.223 Remington vs. 5.56 NATO

Discussion in 'Technical Questions & Information' started by Marlin, Feb 15, 2011.

  1. Marlin

    Marlin *TFF Admin Staff Chief Counselor*

    I thought this article from today's Human Events Daily Newsletter worth all of us seeing. It has some good advice for being sure you are safely shooting.


    .223 Remington vs. 5.56 NATO: What You Don’t Know Could Hurt You
    by Richard Johnson
    Posted 02/15/2011

    Is firing a 5.56 NATO cartridge in your .223 Remington chambered AR15 dangerous? Or do Internet forum-ninjas and ammunition companies selling you commercial ammo instead of surplus overstate the dangers? Believe it or not, a real danger exists, and some gun owners who think they are doing the right thing may not be safe.

    The Cartridges

    The .223 Remington and 5.56x45 NATO cartridges are very similar, and externally appear the same. But there are some differences that lie beneath the surface.

    The 5.56 case has thicker walls to handle higher pressures, meaning the interior volume of the case is smaller than that of a .223. This will alter the loading data used when reloading 5.56 brass to .223 specs.

    Some 5.56 loads have a slightly longer overall length than commercial .223 loads.

    The Chambers

    The significant difference between the .223 Rem and 5.56 NATO lies in the rifles, rather than the cartridges themselves. Both the .223 and 5.56 rounds will chamber in rifles designed for either cartridge, but the critical component, leade, will be different in each rifle.

    The leade is the area of the barrel in front of the chamber prior to where the rifling begins. This is where the loaded bullet is located when a cartridge is chambered. The leade is frequently called the “throat.”

    On a .223 Remington spec rifle, the leade will be 0.085”. This is the standard described by the Sporting Arms and Ammunition Manufacturers’ Institute, Inc. (SAAMI). The leade in a 5.56 NATO spec rifle is 0.162”, or almost double the leade of the .223 rifle.

    A shorter leade in a SAAMI spec rifle creates a situation where the bullet in a 5.56 NATO round, when chambered, can contact the rifling prior to being fired. By having contact with the rifling prematurely (at the moment of firing), chamber pressure can be dramatically increased, creating the danger of a ruptured case or other cartridge/gun failure.

    The reverse situation, a .223 Rem round in a 5.56 NATO gun, isn’t dangerous. The leade is longer, so a slight loss in velocity and accuracy may be experienced, but there is not a danger of increased pressures and subsequent catastrophic failure.

    How serious is the danger of firing 5.56 ammo in .223 guns? Dangerous enough that the SAAMI lists 5.56 military ammo as being not for use in .223 firearms in the technical data sheet titled “Unsafe Firearm-Ammunition Combinations.”

    ATK, the parent company of ammunition manufacturers Federal Cartridge Company and Speer, published a bulletin entitled “The Difference Between 223 Rem and 5.56 Military Cartridges.” In this bulletin, ATK stated using 5.56 ammo in a .223 rifle could result in “…primer pocket gas leaks, blown cartridge case heads, and gun functioning issues.”

    However, the danger may be lower than SAAMI or ATK suggest. In Technical Note #74 from ArmaLite, the company states “millions of rounds of NATO ammunition have been fired safely in Eagle Arms and ArmaLite’s® SAAMI chambers over the past 22 years,” and they have not had any catastrophic failures.

    According to ArmaLite:

    “Occasionally a non-standard round (of generally imported) ammunition will fit too tightly in the leade, and resistance to early bullet movement can cause elevated chamber pressures. These pressures are revealed by overly flattened primers or by powder stains around the primer that reveal leaking gasses.”

    What Do You Have?

    So, if you own a rifle chambered for the .223 for 5.56, do you know for which caliber it is really chambered?

    Many match rifles are chambered in .223 Remington (SAAMI specs) for tighter tolerances, and theoretically better accuracy.

    Many of the AR-15’s currently sold on the market are made for the 5.56 NATO cartridge. If you own one of these, you should be fine with any .223 or 5.56 ammunition.

    However, ATK dropped this bomb in the bulletin on the .223/5.56:

    “It is our understanding that commercially available AR15’s and M16’s – although some are stamped 5.56 Rem on the receiver – are manufactured with .223 chambers.”

