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.

[Yo-Yo]

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

I'm not sure where you got that information, but you were misinformed.

Early Mini-14s were marked .223, but had 5.56mm NATO chambers and are safe to use with any 5.56 NATO factory round. It states this clearly in the instruction manual.

See the original manual for the first gen Mini-14 here:

https://ruger-docs.s3.amazonaws.com/_manuals/mini14-180.pdf

Ammunition:

The MINI-14 is designed to use either U.S. Minitary, Commercial Sporting, or other .223 (5.56mm) caliber ammunition manufactured to U.S. indurtry standards.

[Delta 21]

You mean I cant shoot a .308 in my 30-06?

[DEPcom]

Yes very poorly written. They should have started with buy the chambered in 5.56 then explain why. I have a Sig M400 Nato 5.56 chambered from Walmart Black Friday special. I think the special was 700 to 750.

Love that rifle...

[eastexsteve]

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

It's backwards from the 223/5.56 dilemma. .308 WIN has a tighter chamber dimension and higher pressure specs than a 7.62x51 NATO. Thus, more velocity. I have a Savage 110 Tactical rifle in .308 with a real tight chamber, and it won't chamber most 7.62x51 rounds. However, my HK91 in 7.62x51 NATO will shoot either.

[Lurker]

“I have a Garand. Got it for $125 from DCM before it became CMP.“

The CMP had a station at the last Zombie Shoot we did. Mrs L decided she wanted to give it a try. The nice folks running it chuckled a bit when she picked it up. “That’s a 30-06 there, ma’am.”

After a couple of minutes of instruction she proceeded to put 8 out of 10 on a man sized steel silhouette target.

That shut them up pretty quick.

She turned to me and said “I want one of these!”

So we are saving our pennies. They sure aren’t $125 these days.

L

[Yo-Yo]

You mean I cant shoot a .308 in my 30-06?

Yes, you can. You just need to install a firing pin extension.

They're available at Brownells for most rifle makes...

[Yo-Yo]

Please excuse the typos. I couldn't cut and paste from the .pdf manual, so I hastily typed it using notepad and neglected to use spell check before posting.

Ammunition:

The MINI-14 is designed to use either U.S. Military, Commercial Sporting, or other .223 (5.56mm) caliber ammunition manufactured to U.S. industry standards.

[Manly Warrior]

No, not a firing pin extension, but the US Navy converted 30/06 M1s to 762 NATO via a chamber insert. They did not work out so well. So the Navy rebarrelled with proper barrels then adopted the M14.

[onedoug]

Always preferred 7.62 myself.

[Blueflag]

FYI - my factory-fresh AR-10 would generate an ejection jam about 1 in 10 when I used .308, but ran like a sewing machine with 7.62. I tried several different gunsmiths who were puzzled, and fixed nothing.

THEN, I took it to a smith who retired from a career as a US Army armorer, and he had a 5 minute fix: he pointed out that when the rifle was made, a small amount of blue-ing gets into the chamber, which restricted, slightly, the chamber, just enough to screw up the .308 from ejecting regularly via the extractor. He lightly honed the chamber to remove the blu-ing, and then wiped it clean. We took it to the range and he and I then fired .308 rounds with impunity and consistency, and 7.62 without issue.

That was my experience.

[razzle9251]

I built my AR using a 223 Wylde chambering to avois this very issue.

[BuffaloJack]

“Early series mini 14’s should not fire 5.56”
What constitutes early series?
I bought my Mini-14 in 1983 and all I’ve ever shot with it is surplus 5.56 NATO.

[Yo-Yo]

“Early series mini 14’s should not fire 5.56”
What constitutes early series?
I bought my Mini-14 in 1983 and all I’ve ever shot with it is surplus 5.56 NATO.

Erroneous information. All Mini-14s chambered for .223 are also factory approved to use 5.56 NATO, with the exception of the Mini-14 Target, which should only use .223.

[Robert357]

In theory they are not interchangeable, but...........

Almost all modern AR type rifle platforms can chamber and fire both the .556 and the .223 Rem. Most ammo that you purchase from a store is .223 Rem. So the vast majority of the time there is not problem.

Where there is a problem is mostly for folks who have .223 Rem bolt action rifles or single shot Thompson Contender type pistols. If you have one of these and a buddy gives you some military surplus 5.56 ammo, then you “might” have a problem or might not depending on how strong the action is and how tight the chamber of your firearms is.

So is this a problem? It could be for a few, but not for most.

[sarge83]

What he said! 5.56mm rifle and you are good for .223 as well.

[gundog]

I think it only becomes a serious issue when people reload without trimming back the case length.

[Lurker]

“I think it only becomes a serious issue when people reload without trimming back the case length.”

Almost everything I reload gets trimmed to the recommended length. It’s not worth the risk. The only exceptions are .38 and .44 Spl. Everything I have that shoots those are chambered for magnums. So case length isn’t as critical. Although it can mess with crimping a bit.

L