5.56x45 or .223rem?

[meatyrem]

I have a question about rifles in the .223 rem and the 5.56x45 NATO. Can they both be shot out of the same rifle? For example; Ar 15 chambered in the NATO round, can that fire the .223 rem also? Or vice versa? There is a question that a rifle chambered in one cannot shoot the other. If I remember correctly, a rifle chambered in 5.56 NATO can shoot both, but a rifle chambered in the .223 rem cannot shoot the NATO round. Just looking for clarification on this issue. Thanks for any help.

Meatyrem

[Trickymissfit]

the rounds are the same (case), but the throats are slightly different. You'll see a very slight pressure spike (I mean very slight).
gary

[meatyrem]

I was always on the assumption that either one can be fired through a rifle chambered in a 5.56 NATO. And either one can be fired through a rifle chambered in .223 rem. There is a fella that said one will fire both but not the other way around. So if there is a slight difference, then will it harm the rifle in any way? Or should it be avoided just to be safe?

[Trickymissfit]

Originally Posted by meatyrem

I was always on the assumption that either one can be fired through a rifle chambered in a 5.56 NATO. And either one can be fired through a rifle chambered in .223 rem. There is a fella that said one will fire both but not the other way around. So if there is a slight difference, then will it harm the rifle in any way? Or should it be avoided just to be safe?

without chamber and throat drawings right in front of me, I can't exactly tell you the difference. But I do know it's in the length and angle of the throat. If I remember right the 5.56 is a few thousandths longer in the throat, but with a wider throat angle (I'm sure somebody will correct me). Sorta like a very short free bore. But the cartridge case and length are the same
gary