I've built a few ARs. I built one as a "varmint" rifle with a 22" SS Wilson bull barrel. 1/8 twist. Another was built as a 3- gun rifle with a Latitude Armory 18" standard profile barrel. 1/7 twist. Both were chambered in 223 Wilde. The 3-gun rifle shot and continues to shoot better groups. I traded the varmint gun. I have a .556 14 1/2" 1/8 pencil barrel that shoots almost as well. Lessons learned.