.223 vs 5.56

[Chris_B]

I'm not so clear on why I'd feel I have to shoot .223 in a rifle chambered for 5.56

I think the point is, what's the way to definitively tell?

Example, I just bought a Colt. The lower has ".223" stamped on the lower

The barrel however reads "5.56 NATO". I am told that this rifle absolutely fires .223. No problems. But does it fire 5.56 safely?

From what I know, the answer is "yes". However I am a new owner and not conversant in all aspects of this rifle yet. I do not want to "know enough to be dangerous". I want to know

My understanding of my rifle is that it is now a 5.56 rifle. It was originally made as .223 but has been changed by the addition of a different upper and/or barrel. The modular nature of this rifle is such that from what I know, the barrels can be changed even if the upper is retained, thus changing the chambering. In this way, calibers from .223 to .458 can be used

But I am novice. Is what I posted above correct? I think it is, but I need to know I think that issue is what the thread revolves around- how do you know- really know- what the rifle is chambered for when you start swapping these parts. I am not new to firearms- I'd no sooner want to put a 7.62 into my M1 than I'd want to put the wrong round into my AR15

 

[Marquezj16]

@Chris B - the better safe approach for the OP would be to shoot .223 because he does not know what his barrel is chambered for. Until he gets a definite answer 5.56 or .223, then just shoot .223 on it. If he finds out that it's a 5.56, then he can shoot both. In no way am I saying only shoot .223 if you have a 5.56.

 

[wwd88888]

.223 bolt

I notice that all these "warnings" invariably include "AR".

I've never considered a .223 bolt gun simply because .223 is a no-no for hunting deer where I live. My guess that that a bolt gun will be a pure .223 and will have much tighter chamber tolerances than an AR. I'd only shoot commercial .223 in a bolt gun.

 

[4runnerman]

I know 2 people that have been shooting military loads in their run of the mill 223's for years.1000's of rounds ,no issues at all. It's a hype started by some one years ago.

 

[Marco Califo]

One reference on the subject would be Nosler's #6 reloading manual because they list loads and descriptions of both .223 and 5.56.

Really? This Nosler? Looks to me like they also think they are the same. They list the exact same loads exactly once with "223 Remington & 5.56x45 NATO - 69 Grain" as the heading.

http://www.nosler.com/Reloading-Data/223-Remington--5.56x45-NATO-69-Grains.aspx

Same is true at AmmoMan.com:

http://www.ammoman.com/index.htm

Hmmm.

 

[20thru45]

Marco,

The printed book varies from the online and .223 loads are listed up to 60 grn and 5.56 start at 69. Thanks for the link.

 

[Clark]

Here is a pic where I have overloaded an AR14, and the shape of the extractor and the ejector are imprinted on the case head.

Here are some more 223 case heads where the pressure if even higher.

While exploiting the huge amount of safety margin in the .223 cartridge, I have got 4200 fps more than once. I have got 4100 fps with long case life.

What does it all mean?
These three pieces of brass that look bad are at way higher pressure than the 4100 fps brass, that looks normal.