Dumb .223 Rifle Questions

Am beginning to learn about .223 AR type gadgets, so perhaps will ask multiple dumb questions soon.

For starters, is there a difference between .223 Rem versus 5.56mm ammo for these things?

I could google rather than asking, but one time it took a bit of searching to confidently determine that .380 Auto is the same as .380 ACP, so a dumb question may be quicker. Sometimes experts assume that everyone knows the answer to such trivia.

James C Chandler Jr said:
...is there a difference between .223 Rem versus 5.56mm ammo for these things?

James,

There is no practical difference. The .223 Remington cartridge is the civilian version of the 5.56 mm NATO round. This relationship is similar to the .308 Winchester round being the civilian version of the 7.62 mm NATO round. In both situations, the civilian round and military round are interchangeable in a rifle chambered for that cartridge.

For more information, look here: http://en.wikipedia.org/wiki/5.56x45mm_NATO

James -

I don't have an AR-style rifle, but there are some minor differences according to this thread on the Smith and Wesson Forum.

http://smith-wessonforum.com/eve/forums/a/tpc/f/695107034/m/9221053443

One quote that stood out was--
"Generally speaking it is Ok to fire .223 in weapons chambered for 5.56 but not 5.56 in weapons chambered in .223."

I always thought they were interchangeable, but for safety sake, make sure you research the subject pretty thoroughly.

After reading the thread, I got pretty lost and told myself that if I EVER decide to get an assault rifle it'll be an M-14 in 7.62mm or a Ljungman AG-42 in 6.5mm.