.223 Rem vs. 5.56mm Nato
by Jerry Kraus
What is the biggest difference between AR-15 .223 and Mil-Spec 5.56mm chambers? Most people do not know; they say, “I think you can shoot both kinds of ammo through either one, right?”
Then, they buy an AR-15 and start to get more educated. Frequently, they later have regrets they did not get the AR with a chamber they wanted because they did not know what to ask.
We are going to cover the major options in AR-15 chambers, including Mil-Spec chambers and the benefits of each. I am going to limit this to .223 Rem. and 5.56mm chambers and will address ARs with other calibers, such as .308 (7.62×51 NATO), in the future.
There are three types of chambers in the M16/M4/AR-15/MSR family of rifles, but most people think there are only two.
- The first is the Mil-Spec 5.56mm chamber, which is used in the M16 and M4.
- The second is the .223 chamber, the most common chamber in AR-15 rifles, although you can get AR-15s with a 5.56mm chamber (why you would want that is very interesting and I go into that in detail below).
- The third is a .223 Match chamber, which is used in AR-15s by serious competitive AR-15 shooters.
There’s another that I have mine chambered in .223 Wylde- shoots .223 & 5.56 well
Was informed by more than one gunsmith that if your rifle is stamped 5.56 NATO you can safely shoot either a ,223 or 5.56 without doing any damage! If the barrel is stamped .223 and you shoot both, you will damage the barrel after usage of 5.56! Look at the barrel, read the manual, ask a gunsmith! Mine is stamped 5.56 NATO so I can safely shoot either!
This article is written from actual independent testing.
http://www.luckygunner.com/labs/5-56-vs-223/