.223 vs. 5.56 rounds?
Can anybody tell me what the difference is between the .223 round and the 5.56?
I know that the 5.56 is rated at a higher pressure and the chambers are different (the 5.56 chamber has a longer leade (I think it is called, but am not sure what it really is).
My question has to do with the ammunition itself. Are the .223 and 5.56 dimensionally the same? Does the 5.56 have more powder or powder with a different burn rate? What is it that makes the 5.56 have higher pressure, and thus makes it unwise to use in a weapon chambered for .223 while you can use .223 in a weapon chambered for 5.56?
I am curious because I am seeing four different things:
1. What people say – use .223 in a 5.56 chambered weapon but NEVER the other way around.
2. SAAMI rating.
3. NATO EPVAT ratings (which is measured in a different location than SAAMI so I am not sure how the two correlate).
4. CIP (which also defines the chamber specifications for .223 as being different than the 5.56, but defines the “maximum service and proof test pressure” of the .223 as being equal to the 5.56)
The whole reason that this has come up for me is that I am having a rifle rebarrelled and the gunsmith said I would have to go with .223 in order to get the accuracy guarantee, but that it would not hurt it to run 5.56 thru it occasionally.
So, if anybody can tell me what the difference is between the .223 and the 5.56 ammo itself, I would greatly appreciate it.