.223 - 5.56 nato

Discussion in 'Auto & Semi-Auto Discussion' started by SPLrifleman, Feb 23, 2013.

  1. SPLrifleman

    SPLrifleman New Member

    I'm new to the ar I'm told I can load and shoot each without a problem but since I don't know what the differences are in the to I'm not just gonna grab some ammo and fire it
  2. rjd3282

    rjd3282 New Member

    There are those that say you can't shoot 5.56 from a 223 chamber. Personally I haven't had anyone explain it to me that makes sense. Some say 5.56 is loaded hotter than 223 but if you look you can find 223 ammo that is faster than 5.56 ammo with the same bullet. Only one way to do that and that's add more powder/pressure. Dimensionally it is the same ammo. Then there are some that say 5.56 uses thicker brass but after extensive testing myself, the two cases weigh exactly the same. Both hold the same amount of water. Then there's the people that say the 223 chamber has a shorter throat and it causes the 5.56 ammo to spike pressures. Again demsionally the same so if it doesn't spike with 223 ammo I don't know how it will spike with 5.56. Also many reloaders adjust the OAL to get the bullet closer to the lands to make it more accurate. I guess they shouldn't do that? The only thing I've ever seen different between 5.56 and 223 is they crimp the primers on the nato stuff.

    Flame away. :)

  3. c3shooter

    c3shooter Administrator Staff Member

    We have talked this over several times here. In a nutshell-

    They are similar, not the same- just as 7.62 NATO and .308 Winchester.

    The 5.56 is loaded a bit hotter, but the real difference is in the chamber. In some cases, it can be unsafe to shoot 5.56 in a rifle marked .223. The .223 has a tighter chamber. You can shoot .223 ammo in a 5.56 rifle, but not 5.56 in a .223 rifle.

    Exception- there is a chamber called .223 Wylde that goes either way. And Ruger firearms are made to go either way, even if it says .223.

    For those that say "I've been doing this for X number of years, and I ain't never had no problems...." That's nice. I am repeating what the makers of YOUR rifles and YOUR ammo said. Argue with them- but move down to the end firing point away from other folks.

    BTW, the 7.62 NATO/ .308 is the opposite of this- do not shoot .308 in a 7.62 NATO gun.
    Last edited: Feb 25, 2013
  4. Donn

    Donn Active Member

    In addition to what C3 said, I understand the other difference is in the barrel. 223 is a 1/7 twist, 5.56 NATO needs 1/9.
    Last edited: Feb 23, 2013
  5. JonM

    JonM Moderator

    Military m16/m4 have 1/7 twist barrels early m16a2 had 1/9 and m16 and m16a1 were 1/12.

    Civilian bolt guns in 223 tend to be 1/12 and very rarely are 1/9 or 1/7.

    Most milspec ar15 makers produce barrels in 1/7.

    Some companies use 1/7 1/8 1/9 twist on both 556and 223. Caliber is not an indicator of twist rate.

    The reason that 556 and 308 are different is the chambers have longer leads on the rifling in both cases its to utilize bullets that are over long in ogive. In 308 its to allow usage of 180 grain bullets and in the case of the 556 its use tracer and ap rounds which can be longer than standard 556 bullets.

    If you stick a longer bullet into a shorter lead chamber the bullet can hit the lands and grooves of the rifling this causes an overpressure situation and kaboom.
  6. bluez

    bluez Well-Known Member

    Sir, this is not correct.

    it depnds on the weight of bullet and we've gone over this.

    1/7 is the milspec because they wanted to keep the option of shooting very heavy bullets like 75gr and higher .
    But cptrary to internet rumor 1/7 it is not even neccessary for the standard 62 gr military round which is equally accurate in a 1/9 barrell.

    Personally I feel that 1/9 is perfect for our civilian purposes since it shoots 55gr and 62 gr equally well and can handle up to 69 gr someitmes more just fine.
    And in any event 55gr is the most common civlian bullet.

    1/7 is considered more prestigous by many since its the milspec..

    And of course some folks DO shoot the heavier bullets like 75 gr, 77gr etc those folks should go w/ 1/7.

    My AR's are amix of 1/7 and 1/9 BTW but since i limit myself ( for now) to 62gr and 55 gr bullets they are functionally identical to me ( 55gr also works fine in 1/7 barrells even tho theoretically it should lose some accuracy being "over stabilized")

    but all this has nothing to do with .223 vs 5.56 and c3 shooter explained that properly IMO.
    Last edited: Feb 23, 2013
  7. robocop10mm

    robocop10mm Lifetime Supporting Member Lifetime Supporter

    The 1/7 twist is actually for the tracer round which is even longer than the standard M-855 62 gr bullet
  8. bamashooter68

    bamashooter68 Member

    SPL your AR should be NATO chambered. I dont know of any that arent. If thats the case you can shoot both. I have a 1:9 twist AR and Mini-14 and both can shoot and stabilize short 75gr bullets but not the longer ones like the A-Max. It really depends on the length of the bullet.
  9. JTJ

