Randy as mentioned A 5.56 will fit in a 223 Chamber but it can cause an over pressure issue. A 5.56 chamber will work just fine with both.

What cliber it says on an AR lower doesn't mean much. The issue is what the barrel and upper is. Most of mine say multi cal.

I can slap a variety of uppers on the same lower receiver from a 9mm to a 50 Beowolf.