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Author Topic: .223 vs 5.56 NATO  (Read 1166 times)

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Offline flyingcircusboy

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.223 vs 5.56 NATO
« on: January 03, 2005, 01:03:28 AM »
Okay, so I feel a bit silly even asking this. I am looking to build an AR-15 type rifle. I have been looking around and have been puzzeled by being required to choose between .223 and 5.56 NATO. I have been in the Marine Corps for over six years and was always under the impression that they are the same round. Am I missing something here? FCB
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Offline Lawdog

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.223 vs 5.56 NATO
« Reply #1 on: January 03, 2005, 01:12:13 PM »
flyingcircusboy,

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Am I missing something here?


If you are then I am too.  Could be there is a problem with us leathernecks(Semper Fi brother)?  Lawdog
 :D
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Gary aka Lawdog is now deceased. He passed away on Jan. 12, 2006. RIP Lawdog. We miss you.

Offline PeterF.

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.223 vs 5.56 NATO
« Reply #2 on: January 03, 2005, 01:51:16 PM »
I believe they're the same in terms of caliber (i.e., diameter of the barrel), and the basic dimensions of the complete round is the same; but I think the "NATO" round is always made to a MIL-SPEC-type standard of propellant load, bullet type (FMJ), etc.   ".223", on the other hand, may have the same case, but can cover a variety of bullet types and weights; so you'll find .223 guns with differing twist rates.  I think Bushmaster's web site has some discussion of this.
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Offline Patriot_1776

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.223 vs 5.56 NATO
« Reply #3 on: January 03, 2005, 06:53:48 PM »
They are the same cartridge; I am led to believe that the "difference" lies in the choice you have of rifling twist rate.  The 5.56 NATO, I'm not sure, but it might be configured to have the 1:7" to properly stabilize the 62gr. FMJ-BT; whereas the "normal" 223 would have a slower twist rate, maybe 1:10" or 1:12".  But I believe that is why there is a difference.  The reason being, the "normal" 223 is used often for varmint hunting; thus, the varmint or "High Frangibility" bullets are used.  If they (varmint type bullets) are fired in the 1:7" rifling at high speeds, the bullets would literally come apart in flight because of the centrifugal forces over-stressing their lighter construction.  

-Patriot
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Offline Ramrod

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.223 vs 5.56 NATO
« Reply #4 on: January 03, 2005, 11:51:16 PM »
I believe the difference is in the chamber specs, and in the powders used. If I remember, SAMI standards for the .223 are differant than the military. The NATO ammo shows high pressure signs in some bolt guns.
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Offline insanelupus

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.223 vs 5.56 NATO
« Reply #5 on: January 04, 2005, 06:26:56 AM »
As I understand it, a match chambered .223 MIGHT chamber a 5.56 NATO, however, a .223 will always work in a 5.56 NATO.  It is my recollection, (which on occasion is flawed), that the 5.56 is just a few thousandths of an inch longer than a .223.  Therein lies the problem of trying to cycle 5.56 rounds in a .223 match chamber.  The round may not chamber, and if it does there could be a problem with pressures.  I could be mistaking in this, but I believe that is right.  The match chambers as usual seem to be the most finicky.  The mil-specs for 5.56 NATO are just slightly different than SAAMI specs for .223.
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Offline azshooter

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.223 vs 5.56 NATO
« Reply #6 on: January 04, 2005, 06:37:14 PM »
You guys are sad.  I thought everyone know about the anmo oracle :)

http://www.ammo-oracle.com/body.htm
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Offline Patriot_1776

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.223 vs 5.56 NATO
« Reply #7 on: January 04, 2005, 07:32:11 PM »
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You guys are sad. I thought everyone know about the anmo oracle


Sorry azshooter, I don't think I've heard of it before.  Thanks for posting the link, it was most informative. 8)

-Patriot
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