    JTJ Well-Known Member Supporter

    If you want to take responsibility for getting someone injured it is up to you.
    Saami .223 chamber length = 2.410"
    Wylde .223 chamber length = 2.445"
    NATO .556 chamber length =2.550"
    Those are huge differences. A .223 fired in a .223 chamber will have a higher velocity than one fired in a NATO chamber because of the different pressure peak. A NATO penetrater or tracer round with their longer bullet length could be catastrophic in a .223 chamber.:eek:
  10. rjd3282

    rjd3282 New Member


    Go back and read my post. If you can find anything I said that isn't true let me know. I'm not anybody's mother let them make up their own minds about things. How would I be responsible for what other people do. It's funny, when I go to the reloading manuals there is no distinction between the two. You can't buy 5.56 dies, you can't buy 5.56 bullets it's all labeled 223 Remington, or .224 bullets. If you are going to talk about things like penetrators or tracers then be specific. I never mentioned either.

    Chamber lengths aside the actually round itself is the same length for a given bullet weight. I never said there was no difference in chambers I said there is no difference in the ammo.
  11. JTJ

    JTJ Well-Known Member Supporter

    I am not arguing about the cartridge as they are virtually identical. I use military brass for reloading and have experienced no problems. There might be differences from different mfg or runs but it is generally negligible. However the factory loads for 223 and 5.56 are different with the 5.56 being loaded to a higher pressure and special purpose bullets in some cases. There is a definite danger in using factory 5.56 in a 223 chamber especially if you dont know what bullet it is loaded with.
  12. kiabe1

    kiabe1 New Member

    5.56 is just a little tiny bit bigger than .223 so if u have a gun chambered in 5.56 shooting .223 isnt a problem but shooting a 5.56 through a .223 gun is a problem
  13. c3shooter

    c3shooter Administrator Staff Member

    From ATK/ Federal Cartridge- copy and paste-

    5.56 vs/ .223
    To ensure operational reliability, the 5.56 round is designed to operate at significantly higher pressures, namely just short of 59,000 psi (case mouth meaured) which equates to almost 62,000psi when measured via conformal transducer (as done by SAAMI).

    The SAAMI max set forth for the 223 is 55,000psi (conformal transducer).

    To facilitate operating under these higher pressures, a 5.56 cartridge case possesses a stronger web design (thicker case walls towards the head), reducing internal powder volume, an important consideration for reloaders.
    The remaining differences are found in the chambering of the weapon. A 5.56 chambered weapon differs from a .223 in the throat and freebore. A 5.56 throat is approx. 30 thousandths of an inch longer and 3 thousandths of an inch larger in diameter than a 223 chamber. In addition, the throat or “start point” of the rifling, the taper with which the lands begin, is at a lesser angle, more gradual in a 5.56 than in the .223.

    These rather small, but very important differences, allow peak pressures to drop adequately before the bullet engages the rifling and also allow for more build-up of fouling and shooting residue without impeding function.

    What does all this mean? In short, you can safely fire all 5.56 AND .223 ammunition in a gun properly chambered for 5.56. You MUST NOT fire 5.56 ammunition in a 223 rifle. 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. Continued shooting of 5.56 ammunition in guns not chambered for 5.56 will show many warning signs of over-pressure, such as flattening of primers, smearing of the head stamp, dropped primers, blown primers and pre-mature wear on extractors and bolts.

    If you disagree with that do not tell me- I am not the author. Tell the people that make the ammo.
  14. locutus

    locutus Well-Known Member Supporter



    The straight skinny from the horse's mouth!

    I hope this puts these threads to rest.

    Hey! How's 'bout putting that post in a new thread and making it sticky?:):)
  15. 70cuda383

    70cuda383 New Member

    These are both factory loaded ammo, not custom hand loads.

    5.56 on the left, .223 on the right.

    Tell me there is no difference in the ammo.:confused:

  16. EDsaid42

    EDsaid42 New Member

    I learned about these differences from my son, who has a .223 that he uses for chucks, etc. He is a detail guy and I am glad of it.
  17. Shoots2little

    Shoots2little New Member


    What are the weights of the bullets in both of those? Is one 55 and the other 62-70? That would be my first estimate. I have seen differences like that even in 9mm but made by different manufacturers and the same weight projectile. Some runs of ammo will have the bullet further into the neck than others.
  18. Tenacn2

    Tenacn2 New Member

    Pressure created when firing a 5.56 is significantly higher than a .223. Firing a 5.56 in a gun specifically designed for a .223 can cause your barrel to explode. It isn't worth the risk of destroying your gun or or the pain and suffering when you find yourself in the emergency room.
  19. Chem-man

    Chem-man New Member

    Very interesting , check out this Colt 6920 I seen today.

    Notice the box- 223 and the lower 5.56

  20. Bowhunter47

    Bowhunter47 New Member

    5.56 is a higher pressure load, and the bullet is just slightly bigger, u need a micrometer to tell