The comparison between .223 and 5.56 isn’t a new one, so there is a lot of discussions to weed through to learn about the two. You may find that you need a certain type of projectile for hunting or defense, and it may come down to the performance of each. Now right off the bat, I want to inform you that the only reason these cartridges have different labels is because there are loading differences. We must also note that in some of the chambers made specifically for the .223, the beginning of the rifling is cut sharper, which can cause some pressure issues for the rifle when using 5.56 ammo. But we will get back into this later.Ultimately, because they originated from the same cartridge, they are very similar, but that does not mean that they are not necessarily interchangeable. This article discusses three key differences between .223 Remington and 5.56x45mm NATO.
History of .223 and 5.56 Cartridges
The history of the two cartridges (5.56 and .223) really started when the military was looking for a small-caliber round that could be used in their “Individual small-caliber assault rifle” research and development project.
They started with the .222 Remington cartridge and after failing some tests, Remington redesigned the round and named the new design the .222 Remington Special. This design ended up being renamed the .223 Remington. After passing the tests for the round satisfactorily, the military adopted the cartridge under the alternative measurement designation of 5.56 NATO and has remained the same since, for the most part. In the ’60s, Remington made the .223 Remington available to the commercial market where SAAMI then established standards for the cartridge, as with all other cartridges.
Comparison of the .223 Remington and 5.56x45mm
Dimension Measurements
The 5.56 and .223 have no visible differences when you look at the two side by side, nor dimensionally in any way shape, or form. The only dimensions that would be different, would be in the chamber of the rifle you are using. At glance, the two rounds are indiscernible. Both rounds use a bullet of .224in diameter and an overall length of 2.26in. In general, the external dimensions for the two calibers are identical. What’s more significant is the pressure of the two rounds and the difference in the rifle chambering.
Pressure Measurements
One of the problems with comparing these two cartridges is that they utilize different methods of measuring pressure.
- SAAMI (Sporting Arms and Ammunition Manufacturers’ Institute) measures the .223 pressure at the center of the casing.
- NATO standard measures the pressure at the throat (or leade) of the chamber.
To rectify the two different methods, several have undertaken experiments with their own standardized recording method to compare “apples to apples.” One such thorough study was carried out and recorded in detail by Andrew Tuohy posted via Lucky Gunner Labs. Tuohy evaluated various .223 and 5.56 ammo fired through rifles chambered for .223 Remington and 5.56x45mm.
His, and the research of others, confirms that, generally, shooting .223 through a 5.56 chamber results in lower pressure, but still functions (safely). Firing 5.56 through a .223 chamber, however, results in somewhat higher pressures. Although the differences aren’t massive (~5% in the previously referenced study), the extensive firing of 5.56 through a .223 chamber could lead to over-pressure malfunctions, such as popped primers or blown cartridge case heads and other firearm malfunctions.
The case thickness is also the same unless we are talking about steel/polymer hybrid cases, which are listed as a good alternative case manufacturing material to brass that won’t cause problems despite range legend.
The difference that typically makes the .223 lower in pressure is that it is regulated by SAAMI specifications, which generally lower the pressures of projectiles all over the market. If we look at NATO and European standards, their ammo is typically loaded to higher pressures. In some cases, they would cross into the realm of +P ratings if they were to be evaluated per SAAMI standards.
For example, the 124gr 9mm NATO round typically is expected to go around 1200FPS out of the Beretta M9 Barrel (4.9″) with muzzle energy reaching up to 400FT/LB. This is in fact quite normal for the European 9mm standards. This was actually the Original and standard loading when the 9mm was first developed. Most European firearms chambered in 9mm are built to withstand these pressures as a normal diet since that is the standard pressure the 9mm is loaded to.
SAAMI specifications typically water down the energy and velocities of rounds, and the .223 Remington falls victim to this. The .223 Remington cartridge under SAAMI is loaded to about 7,000PSI lower that 5.56. This is the reason that you are advised against loading 5.56 ammo into a .223 chambered barrel.