    So, even if your AR is stamped 5.56, is it really? Check your owner’s manual or call the company directly and make sure you get an answer you feel comfortable with.

    As if the confusion regarding the .223 vs 5.56 chambers wasn’t enough, there is a third possibility in the mix, that is being used by at least one major manufacturer. The .223 Wylde chamber is a modified SAAMI-spec .223 chamber that allows for the safe use of 5.56 NATO rounds, but maintains tighter tolerances for better accuracy.

    Yeah, yeah… What’s the bottom line?

    Here’s the bottom line. If you want to follow the safest possible course, always shoot .223 Remington ammunition. The .223 Rem cartridge will safely shoot in any rifle chambered for the .223 or 5.56.

    If you want to shoot 5.56 NATO rounds, make sure you have a rifle designed for the 5.56 military cartridge. Shooting 5.56 in a normal .223 Rem rifle can result in bad things.

    Richard Johnson is the co-owner of GunsForSale.com.

    © 2011HUMAN EVENTS. All Rights Reserved.
  2. GunHugger

    GunHugger Well-Known Member

    Jul 18, 2007
    SW PA
    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.

    And, many manufactures, i.e. Rock River Arms, Larue Tactical and others run a Wylde chamber.

    The .223 Wylde chamber was designed as a match chamber for semi-automatic rifles. It will accommodate both .223 Rem and 5.56mm NATO ammunition. It is relieved in the case body to aid in extraction and features a shorter throat for improved accuracy.

  3. Jim K

    Jim K New Member

    Dec 6, 2009
    "where the bullet in a 5.56 NATO round, when chambered, can contact the rifling prior to being fired."

    So how come generations of target shooters had their barrels made and seated bullets out specifically to do just that? There may be a danger of some kind, but I don't believe that is the problem.

    FWIW, at that pressure, a bullet acts like silly putty and will conform to whatever shape it has to and it will do so without any significant pressure increase. I don't think anyone is actually deliberately lying, but there is more to that story than seems to be known. I wonder how much testing they really did before jumping to that conclusion.

    FWIW, here is another take. The first thing pressure in a bottle neck rifle cartridge does is to expand the case neck as far as the chamber throat will let it. This leaves the bullet, stationary due to its own inertia, floating in a stream of gas as the gas rushes past and into the barrel. That gas, moving very fast due to the constriction, is what causes throat erosion. But it also, by escaping, lowers the total pressure.

    Now, the bullet begins to move and is forced into the barrel, engaging the lands and sealing the hole. BUT, if the bullet is already in the barrel touching the lands, very little gas will get past it and the pressure will not be relieved. So the problem may not be that the pressure increases because the bullet is touching the lands; it may be that the pressure is not relieved as it would be if there were more leade.

    Maybe essentially the same thing, but I feel the people involved have simply resorted to a simplistic answer. It might be right, but I don't feel they really understand what is involved.

  4. GunHugger

    GunHugger Well-Known Member

    Jul 18, 2007
    SW PA
    Jim, I'm an old target shooter. You are talking about a bullet and a chamber made for each other. Shooting a 5.56 round in a .223 chamber is not the same thing, they aren't a match.

    The primary difference between .223 Remington and 5.56 x 45 mm is that .223 is loaded to lower pressures and velocities compared to 5.56 mm. .223 Remington ammunition can be safely fired in a 5.56 mm chambered gun, but the reverse can be an unsafe combination. The additional pressure created by 5.56 mm ammo will frequently cause over-pressure problems such as difficult extraction, flowing brass, or popped primers, but in extreme cases, could damage or destroy the rifle. Chambers cut to .223 Remington specifications have a shorter leade (throat) area as well as slightly shorter headspace dimensions compared to 5.56 mm "military" chamber specs, which contributes to the pressure issues.

    Last edited: Feb 15, 2011
  5. Jim K

    Jim K New Member

    Dec 6, 2009
    So which is the problem, higher pressure in the 5.56 or the short leade in the .223? Both? Something else? I am willing to be educated, but the symptoms you describe are not signs associate with either a short leade or a somewhat higher pressure, they are signs of extremely high pressure, in the 100k+ range, just short of complete case failure.

    The info I have shows the .223 max average at 55,000 psi; even if the 5.56 goes 60k or more, it should not create those problems.

