The 223 has a 1in9" twist
I had a .223 Savage 12FCP with a 24" 1:9 barrel. It shot 55gr FMJ to 77gr FGMM out to 500yds without any evidence of destabilization. I got my best results with 68gr Black Hills (i usually bought the remanufactured, Black Hills Remanufactured Ammo 223 Remington 68 Grain Match Hollow ), with FGMM 77gr a close second. As expected, I was was the weakest link.