Chamber Differences
The most important difference between .223 and 5.56 chambers is the length of the throat (or leade) for each chamber. More specifically, the leade is located at the mouth of the barrel before the rifling occurs. Comparing the NATO and SAAMI regulations, the leade for 5.56 chambers is nearly twice as long as that of a .223 chamber (.162in to .085in, respectively). If a 5.56 round contacts the barrel rifling too early, it can cause pressure spikes (leading to malfunction, and potentially damage) in the chamber. This explains why it is safe to fire .223 through a 5.56 chamber, but not recommended to fire 5.56 through a .223 chamber.
There is one thing I have noticed that the 5.56 and .223 have in common
I found that it is hard to find good self-defense ammo on the market that doesn’t have an issue in one corner or another. One round will be a shallow penetrator and not even reach the vital organs, such as the 5.56 and .223 TAP FPD and V-Max rounds by Hornady.
The other issue you will find is that the ones that will get sufficient penetration will overpenetrate or just go off course and pitch and yaw on impact with flesh or bone like the M855 and M193. The temporary wounding cavity from a rifle round can have an effect on tissue and cause damage, but its useless if it doesn’t reach the vitals in the chest cavity. The point of using a firearm for defense isn’t to wound or hurt, it is to use deadly force because all other options have been exhausted.
The only rounds that I know of that have sufficient penetration without much deviation and have good terminal performance overall is the 5.56 Speer Golddot soft point ammo. I prefer these rounds in the 64GR loading for my 16″ barrel rifles. If you use an SBR, I would opt for the 55GR variant.
Which should you choose?
As with so many elements of making a firearm purchase, the “right” option is subjective. The differences between the performances of the 5.56 and .223 are minimal but still are enough to make it a fine science to find out which one works best for you. For me, I think I prefer 5.56 when I can get a deal on it, but if not, .223 does just fine and I believe most of the AR15/5.56 rifle community would agree. Personally, I like shooting hot ammo sometimes, and the 5.56 makes great ammo for breaking in a new rifle, and as a defense loading. The .223 for me is a fun/budget practice round that can also serve as a varmint round of choice here in Alaska. Ultimately it is up to you to decide which loading you want to go with.
If all you intend to purchase are .223 Remington rounds, there is nothing wrong with getting a rifle chambered for .223. However, if you want the option of firing mil-spec 5.56 through your rifle, you may prefer picking up a 5.56 chambered AR-15. After all, you can still fire the .223 through it, safely, if you want. Price and personal preference are also factors to consider when making that decision. What works for you?
just came from shooting my older tactical 24 inch heavy bull barrel savage got it used from older cent gould not go range anymore .barrel is stamped 223 and has also wierd weight luck on muzzle end ,varminter mod stock tasco mag scope .shoot ammo did not pay attension came home and chek cartidge was shooting half inch group with 556 winchester white box when walmart still sold it but it was on different box with 223 remington .the chansed ammo for remington 223 62 grain was inch group .like i said noticed at home so maybe my rifle is good for 556 nato like some artigles stating load chansing after shooting lot ammo .this rifle been shot alot and its now so accurate with 556 go figure .
So from reading this and my understanding. You can get a 556 nato rifle and fire 223 all day with out any issues?
the difference between a 223 and a 556 is the throat angle length…
556 freebore .056
223 freebore .025
difference .031
amount of thorat growth after 800 rounds of 223, .030+
congrats…. your 223 is now a 556…
You will also notice you won’t find 1 pic of a 223 that blew from a proper 556 round anywhere on the net… there’s good reason for that…. it wont happen…
You should really explain the whole “magazine” issue before jumping ahead to the “push another brand new clean and shiny bullet into the “hole”” part. I don’t think one should skip that page in the sequence..
The head stamp on the case should tell you where it came from.
