Once again I'm forced to ask the age old question. Can I run 5.56 through my Sporter. This is an eggs are good for you now they're bad for you, butter bad for you now its good for you circle jerk. My rifle is stamped 223 but the barrel is stamped 5.56. Never, ever popped a primer, never an over-expanded casing. I've never used anything but 52gr. hollows and 55gr ball. Why does someone selling me ammo, who's never fired my rifle keep telling me I cant. Once again, am I missing something. I already know the dif. pressure wise on the 5.56, and casing density. Can anyone tell me if my 20" gov. barrel is different or have I just been lucky so far.

In almost all cases, you go off the barrel markings.  If it says "5.56/5.56mm/5.56mm NATO" then you should be good.  I'd be interested to get a serious Colt guy in here to ensure everything is okay -you don't know what you don't know.  For all I know Colt may have marked their barrels a certain way, but it could be one of those "well at that time they did THIS" kind of things: I doubt the barrel would be .223 only if it's marked 5.56 unless some strange Coltism was afoot at the time.

All Colt barrels are chambered for 5.56 ammo you are good. The .223 stamp on your lower means nothing all that matters is what is stamped on the barrel.
I only run 5.56 through my Colts who ever is telling you that you can't knows nothing about AR's.

Thank You Gentleman I shall NEVER bring this up again.

Unless you have an older colt that only has the markings C MP B or C MP Chrome bore.

Even still I believe these are 5.56 rated also, even though the lower says .223.

Check the barrel as stated to be sure. Here is mine.


.223 on the lower



5.56 on the barrel

Thre round doesn't go into a chamber in the LOWER.......

GTG for 5.56....   Says so right on the barrel.

All Sporter 1s, in fact all Colt ARs have always been chambered for 5.56mm