A timely post, I was just wondering about this myself.
I looked in my Mini-14 instruction manual, it says this: "The Ruger Mini-14 Rifles are chambered for the .223 Remington (5.56mm) cartridge. The Mini-14 Rifle is designed to use either standardized U.S. military, or factory loaded sporting .223 (5.56mm) cartridges manufactured in accordance with U.S industry practice."
Sounds like "both" to me !!