Have 100 or so spent brass in .223 & 5.56. I want to reload them but I need to tell which round came out of which case. Anyone know how to tell them apart?
Same factors are involved w/ 7.62 N and .308 Win……
More importantly by going with 5,56 one can use any 5.56 or .223 brass includeing milsurp for reloading which is real important when using a progressive press as one you have you brass prepped meaning the primer pocket crimps gone you are good to go at cranking out ammunition.
….chamber for .223 Wylde, easy enough……especially if you like the heavies.
KathyCat You seems you have answered your own question and survived in tact. It seems the “hole” that you have in your AR-15 or whatever surely fits only one “bullet” at a time without most probably stretching or even ripping the “hole” wide open causing serious even irreparable damage to the “hole”. For your own safety Ms. KathyCat I would only put one (1) bullet in the “hole” at a time and that way by squeezing the trigger on your AR-15 OR whatever, you will get a big bang which will automatically remove the old used bullet from the “hole” and push another brand new clean and shiny bullet into the “hole” so as to safely get another big bang…
Maybe you’d have better luck using 2 of the 23 rounds.
Shes gotta be a obama/Hillary fan!!!!
Keep trying g it’ll work some day! By the way how many kids do you have?
I too have the carbon 15 and have taken lots of chucks and two whitetail deer with it. I load .224 diameter polymer tip hornady Bullets. They are awesome performers and drop deer like my ’06 but admittedly, you need a well placed shot to drop ’em in their tracks. It’s a great lightweight rifle and investment in a .22 LR conversion is well worth it. It performs great in the carbon platform.
KathyCat try looking down the barrel that might solve the issue.
KathyCat Come on, Hillary. Everyone knows you put the barrel end in your mouth and suck on it as you load the bullets. But don’t pull the trigger in this position and don’t slam the butt end on the ground. You may want to coat the barrel end with Old Log Cabin to give it a maple flavor while you load.
casey When reloading your own ammo your bullets are 22 /224 for a 223. This is probaly what your husband meant. He is correct.
The problem is, you have to buy “AR15” ammo. Its hard to find but just keep asking.
KathyCat it’s easier to load 5 at a time through that hole if the butt of the weapon in on the ground and the barrel is braced against your shoulder. Works like a charm! Give that a try.
IsaacBarden casey That is what I was gonna say is probably talking about diameter.. i.e .223-224
KathyCat Don’t give up you day job.. leave the comedy to the professionals…
You must be joking?
KathyCat Take your rifle back to whoever sold it to you and get your money back. You are too stupid to own a firearm.
KathyCat Try clamping them together then smackem with a big hammer
Just a troll, ignore.
KathyCat lady please tell me that you are kidding
Maybe somebody can help me, I just bought my first AR 15 or whatever and it says on the barrel 5.56 and I haven’t been able to find bullets that just say 56 but I did find some that did say 5.56 but I can’t get 5 of them in the barrel at the same time, I put one in the hole where the bullet goes and then try and put the second one in there and it doesn’t seem to fit so I hit the charge handle thing real hard trying to force the second one in and it fires one time every damn time and I almost shot my foot off the first try so before I try it again how the hell do you get 5 of these 56 bullets in the barrel at the same time?
I’m beginning to believe that the difference between the two cartridges is that the .223 Remington is the 55 grain projectile M-193, and that the 5.56mm NATO is the 62 grain projectile SS-109/M-855. That and the military’s specifications to the chamber dimensions.
RoyTaylor What you captured were probably a couple of ex-ARVN Colt 601s or 602s (early M-16s). I carried some early M-16s with XM-148s attached to the barrel as a Security Policeman in the USAF at Clark AB RP in 1988-1990. The early rifles had nothing stamped on them about being and M-16 they were just stamped AR-15, the caliber was stamped .223 Remington. To tell if it is an early rifle it will have a slick sided right side of the lower receiver, it will not have a protective fence around the mag release, nor the raised surface above it. The bolt hold open device will lack the raised nipple of later rifles and the upper receiver will be slick sided as well with out the forward assist. For the ammo I cannot explain that.
