Measure your twist with a patch on a rod, a ruler and a magic marker. I would suspect you have the 1 in 12.
The PRIMARY thing that affects the accuracy of the 223 is pressure on the gun. I am talking about where and how you hold it, what it is rested against or on and how tight the forend is.
My 223 will shoot 40, 45, 50 52, 55 grain bullets with equal accuracy. I am talking about quality bullets and my reloads. I would never expect MOA using surplus ammo or imported ammo. I also broke in the barrel....... 1 shot cleaned, i shot cleaned up to the first 10 rounds, then every 5 rounds. My gun does like a few fouling shots after a cleaning but it is a tack driver out to 250 yards.
I guess my point is to eliminate all the variables before you blame the ammo.