Bushmaster 5.56 = .223? (found out answer)

[thejanitor]

Just saw an ad for a Bushmaster 5.56 Nato, are these Cartridges interchangable with .223 Rem in a Bushmaster?
Thanks thejanitor
EDIT-
OK I read online they are not equal but the reciever stamped 5.56 Nato can shoot .223 just may not be as accurate, but a gun stamped .223 shouldn't shoot 5.56 unless MFG says ok. Throat length can be too short causing chamber preasure to exceed SAAMI numbers..... So thats what I needed to find out.
thejanitor

[CannonKrazy]

The short answer is Yes. Most all of the currently made ARs are stamped 5.56/.223. Meaning that either round can be fired in the rifle.  There are many of the older models that were chambered and marked as 5.56 only.

[corbanzo]

If it is marked 5.56 then it will shoot .223 just fine, interchangeably.  If it is marked .223, it might have some ejection problems with 5.56 ammo, due to the cartridge being just lightly thicker, the dimensions are so very close to the same, that chambering a 5.56 in a .223 shouldn't be a problem, but could cause performance issues. 

.223 specific AR barrels are pretty few and far between though... usually only for match or long distance type uses. 

[emsemt911]

my 5.56 barrel shoots the .223 ammo more accuratly.
I believe it is because the .223 has less powder than 5.56 loaded
ammo