Here are the choices Hart offers: Twist rate options: 6 Groove in 8", 9", 10" or 12"; 5 Groove in 8" Contours: Douglas 2, 3, 4, 5, and 5.5 or Remington Varmint, Mag, ADL/BDL, Mountain Taper I have no idea about the pros/cons of 6 vs 5 grooves. I shoot mostly Nosler and Barnes bullets. Their load data indicates 9" twist, except Barnes recommends 8" for the 168 gr LRX. I don't know if I'll ever use that bullet, but what is the downside of going with 8" instead of 9"? Finally, those contours mean nothing to me. I'd like a sporter weight barrel. Not so heavy that it's a pain to carry and not so light that barrel heating makes it a chore to work on loads for the rifle. Finally, straight 6 groove fluting is available for $120. Other fluting profiles are available for $180. Flute it or not? What would you do?