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I have a Colt AR15-A2 that is marked .223.What damage can you do to the gun by shooting .556 ammo in it? What would it take to be able to shoot .556 ?
Thanx in advance

A 5.56 round creates much higher pressures than a .223 round. If the barrel is not marked 5.56 NATO, do not use 5.56 ammo in it. Use only .223.

The 5.56 barrel has a slightly longer throat so the bullet has to travel a short distance before engaging the lands and leads.

Here's a good article from last months Guns magazine that explains in detail.

http://www.gunsmagazine.com/twists-and-leads/" onclick="window.open(this.href);return false;

J Wilson wrote:I have a Colt AR15-A2 that is marked .223.What damage can you do to the gun by shooting .556 ammo in it? What would it take to be able to shoot .556 ?
Thanx in advance

Do NOT shoot 5.56 NATO in a gun proofed for .223. However, you may safely fire .223 in a gun proofed for 5.56.

J Wilson wrote:What would it take to be able to shoot .556 ?
Thanx in advance

Change the barrel its not that expensive and can be done yourself.

Sputz

Unless it is a match version it is chambered for 5.56... it is a colt. Only their match guns are .223 only. I would bank on that.

J Wilson wrote:I have a Colt AR15-A2 that is marked .223.What damage can you do to the gun by shooting .556 ammo in it? What would it take to be able to shoot .556 ?
Thanx in advance

One thing occurs to me..... WHERE is it marked ".223?" If it's marked on the lower receiver, that might not mean anything. What you want to see is what's marked on the barrel itself—and that may be hidden under the handguard. If it's a standard plastic handguard, or something like the Magpul MOE handguard, it will pop right off with the application of a little elbow grease. An inexpensive rail system like the UTG carbine length setup will also pop off the same way. But a more expensive free-floating rail system/handguard will be harder to remove. In any case, if you can expose the chamber end of the barrel, you should be able to find a proof stamp stating the actual caliber. Below are some pictures of what you should be looking for:

Here's an FN manufactured barrel:


A Bravo Company Mfg barrel:


A Daniel Defense barrel:


If your barrel is marked something like one of these, then you don't have anything to worry about. And actually, like JeepGuy79, some manufacturers will call their rifle a .223, but it is really a 5.56 NATO rifle. I had a Bushmaster like that once.

My AR-15 was built by a manufacturer and its marked: Cal. MULTI

Nothing on the barrel that I can see.

I'm assuming that either .223 or 5.56 would be acceptable.

LabRat wrote:My AR-15 was built by a manufacturer and its marked: Cal. MULTI

Nothing on the barrel that I can see.

I'm assuming that either .223 or 5.56 would be acceptable.

The barrel will tell you which round its throated for in that case. The lower receiver is likely what is labeled MULTI and that is so you can use it for other caliber builds but its an aesthetics thing. Your barrel will be throated for either 556 or 223, unless you went with something like a Wylde profile or the like.

LabRat wrote:My AR-15 was built by a manufacturer and its marked: Cal. MULTI

Nothing on the barrel that I can see.

I'm assuming that either .223 or 5.56 would be acceptable.

I believe that "Multi" stamp is on the lower receiver. And again I believe that Multi stamp means the lower receiver will work with 9mm or other pistol calibers. This has nothing to do with the barrel.

5.56 is never acceptable in a barrel stamped .223.

The Annoyed Man wrote:One thing occurs to me..... WHERE is it marked ".223?" If it's marked on the lower receiver, that might not mean anything. What you want to see is what's marked on the barrel itself—and that may be hidden under the handguard.

Ditto - the barrel is what you pay attention to - my Colt Match HBAR is marked .223 on the lower and 5.56 NATO on the barrel - it will shoot both.

Oh yeah, I said something wrong up there maybe. some Colt match barrels are 5.56 of course. I meant by my previous post if you pick up a colt m16/ar15 that is not a match barrel gun bet on a 5.56 chamber. Some match barrels are .223 only. I have yet to see a colt with a 223 not a match. There. that is right.

Hi to everyone,

Thanks for the feedback.

I've sent an email to the manufacturer to see what they say.
Will post any update I receive.

Labrat

Quick response:

Chambered in 5.56 so either 5.56 or .223 is good to go.

LabRat

LabRat,
Glad you got your question answered.Still have to take mine apart and look at the barrel.

J Wilson wrote:LabRat,
Glad you got your question answered.Still have to take mine apart and look at the barrel.

Unless I'm wrong, back me up one this one guys, you shouldn't have to take it apart. It should be clearly visible on the barrel near the end where the bullets come out.