Ruger claims a NATO chamberYour AR maybe a Wylde if not most more than likely 5.56 Nato. It should be marked on the barrel (maybe even the twist rate) also in your original post "AR 5.56" so it probably is 5.56 Nato, fire away and enjoy
-Rock
Some manufacturers show Wylde chambers also my early mini 14(s) show 223 Rem, and some early AR's show 223 Rem. So in that regards, something to keep in mind when you buy an older Mini-14 / AR
You'll have to clean up afterwards.I just came into possession of several hundred rounds of 223.
I have a new Ar 556 I'm still "getting to know"
Is there a down side to running this through at the range?
Not for defensive purposes
Thanks