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Thread: 5.56 vs .223 pressures

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    5.56 vs .223 pressures

    I'm having a devil of a time srcounging up this information. I think SAAMI changed their website and I have not been able to figure out where this info is located.
    I have read several threads on 5.56 vs .223, but have not been able to find an authoritative source on the difference in pressures between the two rounds. I have found folks saying they differed by so much, etc. but without citing any documentation, such as a reloading manual or SAAMI. (They very well may be right, but I prefer solid documentation.)
    Basically what I am wanting to know is if anyone has a link to the safely allowable range of pressures (in p.s.i.) for a .223 chamber and the same information for a 5.56 chamber from an authorative source.
    Thanks in advance.
    PS I should add that the reason I need the information is because I am arguing with someone about how safe it is to fire 5.56 in a .223 chamber and they are insisting that there is no difference between the two rounds. I have told him that there are higher pressures in the 5.56 round and that this is what makes it unasfe to fire 5.56 in a .223 chamber. I need some "proof" to convince him. If it was just some Joe Schmoe, I wouldn't care if they were being blockheaded, but this is a family member, so I have more of a stake in convincing them.
    Last edited by Cincinnatus; 05-26-10 at 12:24. Reason: Addendum

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    Look at page 7 of the SAAMI technical data sheet unsafe firearm-ammunition combinations. It doesnít have the data you are looking for but it clearly states not to use 5.56mm in a .223
    http://www.saami.org/specifications_...mbinations.pdf

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    Quote Originally Posted by 5pins View Post
    Look at page 7 of the SAAMI technical data sheet unsafe firearm-ammunition combinations. It doesnít have the data you are looking for but it clearly states not to use 5.56mm in a .223
    http://www.saami.org/specifications_...mbinations.pdf
    Yeah, I saw that and it's good info, but I still want to find the actual pressure info too.
    Thanks.

    ."It is my duty to leave nothing undone that I may lawfully do, to pull down this administration... They who, from indifference, or with their eyes open, persist in hugging the traitor to their bosom, deserve to be insulted... deserve to be slaves, with no other music to soothe them but the clank of the chains which they have put on themselves and given to their offspring."
    --John Randolph of Roanoke (In reference to the John Quincy Adams admistration of 1826)

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    It's difficult to make a direct comparison of SAAMI 223 Remington pressures and mil-spec 5.56mm pressures because different methods are used to measure the pressures of the two cartrdiges. However, Ned Christiansen has posted some very interesting data on the subject:

    ". . . As case in point, I fired XM193 5.56 ammunition in a 223 test barrel with average pressures (conformal transducer) of 72,550 psi, and peak pressure registered at 76,250 psi. . ."

    Since the SAAMI MAP for the 223 Remington is 55,000 PSI, that puts XM193 fired from a minimum spec .223 Remington chamber at 17,550 PSI over the SAAMI MAP.
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    Thanks for the info. It helps and I appreciate it.

    ."It is my duty to leave nothing undone that I may lawfully do, to pull down this administration... They who, from indifference, or with their eyes open, persist in hugging the traitor to their bosom, deserve to be insulted... deserve to be slaves, with no other music to soothe them but the clank of the chains which they have put on themselves and given to their offspring."
    --John Randolph of Roanoke (In reference to the John Quincy Adams admistration of 1826)

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    Quote Originally Posted by 5pins View Post

    The Hornady link lists the pressures of the .223 and 5.56.
    Unfortunately, those pressures were obtained using different methods, so they are not an apples to apples comparison.
    Last edited by Molon; 05-27-10 at 16:47.
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    In my mis-spent youth I reloaded some 5.56 hot enough to drop primers.


    Has he shot any 5:56 in his 223? I would like to read the one fired brass and see if is a problem for him in his gun.


    If this is a theoretical discussion, he might be right depending on the manufacturer. Some makers are making one load and putting different lables on it.
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    The newer Ruger Mini-14's, except for the target version, are chambered for 5.56, and I believe it says .223 on the rifle. The manual also states both 5.56 and .223 can be fired from this gun. Iím about to purchase one, and I already have a stockpile of both .223 and 5.56.

    What Iíve heard is that if your rifle is chambered for 5.56, you can shoot .223. However, if your rifle is chambered in .223, you should check with the manufacture, or your manual before firing 5.56. Not all .223's can safely fire 5.56.

    NATO cartridges are loaded 10% more pressure than standard loads, but since there is a slight difference in the .223 case and the 5.56 case, there might not be a direct comparison available.
    Gary
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    Quote Originally Posted by wingspar View Post

    NATO cartridges are loaded 10% more pressure than standard loads,
    The pressures of SAAMI rounds and NATO rounds are measured using different methods. Therefore your "10%" figure has no merit.


    Quote Originally Posted by wingspar View Post

    but since there is a slight difference in the .223 case and the 5.56 case
    There is no significant difference between 5.56mm cases and common commercial .223 cases and therefore the cases are a non-issue in the difference in pressures between the two systems. The chamber and specifically the free-bore and leade are where the significant difference lies.

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