.223 vs 5.56 mm

[drowe44]

I was at a local gun store yesterday and heard the salesman tell a customer that they needed to be careful about the AR they bought. If it is chambered for .223 it won't safely shoot 5.56 mm because of the higher chamber pressure. Now I have been shooting and reloading for more than 25 years and I've never heard that before. However I want to keep an open mind. Does anyone know if there are rifles being built to accept different chamber pressures?

[DOC]

Nope. Never had a problem. But I do shoot .223 more often.

[Deano]

IF it's chambered for .223 the 5.56 round can cause big problems, but .223 in a 5.56 chamber is ok.Never seen a .223 AR though myself.Most think they are the exact same round but they aren't.Thats also where the .223 wylde chamber comes in, a happy medium so to speak.Basically a 5.56 chamber has larger dimensions(throat) than a .223 chamber thus making 5.56 rounds make more pressure in a .223 chamber.
A little info http://en.wikipedia.org/wiki/.223_Remington
Hope this helps
Ster

[DOGSHOOTER]

Rifles Chambered For 223 Have A Shorter Throat Than 5.56 Chambers. Some 5.56 Rounds Have Longer Bullets Or Are Seated Out Further. When Fired In A 223 Chamber,this Can Greatly Increase Chamber Pressures. 308 Vs 7.62 Chambers Have The Same Concern. It Has Nothing To Do With 1 Chamber Withstanding Higher Pressures.

[CO-FreeShooter]

The main thing you need to look at is if it says chambered with ".223rem" or .223 cal. You can fire 5.56mm through a .223 cal barrel. But you cannot fire a 5.56mm round through a .223 rem barrel. But i actually have never seen a .223 rem only barrel. I hope this helps out. I had a friend ask me because i had bought a case of 5.56 and he has a mini-14 chambered .223 cal not .223 rem so its legit.

[Deano]

The main thing you need to look at is if it says chambered with ".223rem" or .223 cal. You can fire 5.56mm through a .223 cal barrel. But you cannot fire a 5.56mm round through a .223 rem barrel. But i actually have never seen a .223 rem only barrel. I hope this helps out. I had a friend ask me because i had bought a case of 5.56 and he has a mini-14 chambered .223 cal not .223 rem so its legit.

This makes no sense...and I've never heard of a .223 cal rifle either..223 rem yes but....??.Please explain, some sources would help too.
Ster

[Colorado Osprey]

Most of you will know where this came from without the link (They are different):


In the 1950's, the US military adopted the metric system of measurement and uses metric measurements to describe ammo. However, the US commercial ammo market typically used the English "caliber" measurements when describing ammo. "Caliber" is a shorthand way of saying "hundredths (or thousandths) of an inch." For example, a fifty caliber projectile is approximately fifty one-hundredths (.50) of an inch and a 357 caliber projectile is approximately three-hundred and fifty-seven thousandths (.357) of an inch. Dimensionally, 5.56 and .223 ammo are identical, though military 5.56 ammo is typically loaded to higher pressures and velocities than commercial ammo and may, in guns with extremely tight "match" .223 chambers, be unsafe to fire.

The chambers for .223 and 5.56 weapons are not the same either. Though the AR15 design provides an extremely strong action, high pressure signs on the brass and primers, extraction failures and cycling problems may be seen when firing hot 5.56 ammo in .223-chambered rifles. Military M16s and AR15s from Colt, Bushmaster, FN, DPMS, and some others, have the M16-spec chamber and should have no trouble firing hot 5.56 ammunition.

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.

The military chamber is often referred to as a "5.56 NATO" chamber, as that is what is usually stamped on military barrels. Some commercial AR manufacturers use the tighter ".223" (i.e., SAAMI-spec and often labeled ".223" or ".223 Remington") chamber, which provides for increased accuracy but, in self-loading rifles, less cycling reliability, especially with hot-loaded military ammo. A few AR manufacturers use an in-between chamber spec, such as the Wylde chamber. Many mis-mark their barrels too, which further complicates things. You can generally tell what sort of chamber you are dealing with by the markings, if any, on the barrel, but always check with the manufacturer to be sure.

