5.56 NATO vs .223 Rem

Am Shooting Journal ^ | 4/9/2019 | M Collins

[w1n1]

There's already a wealth of information out there, both online and in print, about the differences between .223 Remington and 5.56x45mm NATO. Sadly, a lot of this information is either misguided, ill-founded, or just plain wrong.
We’re going to try to set the record straight. These are two cartridges that are really just about as similar as you can get, and are identical from an 5.56 NATO VS. .223 Remington external viewpoint, so the confusion is understandable. Hopefully, though, we can clear up some of the issues surrounding these two cartridges and help you choose between them.
This is especially important as these are the two most popular AR-15 calibers, so many shooters looking to buy an AR might be wondering which chambering is better than the other. And we’ll get into that too. Think of this as more of a chambering vs. chambering discussion, rather than a caliber vs. caliber one, although we’re going to take a look at things like ammo availability and performance as well.

HISTORY In the years following the Korean War, work began in the U.S. on a rifle and cartridge that could compete with the German STG-44 and the Russian AK-47, both relatively light (for the time) rifles firing an intermediate caliber that was controllable under fully automatic fire.
The goal was to create a round that was high velocity, relatively light so that troops could carry hundreds of rounds without issue, but with enough power to still be effective against battlefield targets at 500 yards.
The U.S. military also wanted a new lightweight combat rifle to fire the new round. In early 1957, the following standards for the round and accompanying rifle were set:
• A .22-caliber bullet that remained supersonic past 500 yards
• Rifle weight of 6 pounds or less
• Magazine capacity of 20-plus rounds
• Select fire for both semiautomatic and fully automatic use, while remaining controllable at full-auto
• Penetration of a U.S. WWII-issued steel helmet on one side at 500 yards
• Penetration of .135-inch steel plate at 500 yards
• Accuracy and ballistics equal or superior to M2 ball ammunition (fired by the .30-06 M1 Garand)
• And wounding ability equal or superior to the M1 carbine firing .30-caliber carbine ammunition

As part of the development of this new rifle and new round, Eugene Stoner, designer of the AR-10, was asked to attempt to scale down his AR-10 design to the specifications required, and to work on developing a round for it to fire. Read the rest of 556 vs 223.

[beebuster2000]

interesting. i aways thought they were interchangeable. i guess not.

ruger mini14 i thought could fire the nato round, but apparently one should not.

[Lurker]

This article is so poorly written as to be nearly incomprehensible

Here’s all the average Joe or Jill needs to know. Buy your AR chambered in 5.56 mm NATO. Then you don’t have to worry about it as you can safely fire either one.

L

[real saxophonist]

This article is so poorly written as to be nearly incomprehensible

In other words, about average for 'Am Shooting Journal'.

[junta]

I put a few rounds of .556 Wolf 55gr thru a Ruger varminter in .223 and had sticky bolt lift. So while not a true firearms expert I would not put a .556 load in a .223 chambered firearm.

I have a Rock River Arms varminter rifle length upper with the .223 Wylde chamber and I am happy as a pig in slop with its accuracy with all loads.

[Yo-Yo]

ruger mini14 i thought could fire the nato round, but apparently one should not.

Ruger Mini-14s are chambered in 5.56mm NATO, so can shoot either 5.56 or .223.

\https://ruger.com/products/mini14RanchRifle/models.html

[rjsimmon]

Buy your AR chambered in 5.56 mm NATO. Then you don’t have to worry about it as you can safely fire either one.

Simple, concise, and quite accurate. The difference b/w the two comes down to throat length and the NATO chambered weapon is far more accommodating to the .223 then the obverse.

[Vaquero]

Great varmint rounds.

I agree with the carry-ability of the aluminum/plastic/steel ARs and light ammo. Plus wounding ties up more grunts than killing.

That being said I personally, in a tight situation, would rather have an M14 (or equivalent) with the hard hitting and penetration of the 7.62X51. but that’s just me.

[Celtic Conservative]

Early production mini 14’s are .223 only. Later production mini 14’s (serial # starting with a “5” or higher will shoot both.

CC

[mad_as_he$$]

Geez, not this Shit again.

https://www.youtube.com/watch?v=VCS4fXFmCyA

[Celtic Conservative]

Please see my post # 9. Early series mini 14’s should not fire 5.56.

