.223 and 5.56

[Veracity]

Gentlemen,

Forgive me, I might not know enough about it to phrase the question properly.

Can someone explain here....or link me to a proper explanation of why some rifles can shoot .223 but not 5.56? (Or is it the other way around?)

I've got a 6920, 6400C, Colt 20" MT HBAR, and a BM. Only one of the Colts has been fired...and it's had less than 100 rounds put through it so far. Some Remington .223 55gr and some PMC .223 55gr.

I know the Colts are good to go with 5.56, but does that also mean I can shoot .223 in them?

All I've got now is XM 193 and TAP....so I know I'm safe with the Colts.

Thoughts?

[hatt]

5.56 is generally loaded to a higher pressure than 223. 223 is fine in a 5.56 gun, it's the 5.56 which may pose a problem with 223 guns or even some out of spec 5.56 guns. You will be fine with your Colt's in this aspect. I'm not aware of the state of BM chambers.