.223 VS 5.56 answered?

[RaisedByWolves]

Theres a lot of discussion on the net about the use of 5.56 in rifles Stamped as using .223 ammo by the manufacturer. This discussion came up again lately and I called around and got both some good and terrible answers, everything from "OK for semi autos but not Bolt actions" which as explained to me sounds reasonable, to "Their a totally different caliber" which is just out right false.


Not being totally satisfied, but feeling like I was getting somewhere with this issue I started searching the web and again found little of real use, until I stumbled upon this Direct from federal. Lots of pertinent info, but if you read the last bullet point and understand theres a lil CYA going on, I think we may have a tenitive answer, unless someone can come up with something concrete to the contrary.

• It is our understanding that commercially available AR15’s and M16’s – although some are stamped 223 Rem on the receiver – are manufactured with 5.56 chambers. Our advice however should be that it is the customer’s responsibility to know what their firearm is chambered for and choose their ammo accordingly.

http://le.atk.com/pdf/223VS556.pdf



And please, if were going to use wiki as any guide, I would like to see real world data that backs up the humongous pressure differences claimed measured out in FPS.


Im not claiming to have the final answer here, but Federals claim on this matter carries a lot more weight in my book than wiki.

[sjohn26]

http://www.razoreye.net/mirror/ammo-...cle_Mirror.htm


Q. What is the difference between 5.56×45mm and .223 Remington ammo?

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.

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.

[DaveIam]

so if i read this right, basicly, if its stamped 5.56 you can shoot both 5.56 and .223 rounds through it. but if its stamped .223 you should only shoot .223 rounds through it. right?

[mojo]

yep ... you got it.

[Plain Old Bill]

No flames, please....I'm going away for a few days, so ....in forty years of shooting these rounds, I have yet to run into any proof that a firearm has been damaged by mixing 5.56 NATO and .223 Remington. Not saying it has not happened, mind you- it may have and we may be unaware of it. Does anyone have knowledge of a firearm that has been damaged in this way, or even worse, a kaboom?
Not picking a fight, just curious.

[RaisedByWolves]

yep ... you got it.

Well, no he dosent.




I firmly believe based on the info given any modern made AR or its many Variants will be fine with 5.56. If you read through the info posted by myself and sjohn26, youll see its not cut and dried by any means, but most modern rifles should be fine.

Atleast this is how I read it.


I would ask again for a limited amount of speculation and as much fact as we can get on this topic.



.



.

[RaisedByWolves]

Heres some info I dug up from a link contained within the link sjohn26 posted. It not only gives info on different manufacturers chambers, but also what chambers they used when and in what models.


I think the information given in sjohns link on overpressure symptoms and signs of ammo/chamber incompatibility could be of use to those who dont have a definite answer to their rifles chamber or the ammo they may have.




http://groups.msn.com/TheMarylandAR1...pgmarket=en-us

http://groups.msn.com/TheMarylandAR1...tombrands.msnw

[CZ40P]

I read this web page years ago. It seems to explain it all to my satisfaction.

http://www.thegunzone.com/556v223.html

Buy a gun chambered for 5.56 and you are good to go.

[tom vito]

I read this web page years ago. It seems to explain it all to my satisfaction.

http://www.thegunzone.com/556v223.html

Buy a gun chambered for 5.56 and you are good to go.

Exactly.......

[DaveIam]

Well, no he dosent.
.

It sounds like I do. From everything I've been reading, thats the jest of it all.