.223/5.56

.223/5.56

This is a discussion on .223/5.56 within the Defensive Ammunition & Ballistics forums, part of the Defensive Carry Discussions category; Please excuse my extreme ignorance, but I am just now doing research on the AR platform in hopes of buying one in the near future. ...

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Thread: .223/5.56

  1. #1
    Member Array gen3's Avatar
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    .223/5.56

    Please excuse my extreme ignorance, but I am just now doing research on the AR platform in hopes of buying one in the near future. Are .223 and 5.56 the same caliber? I mean, are they interchangeable in the same rifle? Thanks.
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  2. #2
    VIP Member Array StormRhydr's Avatar
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    Nope, not the same caliber. Heres how it works: If the gun is stamped "5.56", you can shoot either 5.56, or .223 out of it.

    If the gun is stamped .223, you can only shoot .223 out of it SAFELY. In other words dont put 5.56 in it.

    If its stamped both 5.56 & .223 (some are) it will shoot either caliber.
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    Distinguished Member Array airslot's Avatar
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    ^^^^^
    This
    The situation will NEVER BE THE WAY YOU WANT, it WILL BE THE WAY IT IS. You must be FLEXIBLE ENOUGH TO ADAPT and just "DEAL WITH IT".

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    Member Array gen3's Avatar
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    Thanks, StormRydr. That is exactly what I needed to know. I love this forum.
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    Hence, buy the 5.56, all other things considered equal.

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    VIP Member Array pittypat21's Avatar
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    For more detailed information, there are a large number of threads on this topic in the forum. What stormrhyder said is all you really need to understand for basic operation/functionality, but if you really want to understand it, you can find a large amount of information concerning the difference. However, keep in mind that while there is a large amount of information, there is a large amount of that that is inaccurate.


    By the way, there is a similar issue with .308 and 7.62x51. If a barrel is marked 7.62x51 it can only shoot 7.62x51 SAFELY, but if it is marked .308WIN it can shoot either just fine.
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  7. #7
    VIP Member Array pittypat21's Avatar
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    Somebody correct me if I'm wrong, but I believe there are a few rifles out there marked .223 WYLDE, which can also shoot both just fine.
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    Member Array TDH1961's Avatar
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    The difference in a 223 and 5.56 is in the gun only. The throat on a rifle that is 5.56 is a little deeper than a 223. 5.56 is usually loader a little hotter than 223 and has less case capacity .When Loading a 5.56 into a chamber that is for 223 the bullet is touching the rifling to start with this raises the pressure because the bullet has to build more to overcome the resistance of the bullet touching the rifling. For the 223 that pressure is more than SAAMI recommends. Hope this helps. Never be afraid to ask a question about a gun related issue. I have always said the only dumb question about a gun is the one that is never ask.

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    Member Array Ljutic's Avatar
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    I'll add that the new rage is listing "Cal. Multi" on the lower. In this case, consult the owners manual for guidance on suitability for 5.56 and/or .223.
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    VIP Member Array Kilowatt3's Avatar
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    Quote Originally Posted by pittypat21 View Post
    ...By the way, there is a similar issue with .308 and 7.62x51. If a barrel is marked 7.62x51 it can only shoot 7.62x51 SAFELY, but if it is marked .308WIN it can shoot either just fine.
    Technically true, but not a fair comparison!

    A 5.56 NATO is, by spec, loaded considerably hotter than a .223. This, combined with the difference in the chambers (i.e. the leade length) can cause the pressure of a 5.56 in a .223 chamber to exceed the PROOF pressure for a .223; far exceeding the SAAMI spec pressure.

    The very hottest (in-spec) .308 round exceeds the pressure spec for the 7.62 NATO by ONE PERCENT; well within the manufacturing tolerance, and less than the typical manufacturing variation in factory ammo loadings.