In 1971 I Captured Two VietCong armed with civilian modal AR 15s and .223 Ammo, which can be fired from any 5.56 Simi Automatic Only. Attempting to Shoot .223 ammo On Fully Automatic Mode Military M16 ,can cause your AR15M16 to jam OR Explode in your face
Never knew there was a difference between them. I have fired both through my rifle without a problem. I prefer the AK and my M1A, but that is from being a Marine in Vietnam. I still dislike any variation of the M16. I know they have fixed all the problems, but I like weapons that will work even if dropped in mud.
I can personally account that I have shot thousands of military 5.56 rounds through a 223 and have not had one sign of any problems. In theory all sorts of things can happen. If you would actually look and see what the max chamber pressures are measured at the same point and testing basis. You would see that it is negligible at best. People should be more concerned about proper maintenance then with .223 or 5.56.
AlbDavidT SavageHenry 5.56 for the same projectile weight will be faster than a .223, as the 5.56 is loaded hotter. Higher weight projectile = lower speed in same caliber, but heaver also = more retained energy down range! 5.56 offers more options, you also have to consider the twist rate of your barrel, faster rate is better for light projectile, slower rate is better for heavy projectiles.
Dawoogie Yep, I have several Oly Arms barrels, all stamped 5.56.
Jackhunter If the barrel is stamped .566 your rifle would fall under a multi caliber build, which is safe to shoot .223 and 5.56, alike.
My Colt has .223 stamped on the receiver and 5.56 NATO stamped on the barrel. I think it is a 5.56. Is that correct?
Is it .223 wylde? If so it will shoot both
2013gs4lt
After everything I’ve read online and people I’ve asked,say NO.
If the barrel was stamped 5.56, I’d say Yes.
I would ask to talk to someone else at the manufacture that is in a top position and have them email you something backing that they guarantee it will fire both, in writing.
I have a manufacture who sells an AR15 in .223 but on the phone says it can fire 5.56 and has been tested. They say the chamber is a modified on so it can digest both without an issue. Should I take their word for it and shoot 5.56 or just stay with .223 ammo?
drmorris9 FateofDestinee SavageHenry .223 produces lower pressures.
IsaacBarden casey
casey What he means is that the diameter of the bullet is the same. If you shot a piece of paper with .22, .223, and 5.56, all three holes would look the same.
So my husband kept saying that 22 ammo 223 ammo and 556 ammo are the same. I had someone ask about 22 ammo and my husband said that 223 and 556 are 22. that didnt sound right so im trying to clear it up so i understand better. i have been researching the difference between these two and this was the most helpful information i have found yet. So what about the 22 ammo. Is that the same? can you us 223 and/or 556 in a 22 long rifle. Thank you to anyone who can explain
this a little better for me.
FateofDestinee Nate226 So whatever is stamped on the upper on the actual rifle is what you shoud go by. My AR15 only says .223 on it, so that is what I should shoot… Great article.
Slowcala You have a 5.56 chamber (the lower doesn’t matter within a caliber family). You may shoot 5.56 or .223 in that chamber without undue wear (it is the .223 chambers you have to be careful with). The best accuracy will most likely be found with hotter 5.56 ammo, but assuming similar quality ammo, the difference will be negligible.
Hi. I just bought my first AR. Bushmaster Carbon 15. The barrel is stamped .5.56 and the lower receiver is marked .223-5.56. In your opinion what would be the best round to fire through it? For safety more than accuracy. Just don’t want to ruin the weapon or have a malfunction that could injure someone. Thanks
peter3101 I just purchased a DPMS upper .223/5.56 and the instructions for breaking it in is to clean between every round for the first 10 rounds and then between every 10 rounds for several sets and then 25 rounds. Is this normal? I have never had a rifle or pistol that required that much effort in the initial firing.
