Using 5.56 NATO in .223 Rem B/A

[quatin]

Hi,

Before I ask what must be a common and newbie question. I have to say I'm not going to attempt to do this, I was just curious.

I've read people warning others about not using 5.56 NATO in .223 rem semi-autos. But what about single shot rifles? Can you just hand fit a 5.56 nato round into the throat and shoot it? I heard that there's higher pressure in a 5.56 nato round, but it's not like shooting a .308 in a .223 rated barrel and "just logically thinking" shouldn't the tolerances of a gun barrel be able to handle a bit hotter load without heavy damage, but just faster wear?

 

[TexasRifleman]

Start with the Ammo Oracle. More than everything you wanted to know.

You will get a variety of opinions. The gist of it is:

Military M16s have slightly more headspace and have a longer throat area, compared to the SAAMI .223 chamber spec, which was originally designed for bolt-action rifles. Commercial SAAMI-specification .223 chambers have a much shorter throat or leade and less freebore than the military chamber. Shooting 5.56 Mil-Spec ammo in a SAAMI-specification chamber can increase pressure dramatically, up to an additional 15,000 psi or more.

Here is SAMMI's take on it, a more conservative approach as you'd expect:

The .223 Remington is rated for a maximum of 50,000 CUP while the 5.56mm is rated for 60,000 CUP. That extra 10,000 CUP is likely sufficient to cause a failure in a chamber that's only rated for the "sporting" .223 Remington.

So your answer will probably depend more on WHAT rifle you want to use specifically. Older rifles it might be a problem, a new rifle maybe it won't. Don't you love it when it's not a simple yes no answer?

 

[Metapotent]

The funny thing is though, there are some rifles that are labled '.223 Rem' or '.223' but they are still made to handle the extra pressure of a 5.56 NATO round.

But I must admit that I had no idea of the difference between the 5.56 and the .223 at one point.

In fact, I had chambered and fired around 150 British SS109 5.56 through my old Bolt-action Savage in .223. Nothing went wrong, the gun didn't blow up, and the cases didn't get stuck and the gun was shooting fine. But when the rangemaster came and saw what I was doing he freaked out and offered to check my gun for damage then he explained to me "Don't EVER, never, ever, never, ever fire 5.56 rounds in a .223 rifle!"

 

[ScottsGT]

RRA uses the "Wylde" chamber, which is good for .223 or NATO 5.56
But all the arguments I see on this state that the 5.56 NATO round has higher pressures, but when you start comparing .308 to the NATO 7.62, everyone states that commercial ammo has higher pressures. [scratch head smilie here]

 

[quatin]

So the obvious question leading up now is how do you tell if your gun can shoot 5.56 NATO? For argument's sake I have that brand new Savage 12 series in .223.

 

[taliv]

call savage and ask them?
read any markings on your barrel?

 

[hps1]

Received this explanation from Bushmaster today in response to my question as to the chambers in their Predator and CMP AR's:

Subject: Chambers, DCM/CMP & 24" Fluted Varminter

The DCM/CMP & 24" Fluted Varminter barrels have a custom match hybrid chambering that uses the tighter SAAMI Spec headspace from the shoulder of the chamber to the bolt face. It has the longer "Leade" or throat that will accommodate the 5.56mm ammunition so it can be used without developing higher pressures as in a .223 caliber chamber that have a shorter "Leade" or throat.

Both 5.56mm and .223 caliber ammunition can safely be used in the DCM/CMP & 24" Fluted Varminter rifles.

Regards,
hps

 

[Don't Tread On Me]

Here is a PDF that explains it all.


http://www.ar15barrels.com/data/223vs556.pdf