    I have no idea what could cause those pressures, but I have fired hundreds of rounds of 5.56 spec ammunition, USGI and other, in several .223 chambered rifles with no such signs. (Do you really believe a short leade or a 10% increase in pressure will cause a Remington 700, one of the strongest rifles in the world, to blow up??)

    Have you seen or experienced those problems yourself, or are you just quoting others? If you have personally experienced those problems, what rifles and ammuntion were involved, factory or handloads? If handloads, were they your own, or others'?

  6. polishshooter

    polishshooter Well-Known Member

    Mar 25, 2001
    No, the problem is NOT so much for Bolt action rifles, but the AR series. What guy with a target .223 would shoot NATO in his target/varmint gun anyway? Nobody I know with a .223 varmint gun would even consider it.

    The 5.56 Nato rounds are military "blasting" or "Practical" 3 gun practice ammo for ARs, period. Meant to be fired a lot more probably in one day than a target guy would put down his B/A in 6 months or a year!

    And do YOU want to take the chance that ALL "Nato spec" ammo loaded in the US, UK, Portugal, Germany, Russia, Spain, South Africa, Israel, Korea, Japan, etc, etc, etc is loaded to the same specs? Or do you want to maybe stick to Hornady, Remington, Winchester NOW for your Model 700?

    I have a buddy that specifically loads his .223 for his varmint Model 70 as you describe...purposely seating the bullet out with no crimp so it "seats itself" when you close the bolt. BUT he has a sled and loads SINGLY. And when done you have to unload through the muzzle, or the bullet will stick in the rifling (I know, before he explained that to me I stuck one in South Dakota last year making the rifle safe...:eek: Thats another story, especially when we discovered that all THREE of us left our cleaning rods in the hotel from cleaning our rifles the night before!:eek: I have a neat photo of a buddy slamming the butt of that EXPENSIVE rifle on the ground to get the bullet out:p)

    NO magazine rifle, B/A or otherwise , much less a semi auto with a 30 round mag would be loaded without a crimp because of the recoil, and in any event, the OAL of such a cartridge would not FEED from a mag.

    You want to shoot NATO ammo, get either a NATO or Wylde chamber. I am thinking of getting a Varmint upper for my RR rifle this summer, and even for that I am getting a Wylde chamber.

    The difference between the two granted is not as much as the difference between .308 Winchester, and the 7.62 Nato rounds, but there IS a difference.
    Last edited: Feb 16, 2011
  7. polishshooter

    polishshooter Well-Known Member

    Mar 25, 2001
    And the difference in accuracy is not much at all if you look at it from the "Tactical" AR side...my Nato chambered Rock River 16" HB with the Bushnell 3x9 I have on it for varmint work will ALMOST do 1" from a bench with Black Hills .223 ammo. The Federal X193 and PMC 5.56 cheap ammo will do between 1 1/2" and 2 1/2" from a bench. which is still tremendous for a "tactical" rifle.

    From the Varmint/Target side. a .223 or a Wylde chamber HB 20"+ free floated with a good scope will do 1/2" to 3/4". Some guys claim less, but from the guys I know with them that is what they get. A good bolt action varmint can do less, I've seen that as well.

    I would love to hear if anybody out there has a true Varmint AR with a 5.56 chamber what results they get firing good .223 ammo. I don't know anybody with a varmint AR that does NOT have a .223 chamber though.
  8. now to add to the confusion,the 47th edition of the lyman catalog states the 223 as the armed services ammo with no distinction one way or the other about the 5.56 or 223 old semperfi
  9. Jim K

    Jim K New Member

    Dec 6, 2009
    This is beginning to sound more and more like baloney and BS. First, there is a clear statement that firing 5.56 in a .223 rifle is dangerous due to the different leade. Then that is forgotten and there is another clear statement that the 5.56 is of much higher pressure and will damage a .223 rifle. Then there is a statement that that only happens in AR-15 type rifles. When I mention firing 5.56 in a .223 Model 700, I am told, not that it is dangerous, but that no one would ever do such a thing. (Why not, I ask?)

    Then I am told that there is no problem with a bolt action because not enough rounds will be fired. (What does that have to do with it?) Then that a large capacity magazine is to blame. (Again, what could the magazine capacity have to do with the pressure of the cartridge?)

