.223 twist

[Catfish]

Each barrel is different. Some do as they are suposed to and others not quite. I had a 1 in 14 twist that did pretty well with 55 gn. bullets. By that I mean it would shoot abt. 3/4 moa and some times better. A 12 twist should shoot 55 pertty well, but you`ll not be sure untill you try them. I`m sure that barrel harmonics figures in the equation, I just don`t know how. I would guess that the flat base 55`s will shoot better than a boat tail bullet though.