I purchased my first AR type rifle today. It's a Colt Match Target M4 Carbine. Can I shoot 5.56 with this? The lower is stamped Cal. 223, the barrel says 5.56, and the box says Colt M4 5.56. I thought I read somewhere on here that all Colts are chambered for 5.56 but now I'm a little confused because the lower is stamped 223. Of course the dealer was of no help. Can someone please clear this up for me? Thanks in advance.

What's stamped on the barrel is usually the indicator of the chambering of the firearm, seems that 5.56 is your rifles caliber

5.56 is good to go.

Mail it to me with a bunch of ammo, and I'll test it for you.  

Like the posts above, 5.56 will work, your biggest problem is finding 5.56 to feed it.

Trust the barrel...the ammo goes through it so it won't steer you wrong

Well said, and absolutely correct

I have put many trouble-free cases worth of 5.56 XM193 and TAP OTMs through my two MT6400Cs. Your new pony will happily eat whatever you choose to feed it-5.56 or 223.

Enjoy your new M4-you're in for an awful lot of fun.




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Especially since it's a Colt

And a very expensive addiction.  But I can save you!  Just send your rifle to me - trust me, it would be a whole lot cheaper in the long run.

I love my 6400c! (it's been modified a bit)

To further clarify things for RustyPelican,

The .223 Remington and the 5.56 NATO cartridges are extremely simliar cartridges but not quite the same.  This does not GENERALLY prohibit one cartridge being used in the other chamber.

Essentially, without getting into 50 years of history and making things really confusing, the .223 Remington was the direct, developmental predecessor for the cartridge that became the 5.56 NATO cartridge.


As the adoption process went along its' merry way, the dimensions for brass and chambers were finalized to specs that are just a wee beit different.  Essentially the NATO cartridge is a wee bit "beefier" dimensionally.  In your average autoloading rifle the difference is negligable.

Now, when you get to bolt guns or rifles with Match chambers....then it becomes more important to know which cartridge you truly need to be using.  Using 5.56 NATO in a .223 Remington rifle with a tight or Match chamber can be courting high pressures and very difficult extraction.  This is because the dimensional profile of the 5.56 NATO is slightly large in certain areas, mostly concerned with the case neck and should dimensions.

As far as your Match Target, it is listed as .223 on the reciever but the actual barrel is chambered to the 5.56 NATO dimensions.  Since the dimensions of the civilian counterpart, the .223  technically fall INSIDE the dimensions of the 5.56 NATO, you can use either cartridge interchangeably.

So...in short....go shooting and go have some fun.

5.56 NATO is what your chambered for. Barrels marked 5.56 CAN also shoot .223. Barrels marked .223 CANNOT shoot 5.56.

So you are perfectly good to go with either

but .223 is easier to get when the ammo aile at walmart hasn't been stripped bare