.223 Cal vs. 5.56 NATO?

[The Sensei]

Can someone help me here?

I am in the market for an AR15 or M4 to use in 3-gun competition. In researching the different makes etc. I noticed a reference to .223 caliber being different than 5.56 NATO. I thought they were the same. If I have a .233 rifle can I use 5.56 NATO and vice versa?

As I have an Armalite AR-15 with 20" barrel/ A2 top...one of my options is to pick up a 16" flattop upper assembly to use on the Armalite. But I want to stay consistent with my current gun and .223 ammo supply. Does it matter whether it is 5.56 NATO or .223 cal?

Thanks in advance for any insight on this.

 

[Redlg155]

Here's what these folks have to say.

Armalite.

http://www.armalite.com/library/techNotes/tnote45.htm

Fulton Armory.

http://www.fulton-armory.com/556-vs-223-Chambers.htm

AR15.com folks.

http://www.ammo-oracle.com/#diff

If you are going to use your rifle in 3 gun competition where ultra reliability is definitely an issue then I'd definitely get a chrome lined barrel with a 5.56 chamber. You can get those from several manufacturers. Personally I like the Bushmaster.

Good Shooting
Red

 

[The Sensei]

Red
Much obliged! This is exactly the info I was looking for.
Thanks!!

 

[Zak Smith]

Sensei,

Brian Enos' forums (link) are the best source of 3Gun information I've found so far. Some of the top 3Gun shooters post there, and you'll get some good advice about what you probably want in a 3Gun AR.

Some things to consider:

1. Power factor. If the matches you want to shoot require .223 to meet "Minor" power factor (160PF for rifle), then you'll have to double-check 55gr ammo makes Minor in a 16" barrel. To get around this problem, and hit steel a little harder, I shoot 68gr out of my 16" AR. An 18" barrel might be a better choice.

2. Twist. Along with the first point, if you want to shoot the heavy 75-77gr loads (for PF, cross-wind margin), then strongly consider a 1:8" or 1:7" twist barrel.

3. Gas system length. The short gas system standard on most 16" AR's impart significantly more force to the bolt carrier and thus the rifle will move more. Consider a full-length gas system, or mid-length if you have to get a 16".

4. Comp. Really consider having a good muzzle compensator installed. It makes a big difference for retaining sight picture while shooting fast. The JP "BC Comp", Benny Hill's comp, and the Miculek comp are all good.

There are other chamber choices than 223 or 5.56. There's also the "Wilde" chamber which is somewhere in-between.

Here's a picture of my 3Gun AR-15:

-z

 

[NevadaPistolero]

The RRA AR15 has the "Wylde" chamber, you can shoot either .223 or 5.56 with no problems.

 

[bvmjethead]

Get a rifle chambered for 5.56 because you can fire 5.56 and .223 in it.

You cannot fire 5.56 in a rifle chambered for .223, or I should say you should not.

 

[Dr.Rob]

5.56 Nato and .223 are the SAME.

The chamber dimensions on each rifle may be slightly different, but that is NOT the same as saying the rifles are not the same caliber.

A rifle that allows a little more head space or flex room for a swollen cartridge, is still going to fire 223/5.56 ammunition.

I'm not advocting shooting tracer ammo in your bolt gun, but you can.

There is NO mfg. that currently states the rounds are different. There is NO difference in SAAMI spec between the two designations.

You are simply stating one rifle has a "sloppier" (or overesized) chamber, this will NOT increase the accuracy of your rifle, rather its designed to keep firing when its dirty.

 

[Absolut]

Get a rifle chambered for 5.56 because you can fire 5.56 and .223 in it. You cannot fire 5.56 in a rifle chambered for .223, or I should say you should not

this man is correct

 

[NevadaPistolero]

I would suggest you read this info before firing 5.56 in a gun marked .223....... Click Here

 

[The Sensei]

THANKS GUYS for the good info. This has been very helpful.

 

[AR-15Nutt]

"""Get a rifle chambered for 5.56 because you can fire 5.56 and .223 in it. You cannot fire 5.56 in a rifle chambered for .223, or I should say you should not"""""


so......., how does one know what their rifle is chambered for when on the ID side of the rifle it reads ".223 Rem." then looking at the barrel, it reads "5.56 NATO"

i do not believe there is a lower receiver marked "5.56 NATO." ..., but every barrel i've seen is marked "5.56 NATO.

there is some confusion as to what designation to stamp in a rifle/carbine, both designations show up on one gun.........

 

[meathammer]

i do not believe there is a lower receiver marked "5.56 NATO."

My 16" Armalite (M15A4 carbine) is marked 5.56mm on the lower receiver.

 

[bvmjethead]

The lower has nothing to do with the chambering of the cartridge.

I suggest going to www.ar15.com and checking out the tacked threads and the Ammo Oracle.

Very good reading by people with far more intelligence than I'll ever have.

 

[sasnofear]

AR-15Nutt- seems to have the same idea as me, i dont know about .223 however i do do know the 7.62mm rifle will handle .308 easy whereas a marked .308 rifle may have sticky extraction when using the 7.62 NATO stuff. of course their the same caliber etc but i think- dont quote me- but i think the nato has minutely larger case dimensions- thicker brass or something.

hope this helps.

 

[ny32182]

There is NO mfg. that currently states the rounds are different. There is NO difference in SAAMI spec between the two designations.

I believe that the NATO spec calls for higher pressures than the civilian .223 spec. Further, I think the cartridge dimensions are slightly different, but couldn't tell you exactly how. The NATO chamber allows a bit more headspace.

Every colt and bushmaster lower I've seen has been marked for both, but its the upper that is really the determining factor. If your barrel says "5.56mm NATO" on it, then that is what it is chambered for, but you should be able to shoot both without a problem.

As has been said, its not advisable to fire 5.56 in a .223 chamber.

 

[Kentucky Rifle]

I thought both calibers were the same. I really did. However, I just went to my safe and looked at the barrel markings on my Bushmaster Shorty. It says, "5.56 NATO".

KR

 

[org]

The cartridge dimensions are the same. The difference is in the throat area of the chamber AFAIK. The 5.56 has a bit more length before the rifling starts, allowing a little hotter loading.