    Then, I am told that someone "loads his .223 for his varmint Model 70 as you describe...purposely seating the bullet out". In other words exactly the "bullet seated touching the lands" that is supposed to blow up rifles, apparently does not blow up Model 70's either. But surely the swelled case heads and leaking primers would happen on a bolt rifle also. Or do these awful things happen only to AR rifles? Why? Are they so weak they fail from even moderately high pressure which bolt guns take in stride? And if AR rifles are weak, why would ammunition designed for them have higher pressure than ammunition intended for bolt actions? A bit of a conflict, there, folks!

    Then I am told about accuracy problems. But no one mentioned accuracy; the whole discussion is about danger, swelled case heads, flattened primers, blown up guns. Where did all that go to? Conveniently forgotten as soon as some one chooses to doubt it?

    Sorry folks. I'll buy any logical, tested, problems. But what I hear is a lot of conflicting stories from folks who seem not to have personally experienced any of the failures they describe so graphically.

    As for blowing up rifles because the bullet doesn't have a head start, I note that Hatcher once blocked the barrel of a Springfield rifle so the bullet couldn't move at all, and I have done the same thing with a 1911 pistol. What happened when the guns were fired? Nothing.

    Last edited: Feb 16, 2011
  10. polishshooter

    polishshooter Well-Known Member

    Mar 25, 2001
    Funny, I HAVE seen more than one .45 come apart with a blocked barrel, (stuck bullets, when guys were practicing, and once on a guy in a match, when they fired a round with no powder and the primer pushed the bullet into the barrel, and they jacked another round in behind it thinking they just had a simple malfunction, and fired another round after it. )it blows the grip bushings out of the frame and the grips into the hand, and the magazine out the bottom and probably COULD injure your hand severely, although in the times I have WITNESSED it the injury was negligible, but it DID ruin the rest of the day for them. IT is MUCH worse when it happens with a polymer framed pistol, therre are pictures all over the net of early Glocks that went to pieces, most of the time WITHOUT astuck bullet or blocked bore.

    Granted, I myself have fired my .45 with the bore blocked with mud during the 1985 IPSC Sectionals when I went through the tunnel in the assault course after a gullywasher and fell face first into the mud diving through it and buried the pistol. It fired fine but blew mud all over the place.

    This was all over the course of my IPSC career, from about 1984 to 1989.

    Always it was a guy with a stuck bullet that didn't realize it when he fired the next round...

    And I saw it happen last year at the range with a guys PA-63 too, that wasn't pretty when that let go.

    Jim, maybe I need to be more specific, or maybe you need to read more slowly without preconcieved notions...but the RECOIL forces on the rounds in the magazine is why you would NOT load UNCRIMPED bullets in ANY magazine rifle, bolt action or Semi auto. Guys who DO custom load their bullets to touch the rifling in their custom Bolt Guns do NOT crimp them, so it SEATS the bullet to the PROPER length for the chamber! In other words the bullet MOVES back into the case! A HEAVILYCRIMPED NATO Military round, crimped so the bullet would not move back and forth in the MAGAZINE under recoil, and would either get slammed back INTO the case, or get slammed OUT of the case (meant to fire through Semi Autos and Fully Automatic rifles which would MALFUNCTION if EITHER was to happen, but would probably not feed through a B/A magazine EITHER since they start out over the maximum OAL for the cartridge) would NOT "seat" itself, and therefore a longer than chamber dimensions round would force itself INTO the rifling Leade a HECKUVA lot harder than an uncrimped one that actually MOVES back into the case as the bolt is locked home. Which is why that technique ONLY works for SINGLE SHOT rifles, or rifles only fired as a single shot regardless of whether it has a magazine. I plan to load my Ruger Swift the same way, which is why benchrst or varmint guys use a SLED to turn their magazine guns into single shots ...DO you get it NOW?

    The part about feeding from MAGAZINES is that any round INTENTIONALLY loaded long to "seat itself" would be TOO LONG to feed from MOST magazines, internal or otherwise, but DEFINITELY not in an AR which has a sharply defined OAL in order to FIT into the magazine at ALL, and the bullets are heavily crimped, much more so than .223 factory rounds, which is ANOTHER pressure consideration for you.