The most important difference between .223 and 5.56 chambers is the length of the throat (or leade) for each chamber. I’ve heard that it is better to use 5.56 Nato in a .223/5.56 system, because of concentricity (keeping the chamber concentric). Grain effects the velocity the most, but lead distance might effect it ever so slightly (because of it being in the chamber length just slightly more (throat distance is more with better alignment). Better Ammo is important from what I heard also!
The most important difference between .223 and 5.56 chambers is the length of the throat (or leade) for each chamber. I’ve heard that it is better to use 5.56 Nato in a .223/5.56 system, because of concentricity (keeping the chamber concentric). Grain effects the velocity the most, but lead distance might effect it ever so slightly (because of it being in the chamber length just slightly more (throat distance is more with better alignment). Better Ammo is important from what I heard also!
Want to be even more confused? .223 Wylde (used by Rock River Arms and others) is in between these two chambers and can fire either round.
WilliamStauffer Technically the highest accuracy potential is .223 in a .223 chamber, however, most of us cannot do our part well enough to see the difference. Advantages of 5.56 is being able to shoot a bigger variety of ammo safely, and in theory 5.56 is more tolerant to fouling (because the chamber is cut a bit larger) and thus is more reliable. All these differences are very small.
FateofDestinee SavageHenry While manufacturers load to different specs, the only intrinsic differences between .223 and 5.56 ammo is the case wall thickness (a little thicker in 5.56), and the max pressure being a touch higher in 5.56, although most 5.56 ammo is not loaded to max. The bigger difference is in the chambers. .223 by spec (in the real world it varies between manufacturers) is a tighter chamber and shorter leade than 5.56 and as such the .223 will produce slightly higher pressures with the same ammo.
taino As the powder burns, the pressure increases, but as the volume increases (as the bullet travels down the barrel) the pressure decreases. If the bullet meets the high resistance of the rifling sooner (shorter leade), it will initially travel down the barrel slower. Since the powder is burning at a fixed rate, but the volume is increasing at a slower rate, this will cause higher pressure. For this reason, the shorter the lead and the tighter the chamber (5.56 chambers are generally a little more generous) the higher the pressure spike.
It is harder to explain then to understand. I hope that made sense.
Sometimes both, but if it say’s 5.56 then you can shoot both calibers. If it says 223 then you can only shoot 223.
peter3101
Does the barrel say 5.56 and .223 or just the higher 5.56?
I have a DPMS upper that is stamped 5.56 on the barrel. Will it handle a .223 round without any problem? Should it be stamped with both .223 & 5.56?
I read about 5.56 being a little heavier than .223 and yes the throat being also the difference! They also mentioned that running .223 in a 5.56 chamber can lead to concentric problems, because the .223 is smaller at the throat distance. The 5.56’s have thicker metal jackets and create more higher pressures from what I read. My take is that it probably is better to use a higher grain if you plan to use the .223 in a 5.56 chamber, to get it past the threshold faster in the beginning.
There are chambers that allow both .223 and 5.56 (Wylde chamber), but I am now figuring out that if it is chambered for 5.56, that your better off staying with the 5.56 and not using .223, unless your using a higher grain.
Just my take on how I believe things go!
I have a DPMS AR-15 that takes both .223 and 5.56 by design and yes the 5.56 is more accurate and more powerful, but I would not use 5.56 unless I knew for sure that it is chambered for such!
How the “leade distance” on a 5.56 AR will affect the velocity or energy on .223 round? is like a double jump not?
How the “leade distance” on a 5.56 AR will affect the velocity or energy on .223 round? is like a double jump not?
im not very familiar with the 223 is the 5.56 better for long distance or the 223
SavageHenry,
Can you check those listing numbers again? Maybe there were other details that accounted for the differences? For the same bullet weight higher velocity would make higher energy and lower velocity would make lower energy. I’m just going with physics here: energy = bullet weight x velocity squared. Maybe one did better over some distance ???