Typical Colt Mil-Spec-type markings: C MP 5.56 NATO 1/7

Typical Bushmaster markings: B MP 5.56 NATO 1/9 HBAR

DPMS marks their barrels ".223", though they actually have 5.56 chambers.

Olympic Arms marks their barrels with "556", with some additionally marked "SS" or "SUM." This marking is used on all barrels, even older barrels that used .223 chambers and current target models that also use .223 chambers. Non-target barrels made since 2001 should have 5.56 chambers.
(EDIT: OLYMPIC Target models will have a 223 chamber with the SUM barrel and/or either chamber in the SS barrel)

Armalite typically doesn't mark their barrels. A2 and A4 models had .223 chambers until mid-2001, and have used 5.56 chambers since. The (t) models use .223 match chambers.

Rock River Arms uses the Wylde chamber specs on most rifles, and does not mark their barrels.

Most other AR manufacturers' barrels are unmarked, and chamber dimensions are unknown.


Opinion: In general it is a bad idea to attempt to fire 5.56 rounds (e.g., M193, M855) in .223 chambers, particularly with older rifles.


.223 Remington chambers will give you slightly better accuracy, which is important for a match or varmint rifle. Any loss of feeding and cycling reliability and the restriction against shooting military ammo isn't as important as the accuracy gains for a rifle used in these roles, because for these rifles, accuracy is everything. People who just want to plink or who plan to shoot military ammo (such as most of the cheap surplus ammo available), and especially those who may use their AR as a weapon, should choose 5.56 chambers.

[CO-FreeShooter]

This makes no sense...and I've never heard of a .223 cal rifle either..223 rem yes but....??.Please explain, some sources would help too.
Ster

http://en.wikipedia.org/wiki/5.56x45mm_NATO
There should be enough proof for you. Just read it and you will see that it makes sense. SAR

[Deano]

http://en.wikipedia.org/wiki/5.56x45mm_NATO
There should be enough proof for you. Just read it and you will see that it makes sense. SAR

Actually after reading this it only reiterates my original post.NO where does it say anything about a .223 cal marked rifle (which I still havent seen)having a chamber different from a .223 REM chamber..223 is .223 is .223....still not considered good to shoot 5.56 spec ammo through a rifle marked .223.
Somehow I think your a bit crossed up in your chamberings, any .223 rifle is designed to shoot .223 REMINGTON ammo, 5.56 is loaded to higher presssures as well as having different chamber dimentions....period.
So no it still doesn't make sense.Sorry.
BTW Colorado Ospreys' post actually makes you make more sense, but given the info there it still sounds hit or miss as to whether or not a particular make of rifle will safely shoot 5.56 nato ammo...
Ster

[CO-FreeShooter]

Actually after reading this it only reiterates my original post.NO where does it say anything about a .223 cal marked rifle (which I still havent seen)having a chamber different from a .223 REM chamber..223 is .223 is .223....still not considered good to shoot 5.56 spec ammo through a rifle marked .223.
Somehow I think your a bit crossed up in your chamberings, any .223 rifle is designed to shoot .223 REMINGTON ammo, 5.56 is loaded to higher presssures as well as having different chamber dimentions....period.
So no it still doesn't make sense.Sorry.
BTW Colorado Ospreys' post actually makes you make more sense, but given the info there it still sounds hit or miss as to whether or not a particular make of rifle will safely shoot 5.56 nato ammo...
Ster

I'm not going to argue with you. If you have some point to make you have made it. All I am saying is that I have talked to multiple people on this, and my friend has a mini-14 that says .223 "cal" on it. Not "rem". So take it how you want. And he has fired the 5.56 ammo through it and he has had not problem. But your probably right though. You win.