CC

[lgjhn23]

FWIW, I make 300 AAC Blackout from 5.56 military brass rather than .223 for my AR pistol. I’ve found, as many others have, that most of the military 5.56 brass to be just a tad thicker which makes for a good neck thickness for resulting 300 BO cartridges. Of course, the military brass has the primer crimp to deal with but a Dillon swaging tool makes quick work of that.
IF I were to switch uppers for the more standard calibers, like others have posted above, it would be for the 5.56 NATO rather than .223.

[Lurker]

“That being said I personally, in a tight situation, would rather have an M14 (or equivalent) with the hard hitting and penetration of the 7.62X51. but that’s just me.”

I had an wonderful National Match M1A until recently. The serial number was under 24,000 and all TRW parts. It had the correct Springfield Rangefinding scope on it, a Gen II. I got it 20 years or ago so from a guy going through a divorce. I paid around $400 dollars for it. It had a beautiful tiger birch stock hand rubbed with 15 coats of tung oil and was professionally glass bedded. Just gorgeous.

I had 10 SA factory magazines for it. It’s a no **** 800 yard rifle.

I sold it recently and got nearly $3,000 for the package. Why?. I spent a day humping it in the field, that’s why. Damn near killed me. Between the rifle, magazines, and ammunition it was over 20 pounds. I’m just plain too old for that.

Now my .308 is a Savage bolt gun. It’s wicked accurate out to 500 yards or so and weighs less than half. The M1A is a fine rifle for a younger man than I.

L

[wastoute]

When it comes to shooting I prefer the M1A. When it comes to carrying it all day I prefer the AR.

[Blueflag]

Exactly. Same for an AR-10. Get one chambered for both 308 Win and 7.62 mil

[Lurker]

“Same for an AR-10. Get one chambered for both 308 Win and 7.62 mil”

Hard to do that as there are small but significant differences between the two. Heavier .308 loads generate more pressure than the standard 7.62 NATO loading. Trying to push a 180 grain bullet could present problems in a 7.62 chamber. It’s not likely but it is possible.

It’s a lot of hair splitting, I know. But when a small explosion is going off inches from your face it’s best to err on the side of caution.

L

[Manly Warrior]

The graphics should help many understand the issues. A longer/looser throat/leade results in a softer start-
However, the issue remains, NATO is loaded to about 5000PSI more than SAAMI 223. So, a 55 grain 556 NATO round in a 223 Rem chamber produces as high as 77k psi, (SAAMI method) while the SAAMI chamber/round generates 50k CUP/55K psi.

Adding more confusion to the issue is the 4 yes, four different methods used to determine pressure- CIP ( European standard- 63500 PSI) NATO ( kind of hybrid 63000 psi) SAAMI (50k CUP/55k PSI)and US Army SCATP (55k PSI).

Interestingly, the hybrid chamber (223 Wylde in particular) make the best of both chambers- generous chamber body dimensions, tight throat, longer freebore and shallow leade angle generally produce better results with either loading and allow interchangeability with no risk of excessive pressure spikes.

The wide throat (.226” of the 556 NATO chamber allows for more reliable chambering when dirty, but also contributes to less innate accuracy than the 224 diameter freebore diameter of the 223 Rem and most hybrids, with almost no clearance, bullets are much more closely aligned with the leade into the rifle which contributes to better accuracy.

What chambers do the Warrior household AR15s wear? The NM Service rifles- 223 Wydle or 223 AMU ( for the 1/6.5-90 grain bullet 1000yard gun), the Varmint bolt gun- 223 Rem with 1.5 deg leade, the Carbines behind the doors? 556 and NATO Spec ammunition.

[Blueflag]

My Bushmaster AR-10 (not a pricey rifle) does just fine with both - built for it from the factory ;-)

[Vaquero]

I have a Garand. Got it for $125 from DCM before it became CMP. Two of my boys have Garands. One is a National Match I picked up from a friend’s, friend’s widow for my son for $800. Extremely accurate. We hump them with our cars to the range. I wouldn’t carry it in the field…not at my age. When I do hunt it’s my Marlin 336 in .35 Remington. Nice, fairly light short easy to swing. Enough power and range here in the NE.

If World chaos happens I’d probably hump my M1 carbine. Low power but enough for close range work and only 5 lbs.

[Lurker]

“If World chaos happens I’d probably hump my M1 carbine. Low power but enough for close range work and only 5 lbs.”

Not a bad choice. Fun little guns, too. My brother had one, an Inland if I remember right. But the idiot sold it when he got in a jam. I told him I’d take it off his hands if he ever needed to but, like I said, he’s an idiot.

Loaded with soft points it’d do the job under all but the most extreme circumstances.

Good luck to you.

L