can my ar 15 shoot 5.56?

223 and 5.56 are completely interchangeable.

Except someone is going to cite a tome how they are not.

I recommend calling Rock River and asking their customer service.

Chances are that it's just fine. I'm not going to write a tome about anything, but make sure it's a 5.56 barrel before shooting a bunch of actual 5.56.

If the barrel is marked .223 they are not interchangeable. 556 is loaded to higher pressures and has a slightly different chamber. In your AR your fine but in older rifles use caution.

Certaindeaf said:

Except someone is going to cite a tome how they are not.

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You mean like hornady, Lyman, lee, Sierra, etc...?
Maybe not a tome, but definitely disclaimers in their data.

Bushmaster will tell you that you can shoot .223 in a 5.56 barrel but, due to higher NATO pressures, no 5.56 in a .223 barrel. Google .223 vs 5.56 and you'll find plenty of articles on this subject.

Many of the Bushmasters we had at work would pop primers when we shot M193 for one qual course.

pretty sure most RRA barrels are setup to run 5.56. If it was a litigious problem i suspect the industry would have created better safeguards like .38 special vs .357 magnum.

a vast majority of AR uppers are cut with 5.56 chambers and not .223 chambers. .223 chambers exist, but typically on varmint/target specific uppers and even then are usually a special option. As for 5.56 in a .223, I saw an article on here not too long ago where several (6 i think) rifles were tested. In the 2 .223 bolt guns when used with 5.56 ammo pressures in excess of proof loads were achieved. They did not blow up, but I have plenty of .223 laying around to feed to my .223 chambers that I am not going to risk it.

Make sure it's not a Wilde cut chamber.

Lot of FAIL in this thread.

READ.

http://www.ar15.com/ammo/project/AmmoOracle_061808.pdf

Important part.

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.

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The Wylde chamber is safe for both types
That's its purpose in life--accuracy coupled with safety. If your gun has a Wylde chamber, you are gtg.

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Concur.

You could be the next Darwin Award recipient if you shoot 5.56 in a 223 chambered rifle.

thanks all and Taliv

a side note is that many of the cheaper ARs (which often have 223 chambers or worse, tight 556 chambers) seem to be sort of optimized for the weaker wallyworld ammo and tend to cycle better with it.

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Good point.

I'm pretty sure that all RRAs that aren't chambered in 5.56 are chambered in .223 Wylde, which, as MOST of us realize, is safe for both .223 and 5.56.

The Rock River Arms (RRA) catalog specifies two chambering configurations/options for their AR-15 rifles: "5.56mm NATO Chamber for 5.56mm & .223 Cal." and ".223 Wylde Chamber for 5.56mm & .223 Cal." To the question of "What is a Wylde Chamber?", RRA responds "The Wylde chamber was designed as a match chambering for semi-automatic rifles. It will accomodate both .223 Rem and 5.56 NATO ammunition. It is relieved in the case body to aid in extraction and features a shorter throat for improved accuracy."

on the same subject but a different barrel...shooting 5.56 in my TC Contender shows signs of excessive pressure....somewhat sticky opening and a very large muzzle flash....I find .223 which is what it is chambered for works better and "feels" better. I have a letter from TC dated 12/83 that says there is no problem firing either in a Contender.

Several MFGs mark barrels .223 but actually cut the chambers Wylde or 5.56. (ruger minis are one example... the mini "target" model is the only one with a true .223 chamber; all others accept 5.56 without issue).

Call the MFG.

madcratebuilder said:

Lot of FAIL in this thread.

READ.

http://www.ar15.com/ammo/project/AmmoOracle_061808.pdf

Important part.

Click to expand...

That's all well...but look at the LuckyGunner test as a counterbalance to that just-by-the-numbers statement, which measured the features of several examples of different 5.56, .223, and Wylde chambers. The important point of comparison in that data is that the variances in measurements between the different makers and examples within a single chamber design that were all over the map, including dimensions that overlapped into the other chamber design measurements.

Bottom line: the discussion is just not as simple as quoting the 'ammo oracle'.

If it won't, get it fixed: barrel->gunsmith+correct chamber reamer= /problem.

My Remington 700 in .223 had a very long throat. In this lawyer laden country, I'd almost bet that all production .223 barrels have a similar chamber.

I'll throw my story in-you decide.

I bought several parts kits and assembled them on lower receivers. I also have 1 Colt AR. ALL the barrels are marked 5.56. I had pressure trouble with hotter loads in my kit guns but no problem whatsoever in the Colt.

I added heavier buffers, heavier springs, on and on. Things improved, but the problems were still there. Finally I sunk some money into a Christensen reamer from Michiguns. I ran it through every barrel and it removed a surprising amount of metal from all the kit guns that were ALLEGEDLY chambered to 5.56. Only the Colt passed the reamer test with NO removal of metal. Now ALL my AR's have no problems with 5.56 ammo. What more can I say? There IS a difference in the chamber and it has a very noticeable effect on performance--especially in carbine length barrels. YMMV