    5.56 in a .223 chamber is FAR more likely to cause a problem than .308 in a 7.62.
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  11. #11
    VIP Member Array pittypat21's Avatar
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    Quote Originally Posted by Kilowatt3 View Post
    Technically true, but not a fair comparison!

    A 5.56 NATO is, by spec, loaded considerably hotter than a .223. This, combined with the difference in the chambers (i.e. the leade length) can cause the pressure of a 5.56 in a .223 chamber to exceed the PROOF pressure for a .223; far exceeding the SAAMI spec pressure.

    The very hottest (in-spec) .308 round exceeds the pressure spec for the 7.62 NATO by ONE PERCENT; well within the manufacturing tolerance, and less than the typical manufacturing variation in factory ammo loadings.

    5.56 in a .223 chamber is FAR more likely to cause a problem than .308 in a 7.62.
    Thanks for the clarification!


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    Distinguished Member Array brocktice's Avatar
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    Unless you get something high-end like BCM I strongly recommend you find a gunsmith with a Michiguns gage and reamer and have your 5.56 barrel checked, if you get one. My S&W M&P-15 was not correctly chambered despite being stamped 5.56 and I got one popped primer despite not shooting very many 5.56 rounds at all. All fixed now.

    http://www.m-guns.com/tool_new.php?product=gage
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    Member Array ZacMan1987's Avatar
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    Quote Originally Posted by Ljutic View Post
    I'll add that the new rage is listing "Cal. Multi" on the lower. In this case, consult the owners manual for guidance on suitability for 5.56 and/or .223.
    The lower makes no difference. The lower can be stamped tacticool explosive zombiebane caliber. It won't be an issue. The place to go for the end-all answer is the barrel, because that's all that matters. The lower can say .223, 5.56, Cal Multi, it really doesn't matter.

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    Member Array ZacMan1987's Avatar
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    Quote Originally Posted by brocktice View Post
    Unless you get something high-end like BCM I strongly recommend you find a gunsmith with a Michiguns gage and reamer and have your 5.56 barrel checked, if you get one. My S&W M&P-15 was not correctly chambered despite being stamped 5.56 and I got one popped primer despite not shooting very many 5.56 rounds at all. All fixed now.

    Michiguns Ltd. - AR-15 Tools and Accessories
    I have seen you post this twice in the past week. You''re the only person who I have ever read about having this problem. How much time did you spend working w/ S&W before you had your chamber reamed? If it was truly a .223 chamber, why not just get your $$$ back from them or get them to provide a properly made barrel?

    I'm not saying you're wrong, but I am saying you're 1 in a million. Saying that EVERYBODY should spend $50+ to check their chamber based on this experience is more than a little alarmist.

  15. #15
    Distinguished Member Array brocktice's Avatar
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    Quote Originally Posted by ZacMan1987 View Post
    I have seen you post this twice in the past week. You''re the only person who I have ever read about having this problem. How much time did you spend working w/ S&W before you had your chamber reamed? If it was truly a .223 chamber, why not just get your $$$ back from them or get them to provide a properly made barrel?

    I'm not saying you're wrong, but I am saying you're 1 in a million. Saying that EVERYBODY should spend $50+ to check their chamber based on this experience is more than a little alarmist.
    I was having other work done on the gun locally and it was easily checked and fixed. Several other people in my area had the same problem with various other brands including Colts. It's not an isolated issue.

    EDIT: Read this. If you like, use search in your browser to jump to " But my barrel is marked 5.56, I canít have a problem"

    http://www.murraysguns.com/223vs556.htm

    Also I don't suggest everyone buy the gage and the reamer, but find a good AR smith that has them.

    If it's a range toy I guess it doesn't matter, but if you plan on using the gun for SD/HD, it could stop the rifle when you need it most. I've been posting it where appropriate because I think it's an underappreciated and important issue, and might have been made worse by the buying frenzy over the last year.

    I've seen a popped primer stuck in a gas key at a carbine class, it stops the gun hard.
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