Ok just starting to look into the AR platform and I'm looking to be educated here.I see AR's chambered in .223 and 5.56mm. I also see .223/5.56mm. Now it's my understanding that 5.56 round has a higher pressure than a .223 round. So it is not safe to fire 5.56mm in a .223 chambered AR. While you can fire a .223 in a 5.56mm chambered gun but with less accurracy. Is this correct? What do most of you guys shoot?