and posting stuff as fact, you should weigh some too.

    Go to brass weights:

    AR15BARRELS.COM - Technical Documents
     
  15. 303tom

    303tom New Member

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    Throttle back, Roger That !
     
  16. 303tom

    303tom New Member

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    I did not write this.

    5.56 mm NATO versus .223 Remington

    The 5.56 mm NATO and .223 Remington cartridges and chamberings are similar but not identical. It is a myth that military 5.56mmx45 cases are made thicker and commercial .223 cases and military 5.56mm cases generally have the same case capacity.[17] 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.[18] 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)[19] 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.[20] 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.[21][22] 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.[23]

    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 litigation following the said injuries.
     
  17. jismail

    jismail New Member

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    I have heard about the .223 vs 5.56 but the .308 vs 7.62 is news to me. I have a M-14 and have shot tons of the bulk battle pack ammo from CTD, but also shoot commercial .308 when that is all I can get my hands on for the weekend. Are you saying it will damage my M-14?
     
  18. 303tom

    303tom New Member

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    I to shoot .308 in all my rifles chambered for the 7.62 NATO, my FR-7, my M-14, my 2A & 2A1, & you can`t shoot a .357 Mag. in a .38 SPL.
     
  19. FCross7

    FCross7 New Member

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    I did not write this. :)

    -Fred
     
  20. armsmaster270

    armsmaster270 New Member

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    At least the Ruger Mini 14's stamp that you can shoot both in their rifle.