.223 or 5.56 what's the difference?

Discussion in 'Ammunition & Reloading' started by WDbeej, Jun 28, 2011.

  1. WDbeej

    WDbeej New Member

    Ok, I'm new to shooting, but I love to learn.

    What is the difference between .223 & 5.56?

    If .223 and .22 are the diameters in inches, why is there such a big difference in .003 of an inch?

  2. Jpyle

    Jpyle New Member

    It's not just the diameter that matters. The shape of the .223 versus the .22lr (pictured) combined with the huge differences in powder charge of the rounds equates to a LOT more muzzle energy for the .223. As far as .223 versus 5.56, same round essentially but the 5.56 case is thicker and built to handle the higher pressure loads used by the military. A 5.56 chambered rifle can be used with .223 ammo but you should never use the 5.56 NATO in a .223 chambered rifle. The shorter throat, or Leade, of the .223 can cause dangerously high pressure in the chamber leading to a catastrophic failure or at a minimum deformed casings or cycling issues.

  3. c3shooter

    c3shooter Administrator Staff Member

    You can shoot .223 in a 5.56 chamber. You cannot always SAFELY shoot 5.56 in a .223 chamber. The chambers have slight differences. There is another chambering, .223 Wylde IIRC, that is AC/DC, goes either way.

    BTW, .308 Winchester and 7.62 NATO are the reverse. You can shoot 7.62 in a .308 rifle, but not all 7.62s can safely shoot .308.

    Somewhere, there is someone sitting there about to start typing "BS- I do that all the time." Yeah, and some people use a hairdryer while sitting in the bathtub. Just because it ain't killed you yet does not mean it is a smart thing to do.
  4. cpttango30

    cpttango30 New Member

    .223 Rem runs at a lower pressure than the 5.56mm. You can shoot 223 in a 556 chamber but you can't shoot a 556 in a 223 chamber. 556 are loaded with longer bullets and the chamber has more throat to it. Less throat allows the bullet to jam into the lands and grooves in the barrel causing pressure spikes.

    They are also not .223" in diameter. The bullet is .224" in diameter the barrel the lands are .223" and the grooves are .224" or there abouts.

    The case its self has the exact same dimensions for the 223 as the 556. The only real difference is that 556 military brass is thicker. If loading for 223 with milspec brass you MUST drop loads by 10% but not below book minimum.
  5. WDbeej

    WDbeej New Member

    Wow, thank you for the information.
    Jpyle, shooter, tango, thank you.

    So, would it be safe to ask that if I hypothetically did my own AR build, that I would have a more versitile rifle if I chambered it for 5.56? Or, is that not how it works?
  6. Jpyle

    Jpyle New Member

    Nope, that's exactly how it works. If you are building a general purpose rifle, a 5.56 chambered barrel or a Wylde barrel would be sufficient. Most upper assemblies sold today are either 5.56/.223 or Wylde.
  7. formerCav

    formerCav Well-Known Member

    another thing to consider if you are just now buying a AR-15 type rifle is barrel twist.
    I bought my first NRA service rifle used (dpms ar-15) and it cost me MORE then if I would have found out twist info FIRST!
    my used rifle had a 1 in 9 twist barrel. I could shoot 55, 68/69 and 75 grain bullets. But if I tried to shoot a 77 grain sierra match king (forget about the 80's) it would NOT group. Matter of fact, on SOME of the 75 grain hornady's it would NOT group. So I bought another upper with a 1 in 8 twist barrel and that allowed me to shoot the 77 and 80 grain bullets for NRA highpower. (55's won't group good now which does not matter to me as the ballistics on a 55 grain bullet are not really suitable for the NRA highpower games).
    If you get one with a 1 in 12 twist, it will just about be ONLY suitable for 55 grainers and less!
  8. alsaqr

    alsaqr Well-Known Member Supporter

    In 1968 i had a nice .222 Sako re-chambered for .223. That gun has fired at least 50,000 rounds of US military 5.56mm ammo through at least four different .223 barrels. i also own numerous other guns in caliber .223. They are also fed a steady diet of 5.56mm milsurp ammo. There are at least 12 different .223 and 5.56mm chambers. A gunsmith friend tells me that no gun maker presently uses a SAAMI chamber. It is true that 5.56mm ammo will not chamber in a tight .223 match chamber: Neither will .223 commercial ammo.

    It is a SAAMI myth that US made milsurp cartridge cases are thicker then .223 commercial cases. i've weighed the cases for my target reloads for over 40 years. Some Brit military ammo has very thick cases. The thickest cases of all are those made by Lapua.

    Got to cartridge case weights:

    AR15BARRELS.COM - Technical Documents

    It is also a SAAMI myth that 5.56 mm US military ammo is loaded to greater pressure than .223 ammo. Go to page 10-3 and find out that the pressure of the 5.56mm M193 military ball round is 52,000 psi.


    Let's see: The cartridge cases have the exact same dimensions and the military ammo pressure is lower than SAAMI specs for .223 ammo but you can't use 5.56mm ammo in a .223 chamber.

    For many years SAAMI said nothing about using 5.56mm military ammo in .223 chambers. Then when all that milsurp ammo became available SAAMI made up their myths because it was cutting the bottom line of US ammo makers.
    Last edited: Jul 11, 2011
  9. Dillinger

    Dillinger New Member

    Let's see.... How detailed do you want go??

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