    NATO ammo is NOT used by any guys that I know with expensive varmint/target bolt guns. You may know different guys, who just want to save a buck and don't care about the results they get from their rifle, but what really is the point? You want benchrest ACCURACY, or at least the best you can get for hunting, which you will probably NOT get with NATO military ammo from that B/A rifle. And you wouldn't USE FMJ military ammo for hunting anyway. And you will NOT shoot 3-500+ rounds in a DAY with it through your bolt gun, like an AR owner might. THAT is the REASON they use 5.56 ammo, to save money, $4-9/20 instead of $12-25+/20 for factory .223 ammo. The AMOUNT of rounds you fire does NOT matter in the least with this argument about the difference int he two rounds, it only explains the reason people shoot 5.56 in their ARs, but why people DON'T generally fire it in their Remington, Winchester or Savage B/A .223s. COST per round vs. ammo expenditure vs expected results. IT is MUCH different between the disciplines.

    And as per accuracy, ANY rifleman knows that a TIGHTER chamber with PROPERLY matched cases/rounds will GENERALLY mean better accuracy. Maybe somebody out there has a "sloppy" chamber and claims to get phenomenal accuracy, but THAT is usually "Baloney and BS"

    And finally, this argument is really only applicable to AR-15s...what OTHER rifle can you buy new with a CHOICE between a 5.56 or a .223 chamber? NONE.

    ANY experienced AR-15 shooter, which obviously you are not, knows all ABOUT the difference, and finally if you read the original posting thoroughly, you would see in the very first line says "Is firing a 5.56 NATO cartridge in your .223 Remington chambered AR15 dangerous?" (Bold face mine)

    Jim, there really is a difference, and a VERY important one to anybody considering buying their first AR. After THAT they will KNOW (learn) it.

    IF you plan to shoot a LOT, and everyone DOES after they get their first AR, or plan on any practical competitions with it, you WILL shoot NATO ammo due to the cost, so get a 5.56 chamber for your FIRST AR-15. Later get a .223 upper for it if you need optimum varmint/target ACCURACY, but use only factory or handloaded.223 ammo in THAT one and have the best of both worlds.
  11. Jim K

    Jim K New Member

    Dec 6, 2009
    OK, points made, all irrelevant. You have ranted about me, but you still have not told me that YOU, YOURSELF, have blown up a gun or seen one blown up by firing 5.56 in a .223 rifle. And you have NOT explained why it is dangerous to fire 5.56 in my .223 Model 700. I am sure you are knowledgeable about target shooting but, like many target shooters, you seem to know little about rifles or internal ballistics.

    I repeat. We are not talking about accuracy. We are talking about a specific danger caused by a specific action, firing military spec factory 5.56 in a rifle chambered (throated) for .223.

    If you cannot provide information on a specific case where a rifle "blew up", and investigation by knowledgeable experts (not the gang at the gun shop) confirmed that the wrong cartridge was the sole cause, then I submit that this discussion is interesting, but just another piece of alarmist BS, with no real basis.

    As to blowing a .45 barrel, you did not read what I said. I did not say I blocked the barrel at the muzzle or at some point ahead of the bullet. I said I blocked the barrel AT the bullet in such a way that the bullet could not move at all; the block was even shaped to the bullet ogive. (Hatcher did the same with the Model 1903.) If you don't see the difference then you obviously have no idea what causes barrels to bulge or split when a bullet is fired into an obstruction. BTW, when the bullet didn't move, the slide never moved and the strain gauge I had on it never broke.

  12. 44stevenson

    44stevenson New Member

    Sep 29, 2010
    So can you reload .223 in a 5.56 shell?
  13. Crpdeth

    Crpdeth Well-Known Member

    Apr 23, 2002
    Location location

    This question may be better asked in the reloading forum, just down the page a bit... Personally I haven't started reloading .223 as of yet because I have quite a bit of XM193 left, but my answer would be yes, of course, just keep in mind that the 5.56 has thicker walls therefore I would work my load up slowly and watch for signs of excessive pressure.

    Thanks for re-posting this, Judge... It's damn good information that we should all know and understand.

  14. JohnTheCalifornian

    JohnTheCalifornian Member

    Jun 12, 2009
    I do. I use 223 dies to full length resize, and I dont load anywhere near maximum loads. All is fine. I fire them through my AR-15 "Mutt".
  15. woolleyworm

    woolleyworm Well-Known Member

    Feb 23, 2009
    SW Fort Worth
    What happened to the gases?
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