can my ar 15 shoot 5.56?


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Johnny Lightning
March 26, 2013, 04:22 PM
I have a bushmaster lower that can shoot both .223 and 5.56 but the rock river upper is the question. I took the hand guards off to find out if there is anything written on the barrel but the only markings are 200C/K? There is a keyhole marking on the upper receiver also but that's all I can find. Thanks for the help!

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jmr40
March 26, 2013, 04:31 PM
223 and 5.56 are completely interchangeable.

Certaindeaf
March 26, 2013, 04:33 PM
Except someone is going to cite a tome how they are not.

RainDodger
March 26, 2013, 04:37 PM
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.

Rom828
March 26, 2013, 04:40 PM
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.

silicosys4
March 26, 2013, 04:52 PM
Except someone is going to cite a tome how they are not.

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

Bill4282
March 26, 2013, 04:53 PM
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.

C-grunt
March 26, 2013, 05:13 PM
Many of the Bushmasters we had at work would pop primers when we shot M193 for one qual course.

adelbridge
March 26, 2013, 08:02 PM
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.

firesky101
March 26, 2013, 08:02 PM
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.

paulo
March 26, 2013, 08:08 PM
Make sure it's not a Wilde cut chamber.

rust collector
March 26, 2013, 08:19 PM
That's its purpose in life--accuracy coupled with safety. If your gun has a Wylde chamber, you are gtg.

Nato chambers are designed to ease extraction and function. Nato brass tends to be thicker to stand up to more punishment, but that means you start with a lighter load. There is a difference, it is often overblown, but get the real story and don't rely on scuttlebutt.

Hacker15E
March 26, 2013, 08:25 PM
http://www.luckygunner.com/labs/5-56-vs-223/

madcratebuilder
March 27, 2013, 10:38 AM
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.

Creature
March 27, 2013, 10:42 AM
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.

Concur.

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

taliv
March 27, 2013, 10:49 AM
i think it's been covered pretty well above, but just consider the real problem is likely to come from stacking issues. shooting 556 in your nice clean 223 chamber off a bench is probably not going to blow up. but add a little dirt or a little rain. or a fast firing schedule like a carbine class that gets the gun hot. and then that one round that is a little hotter.

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.

col_temp
March 28, 2013, 01:38 PM
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.

Good point.

hentown
March 28, 2013, 04:48 PM
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. ;)

SwampWolf
March 29, 2013, 03:43 PM
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."

Fleetman
March 29, 2013, 03:59 PM
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.

1KPerDay
March 29, 2013, 04:30 PM
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.

Hacker15E
March 29, 2013, 06:41 PM
Lot of FAIL in this thread.

READ.

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

Important part.

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'.

sixgunner455
March 29, 2013, 06:55 PM
If it won't, get it fixed: barrel->gunsmith+correct chamber reamer= /problem.

Coop45
March 29, 2013, 07:23 PM
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.

mtrmn
March 29, 2013, 08:12 PM
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

ObsidianOne
March 29, 2013, 08:42 PM
223 and 5.56 are completely interchangeable.
Dangerous advice. If a gun is marked .223, best to ask the manufacturer. While most of the time they do interchange, the max pressures for 5.56 are almost 8,000 psi higher.
Some guns, such as a certain model of the Ruger Mini 14, some competition model, is NOT setup to shoot 5.56 and can ONLY shoot .223. Save a gun, life, or limb, call the manufacturer.

SwampWolf
March 31, 2013, 07:58 PM
Some guns, such as a certain model of the Ruger Mini 14, some competition model, is NOT setup to shoot 5.56 and can ONLY shoot .223.

ObsidianOne: I've never heard of a Ruger Mini 14 rifle that will not shoot 5.56 ammunition safely. Please provide verification of this "allegation". Thank you.

firesky101
March 31, 2013, 10:53 PM
ObsidianOne: I've never heard of a Ruger Mini 14 rifle that will not shoot 5.56 ammunition safely. Please provide verification of this "allegation". Thank you.
A quick browsing of Ruger.com shows most mini-14's as .223/5.56, however the target models only say .223.

Warp
March 31, 2013, 10:55 PM
223 and 5.56 are completely interchangeable.

No, they most certainly are not.

.223 in a 5.56 chambered firearm, yes.

5.56 in a .223 chambered firearm...best to avoid.

balderclev
April 1, 2013, 02:31 AM
If you are shooting 556 in a Mini-14 or AR-15 you should be fine. They have sloppy actions. A bolt gun is not the same. Shooting 556 in a bolt gun chambered for 223 will sometimes cause difficulty in chambering.

winterhorse290
April 1, 2013, 09:03 AM
seems strange. i can order .223 reloading dies all day long but have never seen 5.56 dies for sale.

cfullgraf
April 1, 2013, 09:09 AM
seems strange. i can order .223 reloading dies all day long but have never seen 5.56 dies for sale.

Dimensionally, 223 Remington and 5.56 NATO cases are identical.

The differences come from what is in the case and the chambers.

Warp
April 1, 2013, 09:15 AM
http://www.luckygunner.com/labs/5-56-vs-223/

Carl N. Brown
April 1, 2013, 12:25 PM
.223 Remington has SAAMI spex established 1962. SAAMI = Sporting Arms and Ammunition Manufacturers Institute (the European equivalent is CIP Commission Internationale Permanente pour l'Epreuve des Armes Feu Portatives ). CIP has standards for .223 Remington are similar to SAAMI but slightly different too. I suspect .223 Remington sporting spex are tailored for bolt action rifles. (I could be wrong and someone will tell me I am.)

Military contracts determine the specification of 5.56x45mm ammunition which includes the pressure level at the gas port for semi or full automatic firearms. Each different contract.

My understanding is that the main difference between .223 and 5.56mm arms and ammo is the chamber dimensions (particularly the throat or leade where the bulllet enters the rifling) and the rate of twist in the barrel.

I have heard most .223 barrels are usually throated for bullets in the 36 to 55 grain range, with twist rate of 1 turn in 12 inches, whereas most 5.56mm NATO is throated for bullets in the 55 to 62 grain range, with typical twist rate 1-in-9 although the first M16 and AR15 rifles were 1-in-12 for the 55 grain.

Firing the heavier bullets in chambers with shorter leade can cause pressure to go up. Same precaution as loading highpower rifle cartridges with bullets that touch or enter the rifling. Watch the primers for excess pressure signs: if they are observed, stop. True for any caliber, any gun, any lot of ammo.

I also have heard that for countries that forbid military calibers, firearms are often marked .223 Remington rather than 5.56 NATO with no real difference.

PLUS there are some AR or Mini14 barrels marked .223 that are truly .223 Remington, but many are actually identical to 5.56mm NATO.

It's like using +P in a revolver: you won't know for sure unless you ask the manufacturer if the gun or barrel was made for it.

I have treated .223 and 5.56 ammo factory loaded with 55 grain FMJ as equivalent. Some will tell me not to worry, others will advise me to make sure I have good insurance.

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