Twist rate is only one factor for using heavier bullets or shooting long range. If you are shooting at 300 yards, which is about max for a .223 while hunting large coyotes, the need for heavy bullets diminishes. I do use up to 65gr. 63gr Sierra semi pointed spitzers are a great 300 yard bullet, but so is the Barnes 53gr x bullet. For vermin almost any well constructed 55gr will do the trick. Out of a mini 14 I doubt you will be shooting past 150 yards no matter what mods Ruger has made. IMHO.