Ok, stupid question, but I want to know

Discussion in 'AR-15 Discussion' started by 97powerstroke, Sep 9, 2007.

  1. 97powerstroke

    97powerstroke New Member

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    Just what is the difference between .223 and 5.56. I'm new to AR's and I thought they were the same rounds but that doesn't seem to be the case. Sorry for the dumb question but I would rather know then not know.
     
  2. bkt

    bkt New Member

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    Source: http://www.thegunzone.com/556v223.html

    Almost a quarter of a century ago, SAAMI recognized potential problems with shooters assuming that the 5.56mm cartridge was identical to the commercially available .223 Remington round. Here is their 31 January 1979 release, with some minor errors corrected:

    With the appearance of full metal jacket military 5.56 ammunition on the commercial Market, it has come to the attention of the Sporting Arms and Ammunition Manufacturers' Institute (SAAMI) that the use of military 5.56mm ammunition in sporting rifles chambered for Caliber .223 Remington cartridges can lead to higher-than-normal chamber pressures and possible hazards for the firearm, its user and bystanders.

    Tests have confirmed that chamber pressures in a sporting rifle may be significantly higher in the same gun when using military 5.56mm ammunition rather than commercially loaded Caliber .223 Remington cartridges, according to SAAMI.

    SAAMI points out that chambers for military rifles have a different throat configuration than chambers for sporting firearms which, together with the full metal jacket of the military projectile, may account for the higher pressures which result when military ammunition is fired in a sporting chamber.

    SAAMI recommends that a firearm be fired only with the cartridge for which it is specifically chambered by the manufacturer.​

    Additionally, SAAMI's Unsafe Arms and Ammunition Combinations Technical Data Sheet page states:

    The .223 Remington is rated for a maximum of 50,000 CUP while the 5.56mm is rated for 60,000 CUP. That extra 10,000 CUP is likely sufficient to cause a failure in a chamber that's only rated for the "sporting" .223 Remington.

    The .223 Remington and the 5.56mm NATO, when checked with a chamber ream from a reliable manufacturer of each, also have discernable differences in the areas of freebore diameter, freebore length (leade) and angle of the throat.
     

  3. AR Hammer

    AR Hammer New Member

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    Excellent!
    Glad to see someone else is trying to get the word out!
     
  4. 97powerstroke

    97powerstroke New Member

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    Thanks, now I know. Why is there no mention of this in any of my loading manuals? The only thing I could find in The three books that I have are about using the heavyer bullets in the higher twist rate barrels. 1 in 10 and higher. Speer, hornady and nosler have nothing in them about this. Thanks for the info.
     
  5. AR Hammer

    AR Hammer New Member

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    The extra pressure comes from the military using a 'Ball' powder instead of the IMR 'stick' or extruded powder Remington intended when they homologated the .223 Rem. round with SAMMI.

    The military didn't have to check with, or register with SAMMI when they decided to make changes to the powder for their rounds...
    And they didn't check with Arma-Lite/Colt or anyone else either!

    The use of that ball powder is the reason for the AR-15/M-16 early reputation for jamming and undependability.
    The early rifles were designed for .223 ammo, and the military ran 5.56x45mm ammo through them...
    The ball powder gave a little more muzzle velocity and added to the long range accuracy,
    Something the military wanted then, and is still looking for today... Accurate long range rifle fire.

    An adjustable gas rate tube is a good idea of you are going to fire both types of ammo, (along with using a 5.56x45mm rated barrel~).
     
  6. fmJK-47

    fmJK-47 New Member

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    the 556 has a thicker brass for durability, this increases the pressure of the military round over the civil. 223 Remington
     
  7. ranger_sxt

    ranger_sxt New Member

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    http://www.ammo-oracle.com/body.htm#diff