For those members NEW to AR's...

[Werewolf]

Many otherwise knowledgeable firearm enthusiasts quite often do not know the differences between Rem .223 and NATO 5.56 ammunition and the chambers that they are designed to fit in and that worse case it can be dangerous to shoot 5.56 NATO out of a spec .223 chamber.

Since there is a push to bring in new members and they are especially prone to the misconception that the .223 and 5.56 NATO calibers are interchangeable I thought it would be appropriate to post the facts about why they are not interchangeable. Below is a link to a very well written article that explains the differences between the two chambers, the differences between the two cartridges and why it can be dangerous to shoot 5.56 NATO out of a .223 Rem chamber.

Though I encourage those new to AR's to read the entire article a quick summary of the issue boils down to:

The significant difference between the .223 Rem and 5.56 NATO lies in the rifles, rather than the cartridges themselves. Both the .223 and 5.56 rounds will chamber in rifles designed for either cartridge, but the critical component, leade, will be different in each rifle.
The leade is the area of the barrel in front of the chamber prior to where the rifling begins. This is where the loaded bullet is located when a cartridge is chambered. The leade is frequently called the “throat.”
On a .223 Remington spec rifle, the leade will be 0.085”. This is the standard described by the Sporting Arms and Ammunition Manufacturers’ Institute, Inc. (SAAMI). The leade in a 5.56 NATO spec rifle is 0.162”, or almost double the leade of the .223 rifle.
A shorter leade in a SAAMI spec rifle creates a situation where the bullet in a 5.56 NATO round, when chambered, can contact the rifling prior to being fired. By having contact with the rifling prematurely (at the moment of firing), chamber pressure can be dramatically increased, creating the danger of a ruptured case or other cartridge/gun failure.

SAAMI's interchangeability table states that you can shoot .223 out of a 5.56 NATO chamber but not vice versa.

There's more to it than that but leade is the main issue.

Here's the link to the article from the Guns and Patriots section of the Human Events web site: [h=1].223 Remington vs. 5.56 NATO: What You Don’t Know Could Hurt You[/h]

For those new to AR's what this all means is you can shoot .223 Rem cartridges out of both a .223 spec chamber and a 5.56 NATO chamber without issue but you should not shoot 5.56 NATO out of a .223 spec chamber.

 

[beast1989]

I don't own any rifles but this issue is one that leads to my hesitancy. Once i get into ARs im choosing one caliber and sticking to it for the sake of simplicity. I know the differences but I wonder what caliber you guys prefer out of the two.

 

[twotonevert]

Thank you for posting the link and the information. I did extensive research before I purchased my rifle and sought advice from a few friends. This is the reason I made sure I purchased a rifle chambered in 5.56 so I could shoot either cartridge. It was confusing until I read this article.

Sent from my Ford F-150 using Forum Runner

 

[twoguns?]

Thank you for posting the link and the information. I did extensive research before I purchased my rifle and sought advice from a few friends. This is the reason I made sure I purchased a rifle chambered in 5.56 so I could shoot either cartridge. It was confusing until I read this article.

Sent from my Ford F-150 using Forum Runner

You can also look for Wylde chambered rifles

.Good read, hope I didnt confuse anyone

 

[John Zane]

I would like to add to this by saying a P-mag full of 223 is not worth $80

 

[Coded-Dude]

Are the differences between .223 spec chamber and a 5.56 NATO the same as the differences between .308 spec chamber and 7.62 NATO? Or do they have their own list of variances and nuances....?

 

[Stephen Cue]

Good post, thanks for sharing & caring Werewolf!

 

[OKC_Jim]

I don't own any rifles but this issue is one that leads to my hesitancy. Once i get into ARs im choosing one caliber and sticking to it for the sake of simplicity. I know the differences but I wonder what caliber you guys prefer out of the two.

I prefer 5.56 over .223. With a 5.56 barrel you can fire both 5.56 and .223. You are not supposed to fire 5.56 in a 223 barrel. Also note that there are some differing chambers, such as the already mentioned Wilde Chamber, which also allows for both .223 and 5.56.

Hope that helps,

Jim

P.S. I edited this after Werewolf pointed out that I accidentally got something backwards. I'm not trying to hide my error. I fixed my mistake to keep anybody else from reading it and getting it wrong.

 

[BIG_MIKE2005]

I prefer 5.56 over .223. With a 5.56 barrel you can fire both 5.56 and .223. You are not supposed to fire .223 in a 5.56 barrel. Also note that there are some differing chambers, such as the already mentioned Wilde Chamber, which also allows for both .223 and 5.56.

Hope that helps,

Jim

So if your not supposed to shoot a .223 through a 5.56 barrel, why are the producing them in such a manner? I was also reading up on this when I started looking into getting an AR finally a couple months ago. I had read the info about shooting a 5.56 out of a .223 chamber but did not see negative info about shooting .223 out of a 5.56 barrel.

 

[Werewolf]

I prefer 5.56 over .223. With a 5.56 barrel you can fire both 5.56 and .223. You are not supposed to fire .223 in a 5.56 barrel. Also note that there are some differing chambers, such as the already mentioned Wilde Chamber, which also allows for both .223 and 5.56.

Hope that helps,

Jim

You got that backwards. You can shoot .223 out of either chamber. You shouldn't shoot 5.56 out of a .223 chamber.

The Wylde chamber was designed to shoot both. At least one AR maker had/has a wylde chamber option though I don't remember which one.

Personally I'd go with the 5.56 chamber as it is designed, among other things to handle much higher pressures than .223. IIRC (someone may want to look this up) .223 ammo is spec'd at max PSI of around 52K while 5.56 ammo is spec'd out at around 59 to 61K which means the 5.56 chamber has to be built to handle higher pressures than the .223 chamber. Plus with the longer leade of the 5.56 chamber shooting .223 commercial ammo out of the 5.56 chamber as is noted in the article and by SAAMI is not an issue.

Long story short don't shoot mi-surp 5.56 out of your .223 bolt action varmint rifle.

Here's a link to the SAAMI publications page. Lots of good info there: http://www.saami.org/specifications_and_information/index.cfm